(introduction...)

IETC - International Environmental Technology Centre

Prepared in collaboration with

Danish Hydraulic Institute

International Environmental Technology Centre, United Nations Environment Programme and Water Branch, United Nations Environment Programme

1998

Disclaimer:

Mention of technologies, processes, equipment, instruments or materials identified in this Source Book of Alternative Technologies for Freshwater Augmentation does not imply recommendation or endorsement by the United Nations Environment Programme (UNEP), its International Environmental Technology Centre (IETC), or its Water Branch, nor does it imply that these are necessarily the best available for the purpose. The opinions and views expressed in the document do not necessarily state or represent of UNEP, the IETC or the Water Branch.

IETC Technical Publication Series Issue 8
ISBN 92-807-1508-8b

Foreword

The countries of Asia have seen growing pressure on water resources, with increasing demand and costs, for agricultural, domestic and industrial consumption. This has brought about the need to maximize and augment the use of existing or unexploited sources of freshwater. There are many modem and traditional alternative technologies for improving the utility and augmenting the supply of water being employed in various countries, but with limited application elsewhere due to the lack of information transfer among water resources managers and planners.

The "Source Book of Alternative Technologies for Freshwater Augmentation in Some Countries in Asia" was prepared by the Danish Hydraulic Institute as part of the joint United Nations Environment Programme (UNEP) Water Branch and International Environmental Technology Centre (IETC) initiative to provide water resource managers and planners, especially in developing countries and in countries with economies in transition, with information on the range of technologies that have been developed and used in the various countries throughout the world. UNEP wishes to thank the Danish Hydraulic Institute and those individuals involved in the preparation of the Source Book. The final revision of the Source Book was assisted by V. Santiago, C. Strohmann, and E. Khaka from UNEP IETC and Water Branch, respectively.

This information was gathered through surveys carried out on a regional basis - in Africa, Western Asia, East and Central Europe, Latin America and the Caribbean, and Small Island Developing States. The results, including this Source Book, will be compiled into a Global Source Book on Alternative Technologies for Freshwater Augmentation to be used throughout the countries of the world.

It is hoped that the technologies summarized here will be useful in the sustainable development of the countries of Asia and other regions.

John Whitelaw
Director
International Environmental Technology Centre
United Nations Environment Programme

Terttu Melvasalo
Director
Water Branch
United Nations Environment Programme

1. The freshwater imperative

Water is basic to the human health, welfare and economic development. Water is equally vital for the preservation of wildlife and the natural environment. Freshwater is a central feature of climate, and can be a source of energy, an avenue of transportation, and a means of production and aesthetic inspiration. Its presence or absence governs the nature and placement of structures within the physical landscape and it exerts a major influence on demographic patterns. It is also viewed as a key to economic growth and prosperity.

Freshwater, or that portion of the world's water resources suitable for use by humans and most terrestrial vegetation and wildlife, is a small portion of the global water supply. For domestic and agricultural uses, freshwater generally refers to water containing less than 1 000 mg/l dissolved solids. (Although, depending on the specific purpose for which the water is used, this concentration may be higher or lower; for example, salinity levels in freshwater for drinking purposes should not exceed 500 mg/l, while, for irrigation purposes, they should be less than 2 000 mg/l.) The presence of other contaminants such as toxic substances, disease-causing organisms, nutrients, oxygen consuming substances, and suspended solids also decreases the quality of freshwater for human and environmental uses.

For centuries, this limited volume of freshwater has been augmented for different human purposes using various indigenous and modem technologies. Frederick (1992) points out that freshwater augmentation technologies in 1990 have advanced little in the several centuries since the early achievements of the Romans in transporting water over long distances and the Dutch in manipulating and regulating water levels. Likewise, in Asia, few advances are evident since the development of large irrigation projects in China's Sichuan Province, runoff farming collection systems in Israel's Negev Desert of Israel, and, in the rural areas of Thailand and Indonesia, the indigenous practices of rainwater collection, developed during the past several centuries.

The absolute shortage of freshwater is further compounded by the fact that freshwater is unevenly distributed geographically and seasonally. Thus, the need for augmentation technologies remains. Most recently, decades of water development and management policies have focussed on supply-side management with the construction of large reservoirs, dams and conveyance systems, as well as deep tubewells. Despite these technological advances in freshwater augmentation, the modem era is not only facing tremendous water scarcity, but also a shortage of the capital investment funds necessary to continue the scale of construction likely to be required in the future. Further, conservationists and NGOs are placing ever larger hurdles in the path of these modem water resources development projects, as the damages caused by many past projects have become obvious, even though the previous construction of hundreds of large and small dams and deep tubewells has contributed significantly to the overall well-being of the people and societies in the Asia (WRI, 1994).

This issue of water scarcity, and the associated cost of developing new water resources, has now been placed water at the top of the international agenda. The United Nations Commission on Sustainable Development (UNCSD), at its first meeting to review global progress in the implementation of the United Nations Conference on Environment and Development's (UNCED) Agenda 21, Chapter 18 (Freshwater Resources), called for a comprehensive assessment of global freshwater resources as an initial step in assessing the adequacy and suitability of the world's freshwaters for meeting current and future human demands. In the meantime, water resources managers have begun to focus increasingly on other methods of freshwater augmentation, including a return to the more traditional technologies developed throughout the world. This book, prepared by the United Nations Environment Programme's (UNEP) International Environmental Technology Centre and Water Branch, provides a catalogue of technologies traditionally and currently used in some countries of the Asian region, as an initial step in compiling a global source book on freshwater augmentation technologies. This book is one of five such volumes prepared by UNEP in support of Agenda 21, Chapter 18 and Chapter 34, the latter presenting a detailed plan of action for the assessment and transfer of technologies worldwide.

The per capita water availability in Asia and the Pacific Region varies widely. A recent report of the United Nations Economic and Social Commission for Asia and the Pacific (ESCAP) on the State of the Environment in Asia and Pacific (1995 Draft) pointed out that:

The per capita water availability varies from as high as 200 000 cubic metres in Papua New Guinea to 3 000 cubic metres in Afghanistan, China, India, Korea, Pakistan and Sri Lanka. Countries like Afghanistan, Pakistan and semi-arid regions of Northwest India and Northwest China face growing water scarcities. Likewise, due to growing uncertainty of rainfall and high population growth, local scarcities are increasing in several major cities; e.g., Beijing, Jakarta, Karachi, Madras and Kathmandu.

The increasing water resource scarcity has already affected the water supplies in major cities of Asia. Of 38 major cities, only 21 cities have full water supply services. Others have already faced rationing of water supplies. While cities like Lahore, Jakarta and Manila provide 16 to 20 hours of service per day, Delhi, Rangoon, Karachi, Dhaka, Bombay, Calcutta, Madras and Kathmandu provide only between 1 and 10 hours of service per day (ADB, 1993).

The environmental costs of intensive water development are also escalating. Many coastal communities are facing upstream saltwater intrusions in river systems which threaten their drinking water supply (Postel, 1985). Wasteful use and poor management of water resources impose serious costs as well. Some detailed information available indicate that:

· in the 28 years between 1960-1988, portions of the City of Bangkok have sunk about 1.6 m and the current rate of subsidence for some sections of the City is about 5 cm/year (Phantumvanit et al., 1990).

· heavy pumping for irrigation purposes has caused a drop in groundwater levels of 25 to 30 m in a decade in Tamil Nadu, India (Postel, 1985), and of about 7 to 10 m in Gujarat, India, over a 21 year period between 1966-1981 (Ghosh and Phadtare, 1990).

· in Madhya Pradesh, India, extensive waterlogging of soils due to historic agricultural practices have caused farmers to refer to their once fertile lands as "wet deserts" (Postel, 1985).

· groundwater overdrafts in the northern provinces of China, typified by annual pumping volumes in Beijing that exceed the sustainable supply by 25%, have caused water tables in some areas to drop by up to 4 m/year, and, in Tianjin, by 20 cm every year (Postel, 1985).

A further dimension of the problem is a result of the decreasing assimilative capacities of the rivers and waterbodies in major urban areas. Freshwater used for consumption and production processes are typically drained as wastewater to surface water courses. Usually, during the dry season, these waterbodies are often loaded with sewage and effluent in amounts greater than their carrying capacity. In such situations, water availability is not only constrained due to physical limits, but also due to deterioration in water quality. The Human Development Report (UNDP, 1992) indicated that the majority of the population in developing countries still lack safe drinking water and that more than 50% of the population have no access to potable water.

The unit production cost of water in public water supply systems in the major cities of Asia varies from about $0.01/m³ in Hanoi to about $0.32/m³ in Hong Kong. Nearly 70% of water supply utilities have unit costs below $0.10/m³. The average tariff, estimated from annual water bills in 38 major cities of Asia, ranged from about $0.01/m³ in Shanghai to about $0.47/m³ in Port Vila, with a median tariff of $0.44/m³. However, both the unit production cost and tariff rates do not include the social cost of production or scarcity or opportunity costs of the water. In addition, these costs suggest that water augmentation efforts of the past have largely neglected the environmental costs of rates of withdrawal of available freshwater that exceed rates of replenishment. Indeed, such relatively low costs have encouraged this rapid rate of depletion of water resources in many urban areas.

The costs of water supplied by municipal systems in some urban areas, however, have already started to rise. In the Bangkok Metropolitan Area, the real, per unit rate of water consumed has almost doubled between 1976 and 1989, while the per unit supply cost to the consumer has increased by two and one-half times. The economic costs of groundwater depletion in Bangkok City are realized in the increased costs of pumping water as ground water levels recede, and the costs of providing surface water to substitute for groundwater that has become saline. In addition, there are other costs of too high a rate of water withdrawal, including the costs of land subsidence and related costs of damages to structures, streets, and underground water, sewer, electric and telephone lines, and an increased risk of damage from flooding (Phantumvanit et al, 1990).

In Thailand, the marginal construction costs of all types of irrigation systems installed between 1978 and 1990, rose until the mid-1980s, but declined thereafter in response to a decline in the incremental area brought under irrigation. An economic evaluation of irrigation systems constructed during this period indicated that scarcity, and high rental and opportunity costs contributed to the decline in new irrigation areas (Tiwari, 1994).

In The Philippines, the cost of water supplied to the agricultural sector has declined over the nine year period from 1975 to 1984. Water fees for irrigation water supplied from groundwater sources decreased from $36/ha to $23/ha, and, for irrigation water supplied from surface water sources, from $36/ha to $14/ha. However, as the water service fees for irrigation water in The Philippines and most other developing countries are not based on the marginal value of water, these prices and trends clearly do not reflect the scarcity value of water in The Philippines or these other countries.

Despite the water shortages in many parts of Asia and other constraints, no incentive mechanisms are currently being actively promoted, either for the conservation of available water or for the technological innovations for augmenting and conserving water in future. Supply side management, dominated by a command-and-control approach, has long dominated the field of water resources management, and the increasingly significant environmental dimensions of the water supply problems have been neglected.

The persistence of water scarcity problems in many countries of Asia suggests two major areas for concentration in terms of freshwater augmentation technologies. First, decision-making criteria, presently based on engineering and pure economic grounds, should be shifted towards a more comprehensive, decentralized and participatory type of management system. Development efforts also should be carried out in an environmentally sound and sustainable way. This requires an integrated approach rather than the continuation of conventional practices.

Second, it is time to look for traditional, low-cost water collection and use systems, which have been practised for centuries, as well as other technological options. Low-cost water collection systems, such as rainwater harvesting, conservation of freshwater through dual distribution system and alternative technological options, have to be perceived as sound bases for developing new sources of water. Technologies related to water conservation, including those concerned with quality and standards, can have long-term impacts on the availability and capacity of traditional sources of water to supply freshwater for human uses (Keenan, 1992). This, no doubt, will add additional costs to the development of new water resources, but can satisfy the need to maximize the use of existing water resources as well as augmentating such sources with previously unexploited water resources using both the modem and traditional techniques. These augmentation technologies include wastewater reuse, water recycling, desalination, dew harvesting, and fog and rainwater harvesting. Nevertheless, application of these technologies are still limited, mainly because of the lack of information on the appropriate technologies available (Table 1).

TABLE 1. Potential Water Quality Problems Related To Alternative Freshwater Augmentation Technologies.

		PROBABLE IMPACT ON WATER QUALITY
TECHNOLOGY		DRINKING WATER	AGRICULTURE	INDUSTRY
RAINWATER HARVESTING
	Erection of Bunds Around Agricultural Farms	-	No problem	-
	Low Lying Pond for Irrigation in Critical Periods	-	No problem	-
	Pond-Sand-Filter Process	Salinity and Iron
	Rain Water Harvesting from Roofs	No problem		No problem
	Open Sky Water Catchment	Hygiene
	Artificial Pond Catchment	Hygiene and salinity	-	Hygiene (food industry)
WATER CONSERVATION
	Recycling	Cultural problems	Hygiene	Depends o n industry and use
	Reduce Wastes	No problem	Salinisation	No problem
	Reduce Evapotranspiration	No problem	No problem	No problem
	Regulated Flow in Agriculture		No problem
ARTIFICIAL RECHARGE OF GROUND WATER
	Direct Subsurface Recharge	Hygiene and toxics	No problem (controls needed)	No problem (controls needed)
	Surface Recharge	No problem	No problem	No problem
DESALINATION		No problem
FOG, DEW AND SNOW HARVESTING		No problem (tastes)
REUSE OF WATER
	Reuse of Wastewater	-	Variable (controls needed)	-
	Reuse of Irrigation Water	-	Salinity
ALTERNATING USE OF SURFACE AND GROUND WATERS		Controls needed	Controls needed	Controls needed
NATURAL SPRINGS		Protection required	Excess water
ARTIFICIAL SAND/ROCK FIXES RESERVOIRS		Variable depending on source	Variable depending on source	Variable depending on source

2. Objectives

The main objective of this project is to address the need of Asian planners for information appropriate to maximize and augment available freshwater resources using appropriate technologies. To achieve this objective, it is necessary to provide water resource managers with information on different technologies used within the Region to augment and maximize freshwater resources, and on specific experiences with these technologies from throughout the Region. The Asian Source Book forms part of the UNEP environmental technology transfer initiative that will ultimately result in the preparation of a Global Source Book on Alternative Technologies for Freshwater Augmentation. Other regional source books are being compiled for Africa, Latin America and the Caribbean, East and Central Europe, West Asia, and Small Island Developing States. These regional books provide a basic source of information for, and form the basis for international cooperation between, developing countries of the world.

3. Organisation of the source book

This Source Book contains three main parts. Part A presents an overview of the survey results and identifies the need for the identification of freshwater augmentation technologies in the region. The status and current use of alternative technologies for freshwater augmentation in selected countries within the region are summarised based on information gathered during field surveys conducted during 1995. The methodologies used to obtain the information also are summarized, together with the results of the surveys, additional observations, conclusions, and recommendations about the technologies currently in use to augment freshwater resources. Part B, Alternative Technologies, presents a series of technology profiles which describe in greater detail the technologies currently in use to maximize water use efficiency and to augment freshwater supplies. The information provided in this part is based on an extensive literature review and the field surveys carried out in the region within four selected countries. The different technologies include water conservation, wastewater reuse, rainwater harvesting, artificial recharge of groundwater, and desalination technologies, amongst others. In addition to the technical description, each technology is analysed in terms of the extent of its use; its operation and maintenance; level of involvement; costs; effectiveness; suitability; cultural acceptability; advantages and disadvantages; and any further development of the technology that may be required. Part C contains information on selected case studies identified during the field surveys. The purpose of the case studies is to highlight especially innovative, cost effective technologies that have been successfully adopted within the region.

4. Survey methodology

The approach used in this study is based upon literature reviews, field surveys, and discussions with concerned individuals and professionals. An extensive review of the available literature was made by a group of water experts from the Asian Institute of Technology (AIT), Bangkok, Thailand. In addition to the literature available at the AIT library, information was collected from individuals from within the region. Much of the literature reviewed did not contain complete or quantitative information on the various technologies identified, and a significant portion of the available literature was only available in specific countries or from local sources (e.g., unpublished documents, internal papers, etc.), not readily accessible by the study team. Only references to freely available documents have been included.

Field surveys were carried out in Bangladesh, India, Nepal, and Thailand to supplement the results of the literature survey. The four countries were identified, during the initial phase of the study, as countries within Asia that were leading the region in the development and implementation of freshwater augmentation technologies. Within these four countries, various hydrological regions were identified that represent typical hydrological and social areas of Asia, excluding oil-rich west Asia. For example, the rainwater harvesting technologies used in northern and northeastern Thailand represent technologies that could be applied in the southern China and Indo-China regions. Similar climatic conditions also prevail in Laos, Cambodia and Vietnam. Likewise, the conditions in southern Thailand are similar to those in Malaysia, Myanmar, Singapore, and parts of Indonesia. Nepalese conditions represent those in the mountainous areas of the region (e.g., Afghanistan, Bhutan, China (Tibet), and northern areas of Pakistan and India), while the socio-economic conditions in Nepal are representative of those in the smaller, poorer countries of the region, with large rural populations. Conditions in India, a sub-continent with a wide range of physical, social, cultural and climatic characteristics, have relevance throughout Asia and outside. Likewise, the physical and tropical climatic conditions in Bangladesh are representative of many regions in Asia including Sri Lanka, Myanmar, Cambodia, and Vietnam. Local consultants carried out the field surveys and prepared the case studies in the different countries. The Danish Hydraulic Institute, Bangladesh Regional Office, in association with the Water Expert Group of AIT, coordinated the field survey and compiled the Source Book using information drawn from the country reports. These detailed country reports are available from the UNEP Water Branch, Nairobi, Kenya, together with additional information, photographs and illustrations of the various technologies.

The field surveys were carried out in three stages by survey/reconnaissance teams within each of the four representative countries in the region. In the first stage, information on the use, place of use, and characteristics of use of freshwater augmentation technologies was obtained from discussions with resource persons belonging to universities, research organizations, government departments and NGOs. The available literature on freshwater augmentation technologies was also reviewed. In the second stage, informed persons from government departments, research organizations, universities, and international organizations were consulted for more detailed information on the places and types of use of freshwater augmentation technologies. Finally, site-specific, detailed information was collected through a questionnaire survey and focussed group discussions. Questionnaire surveys of heads of households were conducted in randomly-selected individual households chosen from the total number of households within a specific settlement or village. Individuals included in the focussed group discussions included school teachers; members of the local councils; well known farmers, fishermen and industrialists; and representatives of farmers organisations, etc., as well as officials from organizations such as UNICEF and NGOs directly or indirectly connected with freshwater augmentation technologies.

At the conclusion of the field investigations, a Workshop and Expert Group meeting was organised in Kathmandu, Nepal, between 5 and 9 November 1995. In addition to the local consultants who conducted the field surveys, experts and others involved in water resources management and development from throughout Asia were invited to discuss the findings of the study. The Draft Source Book was reviewed and new ideas were received in four focal areas; namely, rainwater harvesting, water conservation and recycling, water quality improvement, and groundwater recharge. It should be noted that rainwater harvesting has been defined in its broadest sense as any process whereby (i) crops or plants are grown by exploiting runoff or directly impounded waters, (ii) human water needs are satisfied by waters drawn from catchments either within or outside an individual household, (iii) fish and other aquatic livestock are cultured using waters drawn from individual catchments or runoff, and (iv) processing and manufacturing water requirements are satisfied by utilizing rainwater in whatever form it is available.

4.1 Bangladesh

Field surveys in Bangladesh were carried out by the Intermediate Technology Development Group, a non-governmental organization (NGO). Survey teams were sent to each of the five ecological and water planning zones exist within Bangladesh (e.g., the North-Central, North-East, North-West, South-Central-West, and South-East zones). Information on the various technologies was obtained from literature surveys, field visits, questionnaire-based interviews, and focussed group discussions with agency officials and project beneficiaries. Rainwater harvesting was identified as the main, and perhaps only, freshwater augmentation technology being practised regularly in Bangladesh.

4.2 Nepal

Field surveys in Nepal were carried out by D&M Associates, a consulting company specialising in water, environment and sanitation issues in Nepal. Information on the various technologies was obtained from literature surveys, field visits, and interviews and discussions with agency officials and project beneficiaries. Five technologies for freshwater augmentation were identified as being in common use in Nepal; namely, the use of stone spouts and pokharis, spring development and protection measures, rainwater harvesting, bamboo-piped water supply systems, and hydraulic rams.

4.3 India

Field surveys in India were carried out by Prasad Modak and Associates of Bombay, a consulting organisation specialising in water and environmental issues. A literature survey, and interviews and discussions with concerned personnel, were used to prepare sixteen case studies of various freshwater augmentation technologies commonly used within India. The technologies identified included the adoption of industrial water conservation practices, use of reclaimed wastewater, recycling of process water, water harvesting for drinking water supply, traditional soil and water conservation practices, roof-top water harvesting, conjunctive use of surface and ground waters for irrigation, use of evaporation retardants, artificial recharge of groundwater, and use of water sprinkler and drip irrigation technologies.

4.4 Thailand

Field surveys in Thailand were conducted by the Water Experts Group of the Asian Institute of Technology, Bangkok, and by Dr. Sacha Sethputra of the Khon Khaen University. Technologies surveyed in Thailand includes rainwater harvesting for agriculture and domestic use, particularly in the northern and northeastern portions of Thailand, and desalination. A detailed case study of the Thai Rainwater Jar, which has become popular in the Indo-China region, was prepared.

5. Results of the survey

The results of the survey are presented below in Table 2 in summary form and in greater detail in Parts B and C. Technologies have been considered in four focal areas; water conservation, wastewater treatment and reuse, freshwater augmentation, and upgrading the water quality of natural waters.

Water conservation technologies include: water recycling in industries (i.e., cleaning wastewater for reuse in the same or other processes), dual distribution systems with drinking water in one system and water of marginal quality for non-potable uses in another, and mono-molecular organic surface films on the surfaces of water storage reservoirs to reduce evaporative losses.

TABLE 2. Summary Evaluation of Alternative Technologies for Freshwater Augmentation in Asia.

Technology	Extend of use	O&M	Level of involvement	Costs	Effectiveness	Suitability	Advantages	Disadvantages	Cultural Acceptability	Comments and Recommendations
Water recycling	Moderate. Only in the industrial sector	Moderate to high	Private sector. Government for legislation	High investment costs. Recurrent low	High	Industrial sector	Reduces freshwater needs, waste water amounts, and environmental hazards	High investment. Modifications to processes may be required	Highly acceptable	Has a high potential and should be encouraged. Often makes use of dual distribution systems
Dual distribution systems	Rare	Moderate	Household Government	Capital moderate. Recurrent low	Depends on quality and availability of alternative source	Where drinking water is scarce and marginal-quality water easily available	Reduces demand for drinkable water significantly	Costly. Can introduce aesthetic problems and health hazards	Low to Moderate	Limited potential in general. Should be encouraged in areas with high water scarcity
Mono-molecular organic surface films	Rare	Low	High involvement from Government	Moderate	Moderate, under research conditions low in practical application	Rural areas, especially in arid and semi-arid regions	Reduces water loss. Prevents mosquito breeding	Un-aesthetic. Loss of recreational value of the water body	Low	Suitability for large water surfaces unknown. Not recommended
Reuse irrigation water for irrigation	Moderate	Same as O&M for irrigation systems in general	Household, community, Government organizations	Same as for irrigation systems in general	High overall effectiveness	Not suitable in (arid) areas with salinity problems	Overall efficiency of water utilization increases	The quality of the drainage water may be low	Acceptable if the quality is OK	Promising potential. Further research required on economic techniques for extraction of salt and dilution processes
Sewage water in aquaculture	Moderate to high	Low to moderate	Household, community, government	Low	High	Suitable for the most common species of fish	Low operational costs. Effluent applicable for irrigation	Hygienic problems. Health hazards. Requires large areas of land	Acceptable in most Asian countries	Potential exists and increased use is recommended. Contamination with industrial waste should be avoided
Primary wastewater treatment	Low to moderate for farming. High as initial treatment	Low to moderate	Community	Low	High for irrigation, otherwise low	Rural areas	Low cost. Reduces requirements for further treatment	Aesthetic problems, pollution and health hazards	Acceptable in most areas	Recommended. Water quality monitoring required, when applied for irrigation
Secondary wastewater treatment	High	High	Community, private sector, government	High	High. The effluent will usually be non-polluting	Outside residential areas	Reduce hazards. Water may be reused in agriculture and industries	High costs	Acceptable	Recommended
Advanced wastewater treatment	Low	High	Community, private sector, government	Very high	High	Only when pollutants can not be removed by secondary treatment	Reduces environmental and health hazards	High costs	Acceptable	Recommended
Water treatment by lagoons and wetlands	Low	Low	Community, private sector, government	Low	Low to High, depending on chemical and physical characteristics, flow etc	Where suitable lagoons/wetlands are available	Reduces environmental and health hazards	High costs for land acqusition	Acceptable	Recommended only for organic wastewater after primary treatment. Research required on quantification of impacts
Rainwater harvesting	High	Low	Household, community, (government for promotion)	Low	High	No limitations	Simple technology, low costs, source close to user	Limited and uncertain supply, hygienic problems	High	Recommended
Fog and dew	Low	Low	Household, community	Low	Low	Few areas	Reduces the need for other sources	Low quantities	Acceptable	Low potential
Small scale water storage	Moderate	Low	Community, private sector, government	Low to moderate	Moderate to high	Rural areas, where suitable sites are available, preferably marginal lands	Augments water availability in dry season. Reduces (flash) flooding	Potential water quality problems. Requires land	Acceptable	Recommended
Artificial recharge of groundwater	Low	Low, except for deep well injections	Community, government	Moderate to high	Low to high, depending on hydro-geological conditions etc	In areas with appropriate geological and hydrological conditions	Augments dry season supply. Reduces flooding, land subsidence, sea water intrusion	High costs. compared to benefits. Risk of groundwater pollution	Acceptable	Potential exists. Further research required on the effectiveness under different geo-hydrological conditions
Artificial rain	Low	High	Government	High	Low	Areas with clouds but little rain	Can increase rainfall	Expensive The rain may fall outside the target area	Acceptable	Not recommended.
Desalinization	Low	High	Community, private sector	High	High	Coastal area with no other water source or with low-cost energy available	Reduces freshwater needs	High costs	Acceptable	Only recommended where no other source is available

Wastewater treatment and reuse technologies include: reuse of irrigation water by tapping return flows from the drainage system for further irrigation use downstream, the use of sewage effluent in aqua-culture (primarily the use of night soil and fecal-contaminated surface waters for fertilizing fish ponds, and irrigation), primary wastewater treatment (in which organic and inorganic materials are removed from waste water through sedimentation and filtering), secondary wastewater treatment (in which also the non-settleable solids are removed, primarily through biochemical processes, to promote the degradation of organic pollutants), advanced wastewater treatment such as carbon adsorption, microstraining, and desalination, and water treatment by lagoons and wetlands (as a form of secondary wastewater treatment utilizing the naturally occurring processes in these areas).

Freshwater augmentation technologies include: rainwater harvesting from roofs into jars and pots or small dams, fog and dew harvesting to condense air-borne moisture into liquid water for drinking water supplies or irrigation, small-scale water storage facilities including small ponds, tanks, surface reservoirs, and underground reservoirs formed by subsurface obstructions or dams, artificial groundwater recharge using infiltration from the surface or injection via deep wells, and cloud seeding.

Technologies for the upgrading of the quality of natural waters through desalinization include distillation, reverse osmosis and electrolyte systems.

5.1 Bangladesh

From time immemorial, rainwater has been playing a significant role in the socio-economic life of Bangladesh. In fact, the entire agro-economic fabric of the country is built on the particular rainfall pattern (commonly known as the monsoon) occurring ion the country. Nevertheless, very few studies have been carried out on rainwater harvesting. Those that are available are studies by Hossain and Ziauddin (1992), Sarker (1994), and Uttaran (1995). The major constraint on the development of rainwater harvesting technologies is a low education level of the people and the poor economic condition of their households. The past studies have provided few innovations for users in the methods of collection and storage of rainwater. A joint Department of Public Health Engineering (DPHE) and UNICEF programme, that has been working in the southern area of Bangladesh since 1984 to provide better quality drinking water, has been reported that, despite filtering, the water remained salty during the dry season and that people did not want to use it. Of the 90 DPHE-UNICEF sand-filtration facilities serving communities of 50 to 60 users, 45% were found to be idle.

In contrast, rainwater harvesting by the erection of bunds around farms is the most common and one of the earliest methods of rainwater harvesting in Bangladesh. In this method, earthen bunds with height of 30 to 45 cm and width of equal dimensions are constructed around the field. Farmers have learned from experience to match their cropping cycle with rainfall pattern. Rainwater meets around 78% to 97% of land preparation water requirement for aman crops. In saline areas, rainwater is used in the aman paddies to dilute saline river water until the river water becomes sweet. Over the entire aman crop cycle, rainwater meets around 50% of water requirements with the residual being obtained from river water sources.

Variations on this technology exist. In the upland areas of Bangladesh (NC zone- Jhenaighati, Nokla thanas) rainwater is stored in low lying plots usually in between two hills to be used in times of necessary. Plots are irrigated using traditional equipment such as dhoons and hicha. In the CW zone (Jhenaidah thana), rainwater is collected from surrounding lands at higher elevations and carded to storage ponds through a culvert. In saline areas (the Patuakhali, Khulna, Satkhira and Bagerhat districts), lands are located within polders or embankments erected to obstruct intrusion of saline water. In these areas, around three-quarters of the agricultural lands are being used for saline water-based shrimp culture delimiting options for freshwater based agriculture.

The polders also have the potential to revolutionize the drinking water supply systems in the saline areas (the greater Khulna, Satkhira, Patuakhali, Barisal and Noakhali districts) through the construction of "sweet water ponds" which are replenished by rainwater in the monsoon. In southern portion of Hatya and other remote islands in the Bay of Bengal, where there are very few tubewells, rainwater from these ponds is found to meet nearly 80% of the drinking water requirement in the monsoon season. In the saline area of the SW zone, rainwater meets 44% and 7% of drinking water requirement in monsoon and dry season, respectively. Ponds and tubewell water meet remaining 31% and 25% of monsoon season water drinking water requirement. Rainwater meets 49% of cooking water requirement in the monsoon season and is not used at all for bathing. On the other hand, in the NC zone, rainwater is not used for drinking purposes but, instead, is used for cooking (6%) and bathing/washing (11%). The bulk of the drinking, cooking and bathing/washing requirement is met from tubewells. In the NW zone, only 2% of the inhabitants reported using rainwater, for bathing only, as their entire requirement for drinking and cooking water is met from tubewells and, to some extent, from ponds/rivers and other surface waterbodies.

One of the oldest method of rainwater harvesting in Bangladesh is the use of roof-tops for collecting rainwater which is conveyed through a gutter to a pot, or motka, for immediate use or to a storage place for use later on. The water stored retains its colour and taste for around two months after monsoon, after which, the water gradually becomes contaminated with toads, mosquitos, cockroaches, etc. Previously, fish such as Koi, Singh or Magur (Anabas testudinews, Heteropreutes sp., and Clarias batrachus) were grown in the pots to eat the larvae of mosquitos and other insects. However, as these fishes discharge their own excreta in the water, which also degrades the quality of water, use of fish to maintain water quality is fast decreasing. Occasionally, alum or other locally made flocculant aid, like burnt shell, is used to purify the water. Water purifying tablets are very infrequently used.

Of the many industrial uses of harvested rainwater, one of the commonest is fish culture. In north Bengal and in Mymensingh, ponds are completely dried prior to the monsoon. The soil is enriched with lime and cow dung, and the water is treated with potash, to prepare the ponds for fish cultivation. In other areas, water is kept in the ponds at levels of 1 to 1.5 m prior to the monsoon. In saline areas like Hatiya, the same pond may be used for drinking water supply purposes. No soil treatments are applied to these ponds. In Sherpur District (Jhenaigati thana), rainwater is stored in embankments and used for fish culture. In the NC zone, excess water flowing out of the embankments passes through a net so that fish cannot escape from the pond.

5.2 India

The National Water Policy of India states that water is a prime natural resource, a basic human need and a precious national asset. It recommends that water resources planning be done for hydrological units, such as drainage basins or sub-basins. As far as possible, the projects should be planned and developed as multipurpose projects. Provision for drinking water should be given priority over other uses of water. The integrated and coordinated development of surface and ground waters and their conjunctive use should form an essential part of all water resources development projects, with recycling and re-use of water being an integral part of water resources development. Emphasis is placed on the preservation of the quality of the environment and ecological balance in planning, development and operation of water resources projects. The National Water Policy stresses the use of freshwater augmentation technologies as one means of alleviating India's chronic water shortages.

Water conservation may be achieved by modification of technologies and industrial processes in order to reduce the rate of water consumption. Better maintenance, interception and recovery of process water, and recycling can significantly contribute to water conservation efforts. Use of water of lesser quality, such as reclaimed wastewater, for cooling and as fire water can be an attractive option for large and complex industries to reduce their water costs, increase production and decrease the consumption of energy. This conserves better quality waters for potable uses. These technologies can be further complimented dew water harvesting or by constructing "dew ponds". The climatic conditions of some parts of Assam in Brahmaputra Valley and in hill areas hold promise for use of dew ponds. Public information programmes also contribute to water conservation in urban areas.

Agricultural water sources can be supplemented by small structures (pick ups) built across seasonal or perennial streams to check the flow of water at appropriate locations by constructing bunds using locally available materials like stones, boulders or even mud bunds turfed with a grass locally available (Maane hullu). Use of these structures results in water storage, groundwater recharge, prevention of soil erosion, and availability of water for other activities in areas where water would typically not be available for much of the year. In contrast, in the Krishna Delta, large demands for water from the Nagarjuna Sagar Reservoir have reduced the volume of freshwater reaching the Delta, and it has become necessary to utilize the groundwater supplies. In order to achieve an acceptable quality, however, groundwater must be used conjunctively with the limited surface water resources in a mix of 28:72, groundwater: surface water. Blending these waters should result in the conservation of storage in the reservoir of about 751 Mm³ for the first stage and 1 016 Mm³ for final stage, for a year with average inflows. In a more general sense, technological developments in the pumping methods and well construction have resulted in large-scale exploitation of groundwater throughout India which exceed the natural rate of replenishment of these resources. Thus, replenishment of the groundwater reservoirs by artificial recharge is essential.

TABLE 3. Water Evaporation Retardation (WER) Projects

States	Implemented for	Reservoirs/Lake	Surface area in acres	Year	Average Project period
Major Projects. Tamil Nadu	Madras Metro Water Supply	Cholavaram Red Hills	760 3200	1988-89	3 months
Andhra Pradesh	Hyd. Metro Water Works
	Division -I	Himayatsagar	1500	1986	4 months
	Division - II	Osman Sagar	1000	1987
	Division - IV	Manjira	3500	1988
Maharashtra	Irrigation Dept.	Chulbandh	300	1988	3 months
	Nagpur	Kolar	1000	1989
Gujarat	Govt. of Gujarat	Aji Dam	300 each	1986	6 months
		Fulzar		1987
		Sasoi		1988
		Nyari
		Bhadra
Rajasthan	PHED. Kankorli	Rajsamand	1200	1985	6 months
	PHED. Udaipur	Pichola	300	1986
		Fatehsagar	300	1987
	PHED. Bhilwara	Meja Dam	350	1988
	PHED. Jaipur	Ramgarh Lake	300	1989
	J.K. Inds. Ltd.	Rajsamand	1200
	Hind Zinc Ltd.	Udsisagar	300
		Tidi Dam	350
	Lakshmi Cement		300
Other Project Sites
	PHED. Dhar	Dhar Res.		1988	2 months
M.P.	PHED. Seoni	Seoni Res.
	Gwalior Rayons	Noda Res.
Rajasthan	PHED. Ajmer	Foy Sagar		1986
	PHED. Sirohi	Sirohi Res.		1986	3 months
	PHED. -	Dungarpur Res.		1988
	PHED. Pali	Pali Res.

In many parts of the country, which have to face the vagaries of the monsoon, dependance on groundwater has increased tremendously, particularly in those areas where surface water resources are either lacking or inadequate, and storage of surface water is uneconomical because of high evaporative losses. Water loss due to evaporation has led to serious problems including acute shortages of drinking water for human consumption in some parts of India. Considering the huge loss of precious water, use of Water Evaporation Retardants (WER) on open surfaces of lakes and reservoirs is now being promoted by various State Governments and Local Authorities. Various substances capable of forming mono-molecular layers on a water surface have been investigated, and fatty alcohols in their pure form were found to be most suitable and effective in retarding evaporation with no known side effects. Water savings resulting from the prevention of evaporative losses using cetyl and stearyl alcohol have been reported to be as high as 50%, but are generally between 20% and 40%. Table 3 shows a list of projects where the evaporation retardants have been used.

In India, rainfall is confined to about four months in a year and is inconsistent both in space and time, causing severe drought. In this context, whatever the source water used, irrigation is a must for agriculture in the country. However, there is an urgent need for efficient use of present available water so as to irrigate the maximum possible gross cropped area. In India, sprinkler irrigation is being adopted in hilly terrains, for irrigation of many plantation crops. The use of sprinkler systems, which mimic natural rainfalls, was introduced in the State of Hariyana in 1970, and other states like Rajasthan, Uttar Pradesh, Karnataka, Gujarat, Maharashtra have since implemented sprinkler irrigation systems. In the State of Hariyana, it has been found that, the use of sprinkler irrigation has saved about 56% of water for the winter crops of Bajra and Jawar, while for cotton it has saved 29% as compared to the traditional gravity irrigation. Drip irrigation systems, a variation on piped irrigation that delivers water directly to the root zone of the crops, are of very recent origin, and are used on a limited scale in Tamil Nadu, Karnataka, Kerala and Maharashtra mainly for irrigation of coconuts, coffee, grapes and vegetables. Experimental studies on sugarcanes, banana and other fruits have shown a very high profitability in addition to water conservation.

TABLE 4. Water Loss Under Various Irrigation Methods.

	Temperate Climate	Hot Climate
Surface Irrigation	30 - 45%	35 - 50%
Gate pipe Irrigation	15-20%	20 - 25%
Sprinkler Irrigation	6-9%	10 - 20%

5.3 Nepal

Although Nepal has one of the world's largest per capita water resources, most of the population does not have easy access to safe drinking water and, at times, there are acute shortages of water for all economic purposes. Urban settlements are mostly affected by the shortage of water whereas, in the rural areas, the problem is linked to lack of accessibility of water. The main sources of water in the country are rivers and springs in the hilly regions, and shallow and deep groundwaters in the Terai. Due to the shortage of water from the municipal supplies in the urban settlements, primarily in the Kathmandu Valley, there is a trend toward illegal extraction of underground water using shallow and deep wells, thereby lowering the water table and leading to the possibility of land subsidence and foreseeable tectonic effects. Associated problems are the decline in the yield and productivity of wells and the increasing incremental cost of lifting water from ever-increasing depths. For these reasons, Nepal has identified freshwater augmentation technologies to protect both water quantity and water quality to the extent possible.

Alternative technologies include the use of traditional technologies such as stone spouts and Pokharis, which were the only sources of water in the Kathmandu Valley in the past. However, there is a need to conserve and restore the ponds, aquifers, wells and stone spouts which have been neglected. Conservation and restoration of stone spouts and Pokharis is related to spring development and protection. Spring protection technologies are widely used in the central and eastern hills of Nepal. These are simple and ideal technologies for use where yield of the source is very low and water is drawn at the source itself. Likewise, rainwater harvesting has been popular where there are neither springs nor streams nearby to fulfill the water demand of the community.

Various distribution systems have also been developed in Nepal based upon traditional technologies. For example, bamboo piped water supply systems are not very common, but may prove an ideal system for remote areas where GI and HDPE pipes and fittings are not available and only bamboo is easily available and cheap. Use is also being made of hydraulic rams to pump water using the hydraulic power of the water itself, thus eliminating the need for diesel or electrical power to drive water pumps. The principle advantages of this system are its simplicity and lack of an energy cost in the operation of the system. This system is suitable in places where there is plenty of water, and the area to be supplied is situated at a lower level than the source area.

5.4 Thailand

Freshwater augmentation is practised in Thailand for three main purposes; namely, for agricultural, industrial, and domestic uses. The status of freshwater augmentation technologies in Thailand is summarized in Table 5. The two most common and successful technologies are recycling of harvested rainwater in irrigation systems and rainwater harvesting for domestic rural water supply purposes. Technologies that are related to domestic rural water supply are shown in Table 6. Important issues related to the technologies are also summarized.

TABLE 5. Status of Freshwater Augmentation Technologies in Thailand.

APPROACH	RAIN-FED SYSTEMS	MODERN SYSTEMS	TRADITIONAL SYSTEMS	INLAND FISHERY	INDUSTRY	RURAL
Recycling to maximize the use of existing resources	Planting suitable crops (e.g., deep rooted beans) Planting cover crops	Well-known engineering techniques	Recycling among several small systems	Bottom dwelling fishes used to clean fish ponds	Well-known, engineering techniques	Experimental desalination
Systems to augment existing sources	Traditional contour bunding	None known	Traditional bamboo or earthen weirs found throughout SE Asia		None known	Several facilities used (See the following Table).

6. Recommendations of the workshop

The participants in the Workshop:

· Felt that the source book would be of immense value to policy makers and practitioners in the field, realizing the depletion of water resources now and in the years to come.

· Suggested that the source book should highlight the sensitivity and limitations of the technologies mentioned. Recommended that the cost of the technologies should differentiate the capital and operation and maintenance costs.

· Recommended that the source book be disseminated to existing networks on water, health, and the environment (e.g., ENSICNET, CEHANET, INFORTERRA, etc.) rather than through new networks.

· Recommended that the source book have a specific section on water quality and a discussion of water quality issues related to the various technologies for fresh water augmentation in the Introduction.

· Agreed to recommend that every country introduce and adopt a Ground Water Act if one does not already exist.

TABLE 6. Summary of Freshwater Technologies and Related Issues.

TECHNOLOGY	SOURCE WATER/USE	EXTENT OF USE	EFFECTIVENESS	CAPITAL COST	OPERATING COST	MAINTENANCE COST	SKILLS REQUIRED	EQUIPMENT REQUIRED
RAINWATER JARS	Rainwater/domestic use	Extensive	Very high	$16/m3	0	$6/m3/year	Minimal	Small construction equipment
RAINWATER TANKS	Rainwater/domestic use	Less extensive	Medium	$24/m3	0	$8/m3/year	Minimal	Small construction equipment
SHALLOW WELLS	Groundwater/domestic use	Extensive but declining	High	$120/well	0	0	Minimal	Manual tools for digging and concrete work
IMPACT WELLS WITH HANDPUMPS	Groundwater/domestic use	Sporadic	Low	$200/well	0	0	Minimal	Homemade digging equipment and handpump
DEEP WELLS WITH HANDPUMPS	Groundwater/domestic use	Extensive	High	$16000/well	0	$80/year	Minimal	Drilling rig, piping and handpump
DEEP WELLS WITH ELEC. PUMPS	Groundwater/domestic use	Extensive, upgrade of Impact Wells	High	$2 400/well	up to $200/year	$80/year	Minimal	Drilling rig, piping, electric pump and accessories
PONDS	Rainwater/domestic use	Sporadic	Low	$3/m3 of earth moved	0	$20/year	Minimal	Traditional tools for earthwork
SPRINGS	Groundwater/domestic use	Sporadic	Low	$4 000/km of pipe	$1 000/year	$200/year	Medium	Tools for concrete work and piping
PIPED WATER, VILLAGE SUPPLY	Groundwater/domestic use	Extensive, upgrade of Deep Wells	High	$12 000 to $56 000/system	$1 000/year	$1 000/year	Medium	Tools for concrete work, piping, pumps, tanks, valves and other accessories
WEIRS	Streamflow/domestic and agricultural use	Extensive	High	$12 000/unit	$80/year	$80/year	Medium	Tools for wood and concrete work and some earthwork
SMALL RESERVOIRS	Streamflow/domestic and agricultural use	Extensive, but few sites remain	Low	$160 000/unit	$960/year	$80/year	Medium	Tools for woodwork, bamboo, gravel and stone

7. Information sources

BBS 1993. Statistical Year Book of Bangladesh, 1993, Government Printer, Dacca.

Department of Health s.d. Manual for Caretakers of Village Pipe Water Supply Systems (Medium and Small Sizes), Rural Water Supply Division, Department of Health, Bangkok 2535. Department of Health s.d. Manual for Caretakers of Village Pipe Water Supply Systems, Rural Water Supply Division, Department of Health, Bangkok 2535.

Hossain, M.D. and Ziauddin, A.T.M. 1992. Rainwater Harvesting and Storage Techniques from Bangladesh, Waterlines, January 1992.

NESDB 1992. Manual for Preparation of Master Plan for Provision of Drinking and Domestic Water for Villages in Each Province, NESDB.

NESDB 1992. Status of Drinking and Domestic Water in Rural Areas, NESDB Division of Rural Development Coordination.

Office of Public Health s.d. Manual for Management of Village Pipe Water Supply Systems, Sanitary and Environmental Health Division, Office of Public Health, Chiangrai 2535.

Thongtip, S., Pacharin, L., and Wichien, K. 1995. Esan Women and Water Management, Research and Development Institute, Khon Kaen University (in That).

Water Resources and Environment Institute 1986. Manual of Weir Construction, Khon Kaen University, Thailand (in Thai, English, Laos and Cambodian).

Water Resources and Environment Institute 1991. Small Scale Water Resources: Clean Water and Sanitation, Khon Kaen University, Thailand (in Thai).

Water Resources and Environment Institute 1991. Manual of Small Weir Design, Khon Kaen University, Thailand.

Water Resources and Environment Institute 1991. Manual for Construction of Farm Ponds, Khon Kaen University, Thailand.

Water Resources and Environment Institute 1991. Manual for Construction of Impact Wells, Khon Kaen University, Thailand.

(introduction...)

Water conservation technologies cover all methods of conserving water through increasing water use efficiency, enhancing capacity to retain runoff water, and eliminating water pollution. Water use efficiency largely depends on availability and adoption of water saving devices and willingness of the consumers to reduce their total water consumption volumes. Furthermore, existing rules and regulations such as pricing mechanisms, reduce the total volume used, while economic incentives largely affect the choice and adoption of technology for water conservation technologies.

Water conservation processes can broadly be categorized into pre consumer and post consumer based approaches. Pre consumer based approaches involve increasing the efficiency of water extraction, storage and conveyance. Usually a large amount of water is lost either through evapotranspiration or seepage during transfer from the abstraction point to the point of use. It is estimated that, of the total rainfall in Thailand, about 70% returns to the atmosphere through the process of evaporation and transpiration (AIT, 1982). Using technologies that can minimize losses such as reducing evaporative losses from reservoirs, seepage losses from canals and water application losses prior to the water being used for economic purposes, can conserve a vast amount of water. In contrast, post consumer based approaches include the use of marginal quality waters, such as slightly saline water from the sea, untreated groundwater from shallow tubewells and rainwater collected from thatched roofs, for washing, toilet flushing purposes, etc.

In Asia, the agricultural sector consumes more than 75% of the total water withdrawn from all sources. About 60% of this water is lost during conveyance and distribution. Engineering technologies to reduce these losses, and to enhance utilization of water in irrigation schemes, are well studied and established practices which are beyond the scope of this book. In contrast, agronomic technologies such as efficient and modem methods of irrigation (including drip irrigation, sprinkler irrigation and surge irrigation) are less well-known and may be considered water conservation technologies. These technologies are documented in standard textbooks on agricultural and water resources engineering, and are briefly reviewed herein.

Recycling is also an alternative, post consumer technology for conserving and augmenting water supplies. It involves the reuse of water previously used for one purpose for a particular use in another application, before it reaches a natural waterway or aquifer. By using water several times, farms, urban areas and industries can increase the productivity of each litre of water consumed. Industries can conserve water by changing production processes from open to closed systems. In many industrial plants it is possible to recycle the cooling water. Some industries process water several times, and treat it at the end of its period of usefulness, prior to discharging the water to a natural water course. Reuse conserves raw water and, at the same time, reduces the volume of wastewater as well as wastewater treatment costs substantially. Several case studies on water conservation practices in India are described in Part C of this Source Book. In terms of particular technologies, there are no specific technologies involved, but rather a way of managing conservation practices in individual households and industries. Some of the technologies typically being practised in the Asian Region also are presented herein.

1.1 Dual water distribution system

Technical description

Water reuse, and the reuse of wastewater in particular, is receiving increasingly wide attention, even though it is often considered to be of marginal quality. Use of treated wastewater through dual water distribution and plumbing systems can provide a secondary source of water for purposes such as irrigating private gardens and toilet flushing. The provision of waters of lesser quality through a separate distribution system for non-potable purposes from alternative sources of supply can help lower the demand for potable freshwater. Application of this technology is largely a matter of cost, acceptance and practice, as the distribution technology involved is not significantly different in dual distribution systems compared to conventional single distribution systems.

In the Kathmandu Valley, where water scarcity is increasing, conjunctive use of shallow groundwater sources for toilet flushing and washing of clothes, together with potable water supplied through the municipal water supply system for other purposes, is being practised in residential areas. A rower pump (hand pump) is fitted to a 3.8 cm diameter polyvinylchloride pipe ranging from 6 m to 15 m in length which is driven to the ground. Water from the groundwater source thus tapped is pumped manually whenever needed.

Extent of Use

This technology is widely used in the Kathmandu Valley in locations where the groundwater table is within 15 m of the ground surface. It is also popular in locations where the municipal water supply is intermittent. People of low income are increasingly using this technology in preference to the higher cost municipal supply.

Operation and Maintenance

The operation and maintenance of dual distribution systems is simple, and involves keeping the pipe and the pump clean. Maintenance consists of changing the pump washer once a year or whenever it starts leaking. No additional maintenance of the municipal supply system is required, and no changes in municipal distribution system operation are necessary.

Level of Involvement

Providing dual distribution systems at the household level requires no external involvement relative to the groundwater sourced portion of the system. The municipal sourced portion of the system is generally constructed and operated by the local governmental unit.

Costs

The total cost of the groundwater sourced portion of the system is about $55 for a 10 m deep well.

Effectiveness of the Technology

This technology has helped alleviate the problem of water scarcity in Kathmandu. For an average household, more than 60% of the annual household water requirements is met by using shallow groundwater, which is of lower quality than the municipal water, for non potable purposes.

Suitability

Water supplied from the rower pump can be used for toilets, bathing, gardening, car washing, and similar purposes. The dual distribution system is most suitable for use in areas where the groundwater is within 15 m of the ground surface; otherwise, a mechanical pump will be necessary, adding to the cost of the groundwater sourced portion of the system.

Advantages

This technology is inexpensive and can be constructed using locally-available technology. Water is made available whenever needed, and use of the dual sourced system eases the water scarcity problem not only at the household level but also throughout the entire city.

Disadvantages

Conjunctive use of dual sourced water may be limited as a result of poor water quality. Water drawn from alternative sources may not be used for drinking even after boiling because of odours and tastes associated with groundwater. Further, such water may pose severe health hazards if the abstraction point is located too close to septic tank outflows. The possible high nitrate concentrations and bacterial levels that may be present in surfacial groundwaters may also lead to health hazards when used by poor people and children for drinking purposes. Widespread use may contribute to a decline in the groundwater table (due to over exploitation). Also, water logging and mosquito breeding in the pump area may occur if proper drainage is not provided.

Cultural Acceptability

No cultural problems have been noted, although use may be limited due to odours associated with the groundwater.

Further Development of the Technology

This technology will be more attractive and useful if simple and inexpensive electric motors are attached to the tubewell and the groundwater sourced portion of the system is fully incorporated into the household water supply system.

Information Sources

Dirgha Nidhi Tiwari, Koteswar, c/o Post Office Box EPC 4000, Kathmandu, Nepal. Tel. 977 1 410249, E-mail: [email protected].

1.2 Evaporation reduction

Technical Description

Evaporative losses can be controlled using various technologies. For example, the use of mono molecular organic surface films has been shown to be an efficient technology for reducing such losses. The mono molecular film is applied to an open surface water storage area and allowed to over the water surface. Typical mono molecular films are comprised of long-chain fatty alcohols such as cetyl alcohol (hexadecanol) and stearyl alcohol (octadecanol). These chemical not only suppress evaporation but also prevent mosquito breeding in the water. The use of stearyl alcohol in doses of up to 70 g/cm² can reduce evaporative losses by up to 55% of the loss due to evaporation from a free water surface. However, the economics and extent of use of this technology are yet to be explored and established.

Extent of Use

Use of surface films to reduce evaporative losses is principally in arid and semi-arid regions.

Operation and Maintenance

The operation and maintenance requirements of this technology are negligible. Maintenance is required only for the rafts and boats, which may be locally constructed, used during the application of the evaporation retardants. No specialized skill is required.

Level of Involvement

The implementation of this technology is generally carried out by government departments, primarily the public health engineering and water supply departments. In India, it is now being promoted by various state government agencies and local authorities. Generally, control of evaporation is focused at the government level having prime responsibility for water resources management.

Water Evaporation Retardants In India, the use of Water Evaporation Retardants (WER) is being investigated as a water conservation measure in surface waters. Control of evaporative losses is being effected using Ceto-Stearyl alcohol, a blend of saturated fatty alcohols, previously imported at high cost and not readily available in India. India's first fatty alcohol plant was commissioned in 1981 at Jalgaon, Maharashtra, by Aegis Chemical Industries L-td,, using an exclusive technology based on an high pressure hydrogenation technology developed in collaboration with Haldor Topsoe, Denmark. The plant is one of the few in the world and the only one in India, producing alcohols to international specifications. In 1983, Aegis successfully developed an effective water evaporation retardant, Acilol TA 1618 WER, an emulsion based on fatty alcohols manufactured from natural vegetable oils. Acilol TA 16118 WER was developed in the laboratory after extensive research aimed at identifying a product compatible with the climatic conditions of the country. Field trials were conducted in March 1984 with the help of Gujarat Engineering Research Institute. These trials confirmed the effectiveness of Acilol TA 1618 WER. A dispensing technique for applying Acilol TA 1618 WER to water surfaces, consisting of barrel tanks with a drip feed arrangement mounted on "Floating Rafts" anchored at different points on the lakes or reservoirs, was also developed to suit Indian conditions. The first major project using this technique to conserve water was undertaken by the Public Health Engineering Department (PHED), Jaipur, at Ramgarh Lake in April, 1985. About 50 mg/m2/d of the chemical is required arid can result in a savings of about 30% of the daily loss of water due to evaporation.

Costs

No cost data were available as this technology remains largely experimental.

Effectiveness of the Technology

Of the various substances capable of forming mono molecular layers on a water surface, fatty alcohols in their pure form have been found to be most suitable and effective in retarding evaporation with no side effects (AIT, 1982). Savings from the prevention of water loss due to evaporation have been reported to be as high as 0.70 million cubic metres of water (equivalent to one month's water supply for Jaipur City, India) using Cetyl and Stearyl Alcohol as an evaporation retardant.

Suitability

The technology is most suitable in small surface water storages where there are no strong winds to disrupt the retardant layer.

Advantages

Use of evaporation control techniques requires a small capital investment. Locally constructed rafts can be used in its application, and skilled labour is not required, except for operation of motorized boats. Fatty alcohols present no hazards in handling, and are non-inflammable, non-toxic, and non-irritating. There are no known harmful effects, making this technology safe for application on drinking water lakes and reservoirs. There are also no known ecological ramifications, as the alcohols contain straight chain carbon compounds which are biodegradable and permeable to oxygen.

Disadvantages

The fatty alcohols used as WERs are not readily available and are costly. Historically, fatty alcohols were produced only by sperm whales or by sodium reduction of animal oils and fats. It was only after the development of high pressure hydrogenation process that good quality fatty alcohols are now commercially available. However, this is a very advanced technology, and requires trained and skilled staff to operate.

Cultural Acceptability

There are no known problems with cultural acceptability.

Further Development of the Technology

More research is necessary in the area of stabilising the chemical film in the face of high wind velocities. Properties such as rate of spreading, specific resistance to evaporation and surface viscosity are required to be measured in evaluating the efficiency of the retardant.

Information Sources

Contacts

Asian Institute of Technology,
Water Engineering and Management Program,
Post Office Box 2754, Bangkok, Thailand.
Tel. 00 662 516 0110,
Fax: 00 662 516 2126,
E-mail: [email protected].

Bibliography

A.C. Desai, T.K. lyer, and V.M. Tople 1990. Use of Water Evaporation Retardants for Water Conservation, Journal of Indian Water Works Association, April-June, 193-194.

Asian Institute of Technology (AIT) 1982. Evaporation Control Using Monomolecular Organic Surface Films. AIT Research Report No. 1982-2, Division of Water Resources Engineering, AIT, Bangkok.

1.3 Coconut pick-ups

Technical Description

In South India, coconut pick-ups is a name popularly used for weirs constructed exclusively to provide water to coconut gardens. These weirs or pick-ups are small structures built across the seasonal or perennial streams to slow the flow of water at an appropriate location. This results in surface water storage, groundwater recharge, reduction of soil erosion and availability of water for other purposes. The bunds that form the puck-ips are constructed of locally available materials such as stones, boulders or mud turfed with grass. The bunds are usually built within the water course almost to the height of the surrounding ground level, depending upon the width and steepness of the stream. When stream flows occur, the coconut plantation, situated within the floodplain on either side of the water course, is temporarily flooded. The water impounded by the structures recedes within 3 to 4 days, with the excess water frequently diverted into a tank or cistern. Sometimes there will be several coconut pick-ups within a catchment, and several tanks which may flow from one tank to the other.

Extent of Use

This technology has been used in many places in South India.

Operation and Maintenance

The pick-up is constructed by the farmers and hence both operation and maintenance is the responsibility of the user. The principle maintenance requirement is keeping the pick-up sealed to prevent loss due to leakage.

Level of Involvement

Usually, the pick-ups are managed by the users who build them. Repair and maintenance are also carried out by the user. Government may be involved in the funding of the pick-ups, and in the initial permitting of the project site. This function is commonly performed by the local self-governing body that functions as a farmers/users association and manage their activities.

Costs

Construction of a typical coconut pick-up for an area of 10 ha in India would cost about $2 000.

Effectiveness of the Technology

The technology is successful in providing adequate water to many coconut farmers for agricultural purposes.

Suitability

The technology is suitable for use in tropical areas with moderately rolling topography and small streams.

Advantages

The use of pick-ups encourages groundwater recharge by promoting infiltration and vertical percolation. This recharge helps to sustain yields to percolation tanks and tube wells supplying open tanks. The recharge of open wells is almost immediate, even at a distance of up to 0.5 km depending on soil structure and gradients.

Ponds created by the pick-ups can serve also as a drinking water source for livestock from up to 10 villages.

Further, the floodwaters deposit a few millimetres of silt behind the pick-up structure and enrich the soils of the floodplains behind the pick-up with nutrients associated with materials like manure, leaves and other terrestrial debris carried in the runoff flows. These minerals and nutrients enrich the soil particularly during the monsoon season without the use of fertilizer supplements.

Disadvantages

The presence of the temporary ponds behind the pick-ups can promote mosquito growth and exacerbate human health risks.

Cultural Acceptability

Being a traditional technology, the use of pick-ups is culturally acceptable. Some religious functions are held in the pick-up areas.

Further Development of the Technology

More realistic predictions of sustainable water yields will be needed to design cost effective and adequately-sized bunds.

Information Sources

Abdel-Rahman, H.A. and I.M. Abdel-Magid 1993. Water conservation in Oman. Water International,. 18 (2): 95-102.

Asian Development Bank (ADB) 1993. Water Utilities Data Book: Asian and Pacific Region. ADB, Manila.

Asian Institute of Technology (AIT) 1982. Evaporation Control Using Monomelecular Organic Surface Films, AIT Research Report No. 1982-2. Division of Water Resources Engineering, ATT, Bangkok.

Bhatia, R., P. Rogers, J. Briscoe, B. Sinha, and R. Cestti 1994. Water Conservation and Pollution Control in Indian Industries: How to Use Water Tariffs, Pollution Charges and Fiscal Incentives. UNDP-World Bank, New York.

Frederick, K.D. 1992. Balancing Water Demand with Supplies, The Role of Management in a World of Increasing Scarcity. World Bank Technical Paper No. 189. The World Bank, Washington, DC.

Gracy, C.P., B.L. Chinanda, C.K. Jalajakshi, and K.H. Vedini 1995 Traditional Methods of Soil and Water Conservation - A Case of Coconut Pickups. In: Proceedings of the National Workshop on Traditional Water Management for Tanks and Ponds. Centre of Water Resources and Ocean Management, Anna University, Madras.

Sasekumar, A, N. Marshall, and D.J. Macintosh, Eds 1994. Integrated Planning and Management of Freshwater Habitats, including Wetlands. In: Ecology and Conservation of Southeast Asian Marine and Freshwater Environments including Wetlands. Kuala Lumpur, Malaysia, pp. 311-322.

Vigneswaran, S., et al. 1989. Low Waste Technologies in Selected Industries. Environmental Sanitation Reviews No. 27, Environmental Sanitation Information Centre, Asian Institute of Technology, Bangkok.

2.1 Sewage reclamation using conventional wastewater treatment

Technical description

In India, treated municipal sewage is being used by industry for cooling water and in firefighting. The Hindustan Petroleum Company Limited (HPCL), located in Bombay, has used seawater for these purposes, but is in the process of converting to the use of reclaimed water (see the Indian Case Studies in Part C of this Source Book). The use of reclaimed water better meets the pollution control regulations established by the Central Pollution Control Board's MINAS (Minimal National Standard) regulations, and minimizes the operation and maintenance problems inherent in the use of the seawater for cooling and firefighting purposes. Use of reclaimed sewage also enables the refinery to reduce the number of blow downs from the cooling towers and thereby reduce the volume of cooling water effluent required to be treated to MINAS.

The components of the sewage reclamation, treatment and reuse process are a sewage pump housed in a dry well for easy access, a rising main to convey wastewater from the pump house to the factory premises, a water reclamation plant within the factory, a storage reservoir for the reclaimed water, and a distribution system to channel the reclaimed water to the cooling towers. A wet well is likely to be required to retain the incoming sewage from the sewer and balance flows to the treatment plant, and a mechanical screen should be installed in the system upstream of the pump to remove particulates prior to the wastewater entering the pump house.

The reclamation plant typically consists of a flash mixer for mixing of chemicals with the incoming wastewater. An alum solution, used to flocculate particulates that have passed through the mechanical screen, is dosed in a chamber upstream of the flash mixer. Following dosing. The wastewater passes through a clari-flocculator to remove fine suspended matter and colloidal turbidity. The resultant clear liquid flows over a weir and is collected in the launder. The resultant sludge is collected in the bottom of the clarifier tanks and discharged via the excess sludge sump. The clarified wastewater is then filtered through a rapid sand filtration unit, using a layer of quartz sand and a layer of graded gravel, and separated into two streams. One stream is passed through an ion-exchange softener unit, prior to being recombined with effluent stream in proportions calculated to produce the desired degree of hardness. The blended, reclaimed water is then chlorinated using a vacuum type chlorinator.

Extent of Use

This technology can be used in industries where a large volume of cooling water is required and an adequate source of wastewater is readily available.

Operation and Maintenance

Maintenance is related to the operation of the water reclamation plant and pumping system. Operations are generally conducted over a 24 hour period, requiring adequate trained human resources in at least three shifts to operate the treatment plant.

Level of Involvement

This technology may be implemented at the individual industry level or incorporated into a local government wastewater treatment scheme.

Costs

The total capital cost of a 15 million litre per day (MLD) reclamation system is about $ 4 million. The annual operation and maintenance costs are about $410 000, or about $ 0.02 per m³.

Effectiveness of the Technology

Use of reclaimed water is expected to reduce the cooling makeup water requirement from 4 500 m3/hr (or 108 000 m3/day) to about 625 m3/hr (or 15 000 m3/day).

Suitability

This technology is suitable where large quantities of wastewater are available nearby. Advantages

Use of this technology reduces the problem of high TDS in the cooling water which occurs when sea water is used as cooling water. Where municipal water is used for cooling purposes, use of reclaimed wastewater also results in a net savings in the drinking water supply of a municipality since industrial demands on this source are reduced.

Disadvantages

Domestic wastewater is best suited for reclamation as industrial wastes may contain contaminants that make such wastes unsuitable for reclamation. This technology has an high capital cost, especially if the sewage line is far away from the industry, and may have relatively high operation and maintenance costs, depending on the reclamation technology used.

Cultural Acceptability

No problems have been noted since the reclaimed water is not for human consumption.

Further Development of the Technology

The technology is readily transferable and can be used by other industries. New industries should consider the use of reclaimed water in their overall plan, which will make it cost effective to implement.

Information Sources

AIC Watson,
The Sewage Renovation Project at Hindustan Petroleum Corporation Limited (HPCL), Bombay, India. AIC Watson.

2.2 Sewage reclamation using reverse osmosis

Technical description

Industries in growing metropolitan areas may face production losses as a result of excess demand for municipal water. Madras Fertilizers Limited (MFL), Madras City, Tamil Nadu, India, has faced such a situation in 1983 and 1987 (see the Indian Case Study in Part C of this Source Book). As a result, MFL has explored alternatives including the use of desalinated sea water and treated wastewater to supply process and cooling water to its operations. After detailed review of these alternatives, the Company decided to reclaim water from city sewage using advanced waste water treatment followed by Reverse Osmosis (RO) as an additional purification step. The Company has a daily water requirement of 20.25 MLD, 68% of which is required for cooling purposes.

Wastewater used by the plant is treated to tertiary standards using an activated sludge process, with the treated water being further reclaimed through excess lime addition, ammonia stripping, recarbonation, chlorination, multimedia filtration, activated carbon filtration, cartridge filtration, and reverse osmosis using thin film polyamide membrane.

Ammonia stripping is carried out in first-stage and second-stage counter current flow ammonia strippers, which are similar to cooling tower cells. Treated wastewater is sprayed from the top while air is sucked in from the bottom of the tower by an induced draft (ID) fan located at top of the tower. Free ammonia is blown out of water into the air. The ammonia-stripped water is pumped to a first stage carbonation tower and calcium carbonate clarifier, where the pH is brought drown to 7.0, and chlorinated before being sent to storage. The excess sludge from the clarifier is disposed of in sludge beds, and water drained from sludge is recirculated into the inlet lagoon.

Although most undesirable constituents like BOD, hardness, and ammonia are removed by tertiary treatment, the total dissolved solids (TDS) content is generally higher than well water. This would increase overall water consumption by making it necessary to add make up water regularly to dilute the salinity, increase the corrosiveness of the recirculating water, and increase chemical dosing needed to keep corrosion and sealing problems in check; all of which result in increased operating costs. To reduce these undesirable salinity-related costs, MFL selected Reverse Osmosis (RO) treatment of the treated effluent as a convenient and viable method.

Extent of Use

Industries requiring large volumes of cooling water could use this technology.

Operation and Maintenance

A qualified chemical engineer is required to supervise the treatment process. Other operation and maintenance requirements include the maintenance of the physical facilities, routine monitoring of the plant operation, and oversight of the supply and circulation system.

Level of Involvement

This technology is typically implemented at the individual industry level.

Costs

The total capital cost of a 20 MLD reclamation and reuse facility is estimated to be about $ 18 million. Annual operation and maintenance costs are about 10% of the capital cost.

Effectiveness of the Technology

Reclaiming sewage releases an equivalent amount of potable water in the municipal water system for domestic and other uses in the city.

Suitability

This technology is suitable for use in areas where a large quantity of sewage water is available nearby.

Advantages

Use of reverse osmosis proved to be a less expensive alternative than other alternatives such as sea water desalination, and resulted in a savings in the drinking water supply.

Disadvantages

The initial capital cost of an RO system may be high, especially if the sewerage line is far away from the industry. This system is also expensive to operate due to high power consumption requirements.

Cultural Acceptability

No problems are known as the reclaimed water is not for human consumption,

Further Development of the Technology

The technology is transferable and can be used by other industries. New industries should consider integrating this technology into their overall plant design to make it cost effective.

Information Sources

Rajappa, M.S. 1990. Reclaimed City Sewage as Industrial Water. Journal of Indian Water Works Association, Jan-March, 95-100,

2.3 Wastewater treatment using wetlands

Technical description

Untreated wastewater is usually discharged into nearby streams or water courses. It is generally assumed that the waste assimilative capacities of these natural water sources are high and can be sustained in the long term. However, as the negative effects of this waste disposal philosophy are increasing, low cost and low energy alternative systems, such as utilization of nearby wetlands, is usually indicated. Wetlands which lie in the buffer zone between the municipal areas, agricultural fields and the water courses provide a sound means for filtering wastewater before it is discharged into a river or other surface water feature. In the past, natural wetlands have been used as natural nutrient sinks for the treatment of wastewater.

Wetlands act as natural purification systems. Their hydrological regimes, sediments, and biotic components enhance the ability of wetlands to process wastewaters. Hydrological regimes are influenced by precipitation, surface water inflows, groundwater inflows, evapotranspiration, surface water outflows, groundwater outflows and changes in the water storage capacity of the system. Wetland sediments accrete carbon through decomposition of organic matter. This may result in very low oxygen concentrations within sediments. The systems exhibit very high primary production rates with the resulting organic soils having low bulk densities, high water holding capacities, low hydraulic conductivities, high organic matter contents, and extremely high caution exchange capacities (Eassan et al., 1988), retaining most of particulate organic matter produced in the wetland. Biotic components include plants, phytoplankton, invertebrates and vertebrates.

Operation and Maintenance

Operation and maintenance requirements depend on the type of the reclamation system. Pumps require monitoring and a preventive maintenance system, which requires skilled personnel, especially if there are several pumps within the system. Periodic inspections and ecological monitoring are required to ensure the quality of the output water, and to maintain the wetland vegetation.

Level of Involvement

This technology may be implemented by government agencies and communities.

Costs

The capital costs of constructing and managing a wetland treatment system vary widely according to specific local conditions. In augmented natural wetland systems, the capital costs consist solely of the cost of pipes and pumps. In constructed wetlands, land acquisition and development costs are also incurred. Easson et al. (1988), citing Tuchobanoglous and Culp (1980), provide a general guideline to the capital costs of wetland wastewater treatment, in 1980 dollars, as shown in Table 7. Costs of wetland treatment could be lower in Asia. The per unit cost of wetland treatment of wastewater, as provided by Easson et al. (1988) citing Fritz and Helle (1979), was one-half of that of a conventional treatment system. The operation and maintenance costs are also comparatively low, as wetland treatment systems require only periodic inspection and ecological monitoring. Nevertheless, the environmental investigations needed to identify the linkages between ecosystem components in the case of augmented natural wetland systems may increase the cost of implementing this technology significantly.

TABLE 7. Cost of Wetland Treatment Systems

Costs		Plant size (m3/day)
		380	1900	3800
Capital costs
	Land requirement (ha)	1.6	8	16
	Capital cost (million $)	0.49	1.12	1.18
	excluding land costs
	Amortized capital ($)	49905	114072	183 330
Operation and maintenance costs
	Labour ($10/h)	12500	30000	45000
	Power, 50-60/kWh	5883	11494	18600
	Parts and supplies	3500	4500	6500
	Total Operation and maintenance	21883	45994	70100
Total Cost ($)		71788	160066	253 430
Unit cost ($/m3/yr)		0.52	0.23	0.18

Effectiveness of the Technology

Biological treatment of wastewater by wetlands has been found to reduce the levels of virtually all contaminants, including those present in wastewater from mines (Fenessy and Mitsch, 1991). Wetlands are effective in reducing, by up to 90%, the concentrations of nitrogen, pathogenic bacteria and heavy metals in wastewater (Easson et al., 1988, citing Rogers et al., 1985). System performance, however, is determined by various factors, including water depth, temperature, pH, and dissolved oxygen concentrations, and by the type of wetland constructed or considered for use in wastewater treatment. Natural wetlands include shallow and deep water marshes, mangrove swamps, cypress domes, tidal marshes, bogs, and peatlands. Constructed wetlands may be artificially to reflect this diversity of wetland types.

Suitability

The suitability of wetland treatment systems for wastewater management depends on a wide range of conditions. Generally, large wetlands are more suitable for use as a treatment system because of their larger surface area, greater number and variety of aquatic plants and reduced susceptibility to flooding when wastewater is applied at a rate likely to be generated by a small municipality. Larger wetlands are also more likely to be able to treat wastewater on a year round basis. Smaller wetlands may become costly in the absence of mechanisms to control the rate and volume of wastewater applications.

Advantages

Wetland systems have several distinct advantages. Natural wetlands are immediately available without further need significant for the construction of facilities. In the case of constructed wetlands, wetland treatment systems also help to create additional wetland habitat. Wetlands may also provide an opportunity for partial cost recovery through the harvest of peat or vegetation for the use in the manufacture of pulp, compost, food for livestock, or vegetative material for biogas production.

Disadvantages

Disadvantages of the systems include climatic limitations on the active growth phase of the wetland vegetation and the land area required. A cold climate can become a limiting factor for the adoption of such a technology. The technology also requires relatively large areas which may not be readily available near cities or towns. Further, wetlands can produce nuisance insects. In cases where little is known of the relationships between various biotic and abiotic components of a wetland, the effects of using the wetland for water quality management purposes on the overall ecosystem may not be readily apparent.

Cultural Aspects

Health risks, along with other cultural barriers, make it difficult for the widespread adoption of wetland treatment technologies for wastewater treatment and reuse; people feel uneasy using wetlands where wastewater is treated for other economic purposes such as harvesting of vegetation or peat.

Further Development of the Technology

There is an high potential for the further development of wastewater treatment systems based upon wetlands in many parts of Asia. This potential can contribute to the reuse of wastewater in those areas where there is a growing demand for water. However, a cost effective means of pretreating wastewater to reduce pollution levels prior to discharging it to wetlands should be found.

References

Asian Institute of Technology (AIT) 1992. Sewage Purification Through Aquatic Plants, Final report. Division of Environmental Engineering, AIT, Bangkok.

Easson, M.E. et al. 1988. Sanitation Technologies for Cold/Temperate Climate. Environmental Sanitation Review, No. 25, AIT, Bangkok.

Fennessey, M.S. and W.J. Mitsch 1989. Design and Use of Wetlands for Renovation of Drainage from Coal Mines. In: Ecological Engineering: An Introduction to Ecotechnology, W.J. Mitsch and S.E.Jorgensen (eds), John Willey and Sons, New York.

2.4 Wastewater treatment using duckweed

Technical description

This is a relatively new technology in which small-scale wastewater treatment can be achieved using duckweed (Lemna spp. or Spirodela sp.). Duckweed is a self growing plant abundant in the tropical countries. It is commonly used as a fertilizer in paddy fields, but has recently been used in the treatment of wastewater in Bangladesh. In Mirzapur, Bangladesh, this technology has been implemented at the village level as part of a UNDP project examining the potential of duckweed-based wastewater treatment and fish production.

Operation and Maintenance

Use of this technology is simple, being based upon a modification of conventional maturation lagoon technology (see Wastewater Treatment Using Lagoons below). Maintenance consists of removal of excess biomass to encourage continued growth of the duckweed community, and thereby removal of nutrients from the wastewater, and maintenance of the containment structure of the pond.

Level of Involvement

This technology can be implemented at either the individual farm or community levels.

Costs

No data are available, but costs are estimated to be low.

Effectiveness of the Technology

Since 1989, PRISM, Bangladesh, has developed farming systems using duckweed-based technology and tested their potential for wastewater treatment and fish food. The results have been promising and, together with similar activities in Lima, Peru, have succeeded in generating interest among multilateral as well as bilateral donors in further examining the potential of this technology.

Suitability

This technology is suitable in tropical climates.

Advantages

This technology is inexpensive to construct and operate, and easy to implement. Duckweed is a prolific plant, especially in nitrogen-rich environments, and can be easily used as mulch or a natural soil organic enrichment.

Disadvantages

If the flows through the oxidation pond are not properly controlled, there is a possibility that the duckweed will flow out with the effluent. Treatment capacity may also be lost during high floods, if the area is not protected.

Cultural Aspects

No problems relating to the use of this technology are known to occur.

Further Development of the Technology

More research through pilot projects is needed in order to refine the sizing of the ponds used and to determine the correct innocculum of plant material to achieve a predetermined effluent quality.

Information Sources

Gert van Sanden, EMTAG, INUWS. The World Bank, 1818 H Street NW, Washington DC.

Jan van der Laan, DGIS, Royal Netherlands Embassy, New Delhi, India.

Erik S. Jensen, Danida, Royal Danish Embassy, Road 51, Gulshan, Dhaka, Bangladesh, Tel. 880 2 881799, Fax 880 2 883638.

Mohammed Ikramullah, PRISM, Bangladesh, House 67, Road 5A, Dhanmondi, Dhaka, Bangladesh, Tel./Fax 880 2 861-170.

Paneer Sehvam and Arun Mudgal, UNDP-World Bank Regional Water and Sanitation Group, 53, Lodi Estate, Post Office Box 416, New Delhi 110 003. India, Tel. 91-11 469 0488/9, Fax 91-11 462 8250.

2.5 Wastewater treatment using lagoons

Technical description

Lagoons play an important role as natural ecological wastewater treatment systems to reduce nutrient loading to water courses. The self-purification function of natural lagoons provide an opportunity for wastewater treatment prior to discharge or reuse. This method is especially suitable for tropical areas where there is a year round growing season and high incidence of solar irradiation. In this treatment method, wastes are degraded by various microbiological populations and pathogens can be effectively removed by aeration or exposure to sunlight. Lagoons are easy and inexpensive to construct and operate. Knowledge of this technology is quite advanced and information is readily available on the design of different types of lagoon systems. Lagoon systems are usually classified into four types: anaerobic, facultative, maturation and aerated lagoons. Each of these types is briefly described below, and more detail can be found in Yang and Wang (1990):

· Anaerobic lagoons are usually used for treatment of distillery and industrial wastes; for example, for the treatment of distillery wastewater in India.

· Facultative lagoons are usually used for removing toxic wastes. They utilise a relationship between bacteria and algae, and a balance between aerobic and anaerobic conditions to promote uptake of such chemicals.

· Maturation lagoons use micro algae and/or aquatic plants for wastewater treatment, especially for nitrogen removal.

· Aerated lagoons are an extended aeration, activated sludge process without sludge recycling. These systems usually require deeper stabilization ponds than the other types of lagoons with depths varying from 3 m to 5 m. This process is usually used for treating wastewater from both agricultural and industrial sources. It is also used for removal of nitrogen from chemically contaminated wastewaters.

Operation and Maintenance

This technology needs careful monitoring of flow rates and wastewater composition which can affect the various biochemical processes. Lagoons are best suited for domestic wastewater treatment, although, depending on the species composition of the floral and microbial communities, can be used for agricultural and industrial treatment. Certain species of plants can be very effective in removing heavy metals and similar contaminants from the waste stream.

Level of Involvement

This technology is typically implemented at the project level.

Costs

No data are available but costs are estimated to be relatively low for matruation or oxidation ponds. Costs for Aerated lagoons can be higher depending on the volume of wastewater to be treated.

Effectiveness of the Technology

A study carried out on Lake Biwa, Japan, by Kurata and Satouchi (1989) showed that the Nishinoko Lagoon has played an important role in removing nutrients from wastewater flowing into the lake. Lake Biwa is the largest freshwater lake in Japan, and is surrounded by many large and small lagoons. Eutrophication of the lake has occurred due to inflow of both domestic wastewater and runoff from cultivated areas in the lake watershed. The self-purification phenomenon within these lagoons has provided a means for wastewater treatment and treatment of runoff from cultivated fields which has reduced the level of enrichment within the lake.

In contrast to the use of lagoons for primary treatment of wastewater, maturation lagoons are considered as a tertiary treatment process and are commonly used after a series of other ponds. Maturation lagoons are fully aerobic and are usually used for microorganism removal. The performance of the ponds, however, depends upon pond hydraulic behaviour, pond depth, solar radiation, coliform decay per unit of solar radiation, and the light extinction coefficient. These factors have to be considered while considering the use of a maturation lagoon system for wastewater treatment (Yang and Wang, 1990).

Suitability

This technology is suitable in areas where natural lagoons exist near large waterbodies, or in areas where artificial ponds can be constructed.

Advantages

Lagoons can protect the main freshwater body by retaining pollutants. Disadvantages

There is a risk of exacerbating water pollution problems if the lagoons are not properly controlled, especially if natural lagoons are used. Further, the additional pollutants loadings arising from the input of wastewaters reduces the assimilative capacity of natural lagoons and their ability to buffer the larger waterbody from stormwater pollutant loads.

Cultural Aspects

There are no known problems associated with the use of this technology.

Further Development of the Technology

Further research, through pilot projects, is needed to fully understand the consequences of using natural lagoon systems for wastewater treatment. The use of artificial lagoons, howver, is a well-understood, conventional wastewater treatment technology.

Information Sources

Contacts

Environment and Sanitation Information Center (ENSIC), Asian Institute of Technology, Post Office Box 4, Klong Luang, Pathumthani, Bangkok, Thailand, Tel. 66 2 516 0110, Fax 66 2 516 2126, E-mail: [email protected].

Bibliography

Kurata, A. and M. Satouchi 1989. Function of a Lagoon in Nutrient Removal in Lake Biwa, Japan, In: Ecological Engineering: An Introduction to Ecotechnology, W.J. Mitsch and S.E. Jorgensen (eds), John Willey and Sons, New York.

Yang, P.Y. and M.L. Wang 1990. Biotechnology Applications in Wastewater Treatment, Environment and Sanitation Information Centre Paper No. 29, AIT, Bangkok, Thailand.

2.6 Other technologies of wastewater treatment and reuse

Technology Description

In Southeast Asian countries, including Hold Kong, urban and surrounding areas are the centres of rapid expansion. The resources required to manage municipal, industrial and agro-industrial wastes are very often severely strained. Thus, economic growth is often accompanied by ecological damage, as industries generate considerable amounts of both solid and liquid waste products. Waste management is therefore an urgent environmental consideration. Conventional freshwater augmentation technologies involve different wastewater treatment processes such as preliminary or primary treatment; secondary treatment; and tertiary or advanced treatment techniques. As with any other environmental problem, new methodologies for improved waste handling and treatment rely on advancements in related sciences and technologies. In recent years, biological treatment of wastes has developed rapidly because of breakthroughs in biotechnology. Biologically-based technologies, therefore, are becoming an area of increasing importance as a mean of water pollution abatement and environmental rehabilitation. Nevertheless, with both conventional and bio technological wastewater treatment techniques, waste materials, when properly managed and treated, should not cause any appreciable environmental damage (Whitton and Wong, 1994).

Preliminary Treatment. Preliminary treatment is basically screening of settleable organic and inorganic solids by sedimentation and removal of materials. Approximately, about 25% to 50% of the incoming BOD₅, 50% to 70% of the suspended solids, and 65% of the oil and grease is removed during the preliminary or primary treatment process. This process largely reduces the volume to be treated through secondary and advanced treatment processes, and, for some purposes such as irrigation of orchards and vineyards, may be considered sufficient treatment for reuse, depending upon the local acceptance. A bar screen made of long, narrow, metal bars spaced at 25 mm is used for preliminary treatment. The primary treatment process consists of grit removal. Basically two types - horizontal flow and aerated types - of grit removal techniques are used. Primary settling tanks are then used to remove the readily settleable solids prior to further treatment. The treatment process involves chemical treatment and flocculation, and passage through second and third stage settling tanks. A study by Chen (1993) to evaluate the effectiveness of primary treatment of municipal wastewater before discharge into the ocean indicated that the removal of suspended solids was always less than 50% while COD and BOD₅ removals were in the range of 23% to 41% and 15% to 27%, respectively.

Secondary Treatment. The main purpose of secondary treatment is to remove non-settleable solids remaining in the wastewater stream after the preliminary and primary treatment process. Efficiency is estimated at about 85% removal of BOD₅. This technique involves biochemical processes for the oxidative or reductive degradation of biodegradable organic pollutants, and includes such technologies as the anaerobic and facultative ponds as well as aerated lagoons previously described.

Fish Farming or Aquaculture. Fish farming has been used extensively to assist in the treatment of wastewater. It helps to reduce the levels of suspended solids and algal growth in the wastewater, and improves the quality of the final effluent, which may be used subsequently for crop irrigation and other uses. Wastewater treatment using fish ponds is a natural process that degrades and stabilizes organic wastes, while fertilizing a fish pond with organic wastes to stimulate the growth of natural biota, especially microorganisms which serve as fish food (Edwards, 1985). Systems consist of both dry and wet variants. The dry systems utilize nightsoil or faecally contaminated surface water, applied to the pond bottoms during the dry season, for aquacultural purposes in artificial ponds. The wet systems, which remain water-filled throughout the year, use similar nutrient sources to drive fish production in enclosures within ponds and natural lakes. These kinds of systems have been widely used in several Asian countries (Edwards, 1985).

Overland Flow Systems. Overland flow systems pass wastewater across slightly sloping grasslands which provide both filtration and erosion control. The technology is similar to the conventional trickling filter technology applied in traditional secondary treatment processes. When wastewater is passed across sloping grasslands, the contaminants are retained by filtration and adsorption, and organic contaminants are decomposed under primarily aerobic conditions. Intermittent feeding from parallel lanes provides aeration to the root zones of the grasses and avoids flooding of the treatment plots. In this process, the wastewater remains in contact with open air. This results in a relatively high dissolved oxygen content at the outlet of the system and helps to aerate the effluent without the need for additional energy. The efficiency of this method largely depends on the selection of the grass species, and is further influenced by specific local soil and climatic conditions. Common grasses used in this technology are paragrass (Braciera muticia), chestnut (Eleocharis dulcis), red sprangle top (Leptochola chinensis). Studies carried out at the Asian Institute of Technology (AIT, 1992) indicate that the overland flow system designed with paragrass in main lane and with other two grasses in other parallel lanes were effective in removing 80% of the suspended solids, 47% of the BOD₅, 39% of the organic nitrogen, and 19% of the total phosphorus at the loading rate of 532 m³/week. This system is more effective in removing suspended solids than dissolved solids, but the research indicates that combined pond and overland flow systems can result in an high quality effluent. Combination systems also work well where the treatment requirements are high or the land available is insufficient.

Integrated Biological Pond Systems. The feasibility of an inexpensive wastewater treatment system based upon the principles of aquatic biology was evaluated by Wu et al. (1993), and an integrated biological pond system was constructed and operated for more than 3 years to purify the wastewater from a medium-sized city in Central China. The experiment was conducted in three phases, using different treatment combinations for testing their purification efficiencies. The pond system was divided into three functional regions: an influent purification area, an effluent upgrading area, and a multi-utilization area. These functional regions were further divided into several zones and subzones, each representing a particular ecosystem component. Various kinds of aquatic macrophytes, algae, microorganisms and zooplankton were effectively cooperating in the wastewater treatment in these zones within this integrated system. The system attained high reductions of BOD₅, COD, TSS, TN, TP and other pollutants. The purification efficiencies of this system were higher than those of most traditional oxidation ponds or ordinary macrophyte ponds. Mutagenic effects and numbers of bacteria and viruses declined significantly during the process of purification, and, after the wastewater flowed through the upgrading zone, the concentrations of pollutants and algae evidently decreased. However, plant harvesting did not significantly affect the levels of reductions of the main pollutants achieved, although it did significantly affect the biomass productivity of the macrophytes. The effluent from this system could be utilized in irrigation and aquaculture. Some aquatic products were harvested from this system and some biomass was utilized for food, fertilizer, fodder and related uses. Finally, the treated wastewater discharged from the system was reclaimed for various purposes.

Advanced Wastewater Treatment Systems. Some contaminants, such as inorganic substances and a sizeable portion of microbiological populations, present in the waste stream remain in the effluent after the preliminary and secondary treatment processes. Amongst others, nitrates, phosphates and ammonia radicals may still be found in high concentrations. These pollutants can be removed through advanced treatment processes using autotrophic plants to take up nutrients and selected heavy metals and organic substances, flocculation of colloidal particulate matter with chemical flocculants, and removal of synthetic organic contaminants using absorbents and the oxidizing agents. Technologies used in advanced wastewater treatment systems include filtration, carbon adsorption, microstraining, chemical phosphorus removal, and biological nitrogen removal (Shah, 1994).

Filtration can remove most of the residual suspended solids, BOD₅, and bacteria from the secondary effluent using multimedia or microstrainer filters. Multimedia filters contain low density charcoal for removal of particles with large grain sizes, medium density sand for intermediate sizes, and a high density medium for the smallest grain sizes. These filters can decrease the concentration of suspended solids in activate sludge-treated effluent from 25 mg/l to approximately 10 mg/l (Shah, 1994). The carbon adsorption technique is used also to adsorb persistent organic substances onto activated carbon, the organic removal capacity of which depends on the surface area of the carbon particles within the cartridge. Microstrainers can also be used to remove residual suspended solids. These filters consist of woven steel wire or a special cloth fabric mounted on revolving drums which capture the solids still remaining in the wastewater.

Only about 20% of the phosphorus in domestic wastewater is removed during secondary treatment. With phosphorus removal techniques, phosphorus is removed through chemical precipitation of the phosphorus with aluminum sulphate (alum), ferric chloride, or calcium carbonate (lime). This process requires a reaction basin and settling tank to remove the precipitate. Likewise, nitrogen is removed either chemically or biologically. The chemical process is called ammonia stripping and the biological process is called nitrification/denitrification. In the ammonia stripping process, nitrogen is removed in two stages by first raising the pH to convert ammonium into ammonia, and then stripping the ammonia by passing large volume of air through the effluent. In the biological process, secondary effluent is further aerated to convert ammonia nitrogen to nitrate nitrogen.

Wastewater Treatment and Reuse in India In Calcutta, India, systematic reuse of wastewater for aquaculture started in the early 1940s. The sewage-fed fish ponds were initially created on about 4 628 ha in an 8 000 ha wetland area. As of 1987, about 3 000 ha of ponds remained active. The treatment process involves screening the raw sewage prior to it entering the ponds. After twelve days, the ponds are repeatedly netted and manually agitated using split bamboo rods. The agitation enhances the oxidation and mixing of the effluent, and promotes improved water quality. The pond is stocked with fish after 25 days, and additional sewage effluent is applied to the ponds during a 3 hour period in the morning, 7 days/month at an estimated rate of 130 m3/day/ha. Even though the total fish pond area has been reduced over the period of operation, total production and yield of fish has gone up from 0.6 tones/ha in 1948 to between 4 and 9 tones/ha in 1984. (Source: FAO, 1992; Edwards, 1985,1990; and Ghosh. 1984)

During the denitrification processes, nitrate nitrogen is converted to gaseous nitrogen by bacteria under anaerobic conditions. Using these techniques, Chen (1993) found that the addition of polyaluminium-chloride (PAC) resulted in a 70% removal of suspended solids at a PAC dosage rate of 30 mg/l. If polyelectrolytes are added (at a rate of about 1 mg/l), the dosage of PAC could be reduced to around 10 mg/l with a similar result. Air flocculation, or dissolved air flotation filtration (DAFF), followed by sedimentation, resulted in the removal of more than 80% of the suspended solids at an aeration rate of 0.5-1.0 Nl air/l. This technology is more effective for smaller solids than for larger solids in wastewater. Organic removal, with either sedimentation or combined air flocculation and sedimentation processes, removed about 15% to 40% of the COD or BOD₅. The efficiency of organic removal from wastewater was increased to about 60% by utilizing chemical coagulation and sedimentation treatment.

The use of advanced treatment is only recommended where major pollutants are not removed to a sufficient extent by the secondary treatment. Usually, advanced treatment are very complicated and expensive, and its use in developing countries to produce suitable effluent for aquaculture or farm purposes is not recommended (FAO, 1993).

Reuse of Wastewater in Irrigation. In the face of growing water scarcity, reuse of marginal quality water is the best alternative available for agriculture. Marginal quality water, as defined by FAO (1992), refers to water that possesses certain characteristics (such as agricultural drainage water, municipal wastewater, and brackish water) which have the potential to cause problems when the water is used for purposes other than the intended use. Converting marginal quality water to freshwater that can be used for agricultural purposes requires less complex treatment technologies than those required to produce a multi-purpose quality water. Further, use of wastewater for agriculture mimics the traditional use of night soils for agricultural purposes that has been practised in different parts of Asia from ancient times. Sewage farming was initiated in Bombay, India, as early as 1877, and, in Delhi, from 1913 (Shuval et al., 1986). In modem times, the most intensive use of wastewater for irrigation has been made in Israel. In India, modem use of sewage effluents for irrigation is reported to be about six decades old. China's sewage irrigation systems have developed rapidly since 1958. In Laos, effluent of sewage is used directly for the irrigation of 400 to 500 ha fields.

Wastewater Recycling in China: Application of Conventional Technologies Municipal wastewater: Wastewater treatment and reuse in China has a long history, beginning in 1956 in North China. Municipal wastewater is treated to primary and secondary standards, with secondary treatment being provided by i) conventional activated sludge processes; ii) contact stabilization processes; and iii) pare oxygen aeration processes. In some cases, natural biological treatment facilities such as oxidation ponds and sewage irrigation systems are used as secondary treatment alternatives. Presently, wastewater from cities and towns in China amounts to about 99.6 million m3 of water. Industrial wastewater. Both activated sludge systems and fixed film systems are widely used for treating organic industrial wastewater in China. The activated sludge systems are both mixed systems and ontact-stabilization systems. The fixed film systems are mainly rotating biological contactor systems, contact aeration systems, and biological tower systems. Efficiency is good, removing both BOD5 (95%) and COD (75%), but diminishes in the case of colour (50%), with the efficiency of me combined tanks being inferior to that of separate tanks in which me aeration and settling tanks are constructed separately. Secondary treatment plants, using technologies such as sedimentation - dissolved air floatation - activated sludge, or tertiary treatment plants. using technologies such as mechanical -activated sludge - activated carbon absorption or zonation, exist in cities like Shanghai, Nanking and Beijing. (Source: Ku, 1982)

Reuse of irrigation drainage water provides another important source of water for agricultural purposes. Conventional irrigation methods, such as flood or spray irrigation, result in excess water being applied to agricultural fields. The runoff that results, referred to as drainage water or return flows, may be collected and reused for irrigation purposes downstream. This practice, which is widespread though not well documented, can be found in many farmer-managed irrigation systems of Nepal, India and Thailand. In western hills of Argakhachi, Nepal, five parallel canals run across the base of the hills and successively collect drainage water from the farming areas upslope for reuse downstream. In the Kailai Terhi-Gurgi irrigation system, farmers have constructed parallel drainage networks to collect drainage water in the upper portions of the system for reuse in the lower portions of the area. The exact quantities of water reused through this process are not known. In some cases, rules have been formulated for the allocation of rights to reuse drainage water. In arid zones, such as in Egypt, drainage water is collected by an extensive network of covered and open drains and reused. The quantity of drainage water collected and reused during the 1988/89 hydrological year was estimated to be 2 634 million m³. The drainage water available for reuse had a salinity content within the limit of 1.5 mS/cm (Abu-Zeid et al., 1991), but the quantity of water available was reported to be decreasing and the salinity increasing.

In Tainan, Taiwan, night soil is spread over the bottoms of ponds which are empty during the winter, with additional night soil being added at intervals, about 4 to 5 times during the growing season. Several thousand hectares of ponds exist.

TABLE 8. Cost Comparison of Various Wastewater Treatment Processes.

Rank (1=best)	Initial Cost	Operation & Maintenance Cost	Life Cycle Cost	Operability	Reliability	Land Area	Sludge Production	Power Use	Effluent Quality
1	MA	SP	MA	SP	SP	MA	SP	SP	SP
2	AS	MA	AS	AL	AL	AS	AL	MA	AL
3	OD	AL	OD	OD	OD	OD	OD	AS	MA
4	AL	AS	AL	AS	MA	AL	AS	AL	OD
5	SP	OD	SP	MA	AS	SP	MA	OD	AS

SP, Stabilization Ponds; AL, Aerated Lagoons; OD, Oxidation Ditches; AS, Conventional Activated Sludge; MA, Modified Aeration Activated Sludge or Trickling Filter Solids Contactor

Note: Flexibility and expandability are similar for all types.
Source: BMA (1990)

In Bangladesh, overhanging latrines are constructed to supplement the water and nutrient supply to fish ponds during the dry season. The ponds, constructed near housing units, may be dry for part of the year and are usually filled with floodwater during the rainy season. Fish, entering the ponds with the floodwater, grow rapidly in the nutrient-rich ponds and are harvested prior to the ponds drying out. Similar systems can be found also in West Java, Indonesia, where about 25% offish ponds of 1 000 m² or less in areal extent have overhanging latrines associated with them.

Wet pond aquaculture systems have been used mainly in Calcutta, India, and in China, where fish cultivation in wastewater is carried out in about 670 ha of ponds in 42 cities. The yields of the wastewater-fed fish ponds were about 3 to 4 times greater, and operating costs about 50% less, that those of conventional ponds.

In the Bangkok Metropolitan Area (BMA), Thailand, the modified aeration, activated sludge wastewater treatment method was found to have lowest initial cost, while stabilization ponds had the highest.

Table 8 shows the rankings of the various treatment technologies evaluated, according to operation and maintenance costs, operational ease and flexibility, land area required, power usage, and effluent quality.

Level of Involvement

These technologies can be implemented as both private and the governmental initiatives, as in China, or as local or private industrial initiatives, as in other countries. In most developing countries, innovative approaches that would encourage the increased use of such technologies have been hampered due to the absence of concrete regulatory measures and enforcement mechanisms, and, possibly, by government control of public water supply and sanitation systems.

Cultural Acceptability

People feel uneasy about the reuse of treated wastewater. Further, there are several public health hazards associated with the reuse of wastewater, especially associated with aquaculture systems. The risks are related to the potential for exposure to public health hazards during the transportation and application of night soils, and the consumption of contaminated organisms, and to the potential for the spread of disease by encouraging the spread disease vectors, such as mosquitos. These health risks, along with other cultural barriers, make the widespread adaptation of such technologies for wastewater treatment and reuse difficult.

Wastewater Recycling in Industries: An Example from Bangkok The Phoenix Pulp and Paper Co., the largest paper mill in the Northeast Province of Thailand, is currently using and discharging process water at a rate of about 30 000 m3/day. The mill located next to the Nam Pong River la Khon Kaen, is proposing to spend about $ 26 million to recycle its wastewater for reuse within the company compound, instead of discharging it into the nearby river and eucalyptus plantations. This proposal comes at a time when the Thai government is expected to ban effluent discharges. The company also aims to reduce its effluent to about 20 000 m3/day by using new technologies to produce pulp products. This reduction will also reduce the volume of effluent discharged to eucalyptus plantations under "Project Green", and help to control seepage damage in neighbouring rice fields, which has cost the company about $86 000 in compensation to about 100 villagers, Source: Bangkok Post August 9,1995; Mill May Use Up Recycled Water, p.3.

Further Development of the Technologies

The further development of wastewater technologies has a high potential in many parts of Asia, especially in Thailand, India and China. With the growing demand for water in the urban sector, more and more water suitable for potable use will be diverted to urban areas, increasing the need to use waters of marginal quality in aquaculture and irrigation fanning. The adoption of wastewater treatment and reuse technologies, however, will depend on many factors. Government and planners have to develop and facilitate such mechanisms to encourage people to adopt such technologies. Motivating mechanisms include environmental concerns - it is better to use treated wastewater for economic purposes rather, than directly discharging it to waterways and decreasing the waste assimilative capacity of the water courses, economic concerns - reuse of wastewater for aquaculture and irrigation can help reduce the pressure for public investment in large (and costly) water resources development projects; and legal concerns - regulatory and economic instruments can provide direct incentives to polluters to use treated wastewater for aquaculture and farm purposes.

Government Initiatives and the Future of Municipal Effluent Reuse for Irrigation Land application of treated wastewater is a low-energy treatment system, providing economic returns from the reclamation of wastewater, especially in areas with acute shortages of water and nutrients. Research carried out at China's Beijing Agricultural University (BEU) and the India's National Environmental Engineering Research Institute (NEERI) concluded that, compared to other conventional secondary treatment methods, land application was generally better for the removal of pollutants. Because of the potential expansion of wastewater reuse technologies, these institutes have established a monitoring network. In India, NEERI has conducted research on the problems arising from sewage farming, crop and soil responses to different wastewater treatments, the formulation of guidelines for sewage fanning systems, and direct and indirect health effects. As part of India's VIIth Plan, a multi-locational framework is envisaged, including regional research centres linked with Technology Transfer Centres that will implement 100 new schemes for sewage and sullage utilization in selected cities and townships. In China, BAU has been actively carrying out an investigation of the environmental impacts of sewage irrigation systems. Several methods to measure the environmental quality in the study areas have been developed. The methods include identification of the pollution concentrations in crops irrigated with treated wastewater. (Source: RAPA, 1985).

Information Sources

Abu-Zeid, M. and S. Abdel-Dayen 1991. Variation and Trends in Agricultural Drainage Water Re-use in Egypt. Water International, 4, 247-253.

Bangkok Metropolitan Administration 1990. Pre-feasibility Study on Private Wastewater Treatment for BMA, Office of the Prime Minister, Thailand.

Edwards, P. 1985. Aquaculture: A Component of Low Cost sanitation Technology. World Bank Technical Paper No. 36, Integrated Resource Recovery, The World Bank, Washington DC.

FAO (Food and Agriculture Organization of the United Nations) 1992. Wastewater Treatment and Use in Agriculture, FAO Irrigation and Drainage Paper 47, FAO, Rome.

FAO (Food and Agriculture Organization of the United Nations) 1993. Integrated Rural Water Management. FAO Irrigation and Drainage Paper, FAO, Rome.

Ghosh, G. and P.N. Phadtare 1990. Environmental Effects of the Groundwater Resources of the Multiaquifer system of North Gujarat Area, India. In: Proceedings of International Conference on Groundwater Management, AIT, Bangkok.

Ku, H. 1982. The Status and Trend of Water Pollution Control Technology in China. Water International, 7, 78-82.

Regional Office for the Asia and Pacific (RAPA)/FAO 1985. Organic recycling in Asia and Pacific, RAPA Bulletin, 2/85, Bangkok.

Shah, K.L. 1994. An Overview of Physical, Biological, and Chemical Processes for Wastewater Treatment, In: Process Engineering for Pollution Control and Waste Minimization, D.L. Wise et al. (Eds), Marcel Dekker, Inc. New York.

Shuval, H.I. et al. 1986. Integrated Resource Recovery: Wastewater Irrigation in Developing Countries, World Bank Technical Paper No. 51, The World Bank, Washington DC.

3.1 General rainwater harvesting technologies

Rainwater harvesting, in its broadest sense, can be defined as the collection of runoff for human use. The collection processes involve various techniques such as the collection of water from rooftops and the land surface, as well as within water courses. These techniques are widely used in Asia both for meeting drinking water supply needs and for irrigation purposes.

Technical Description

Rainwater harvesting is a technology used for collecting and storing rainwater from rooftops, the land surface or rock catchments using simple techniques such as jars and pots as well as more complex techniques such as underground check dams. The techniques usually found in Asia and Africa arise from practices employed by ancient civilizations within these regions and still serve as a major source of drinking water supply in rural areas. Commonly used systems are constructed of three principal components; namely, the catchment area, the collection device, and the conveyance system.

· Catchment Areas

Rooftop catchments: In the most basic form of this technology, rainwater is collected in simple vessels at the edge of the roof. Variations on this basic approach include collection of rainwater in gutters which drain to the collection vessel through down-pipes constructed for this purpose, and/or the diversion of rainwater from the gutters to containers for settling particulates before being conveyed to the storage container for the domestic use. As the rooftop is the main catchment area, the amount and quality of rainwater collected depends on the area and type of roofing material. Reasonably pure rainwater can be collected from roofs constructed with galvanized corrugated iron, aluminium or asbestos cement sheets, tiles and slates, although thatched roofs tied with bamboo gutters and laid in proper slopes can produce almost the same amount of runoff less expensively (Gould, 1992). However, the bamboo roofs are least suitable because of possible health hazards. Similarly, roofs with metallic paint or other coatings are not recommended as they may impart tastes or colour to the collected water. Roof catchments should also be cleaned regularly to remove dust, leaves and bird droppings so as to maintain the quality of the product water. Figure 1 shows a schematic of a rooftop collection system.

Figure 1. Rooftop Catchment System.

Land surface catchments: Rainwater harvesting using ground or land surface catchment areas is less complex way of collecting rainwater. It involves improving runoff capacity of the land surface through various techniques including collection of runoff with drain pipes and storage of collected water (Figure 2). Compared to rooftop catchment techniques, ground catchment techniques provide more opportunity for collecting water from a larger surface area. By retaining the flows (including flood flows) of small creeks and streams in small storage reservoirs (on surface or underground) created by low cost (e.g., earthen) dams, this technology can meet water demands during dry periods. There is a possibility of high rates of water loss due to infiltration into the ground, and, because of the often marginal quality of the water collected, this technique is mainly suitable for storing water for agricultural purposes. Various techniques available for increasing the runoff within ground catchment areas involve: i) clearing or altering vegetation cover, ii) increasing the land slope with artificial ground cover, and iii) reducing soil permeability by the soil compaction and application of chemicals.

Figure 2. Ground Catchment System.

Clearing or altering vegetation cover: Clearing vegetation from the ground can increase surface runoff but also can induce more soil erosion. Use of dense vegetation cover such as grass is usually suggested as it helps to both maintain an high rate of runoff and minimize soil erosion.

Increasing slope: Steeper slopes can allow rapid runoff of rainfall to the collector. However, the rate of runoff has to be controlled to minimise soil erosion from the catchment field. Use of plastic sheets, asphalt or tiles along with slope can further increase efficiency by reducing both evaporative losses and soil erosion. The use of flat sheets of galvanized iron with timber frames to prevent corrosion was recommended and constructed in the State of Victoria, Australia, about 65 years ago (Kenyon, 1929; cited in UNEP, 1982).

Soil compaction by physical means: This involves smoothing and compacting of soil surface using equipment such as graders and rollers. To increase the surface runoff and minimize soil erosion rates, conservation bench terraces are constructed along a slope perpendicular to runoff flow. The bench terraces are separated by the sloping collectors and provision is made for distributing the runoff evenly across the field strips as sheet flow. Excess flows are routed to a lower collector and stored (UNEP, 1982).

Soil compaction by chemical treatments: In addition to clearing, shaping and compacting a catchment area, chemical applications with such soil treatments as sodium can significantly reduce the soil permeability. Use of aqueous solutions of a silicone-water repellent is another technique for enhancing soil compaction technologies. Though soil permeability can be reduced through chemical treatments, soil compaction can induce greater rates of soil erosion and may be expensive. Use of sodium-based chemicals may increase the salt content in the collected water, which may not be suitable both for drinking and irrigation purposes.

Figure 3. Rock Catchment System.

Rock catchments systems: The presence of massive rock outcrops provides suitable catchment surfaces for freshwater augmentation (Figure 3). In these systems, runoff is channelled along stone and cement gutters, constructed on the rock surface, to reservoirs contained by concrete dams. The collected water then can be transported through a gravity fed pipe network to household standpipes.

· Collection Devices

Storage tanks: Storage tanks for collecting rainwater harvested using guttering may be either above or below the ground. Precautions required in the use of storage tanks include provision of an adequate enclosure to minimise contamination from human, animal or other environmental contaminants, and a tight cover to prevent algal growth and the breeding of mosquitos. Open containers are not recommended for collecting water for drinking purposes. Various types of rainwater storage facilities can be found in practice. Among them are cylindrical ferrocement tanks and mortar jars. The ferrocement tank consists of a lightly reinforced concrete base on which is erected a circular vertical cylinder with a 10 mm steel base. This cylinder is further wrapped in two layers of light wire mesh to form the frame of the tank. Mortar jars are large jar shaped vessels constructed from wire reinforced mortar. The storage capacity needed should be calculated to take into consideration the length of any dry spells, the amount of rainfall, and the per capita water consumption rate. In most of the Asian countries, the winter months are dry, sometimes for weeks on end, and the annual average rainfall can occur within just a few days. In such circumstances, the storage capacity should be large enough to cover the demands of two to three weeks. For example, a three person household should have a minimum capacity of 3 (Persons) × 90 (l) × 20 (days) = 5 400 l.

Rainfall water containers; As an alternative to storage tanks, battery tanks (i.e., interconnected tanks) made of pottery, ferrocement, or polyethylene may be suitable. The polyethylene tanks are compact but have a large storage capacity (ca. 1 000 to 2 000 l), are easy to clean and have many openings which can be fitted with fittings for connecting pipes. In Asia, jars made of earthen materials or ferrocement tanks are commonly used. During the 1980s, the use of rainwater catchment technologies, especially roof catchment systems, expanded rapidly in a number of regions, including Thailand where more than ten million 2m³ ferrocement rainwater jars were built and many tens of thousands of larger ferrocement tanks were constructed between 1991 and 1993. Early problems with the jar design were quickly addressed by including a metal cover using readily available, standard brass fixtures.

The immense success of the jar programme springs from the fact that the technology met a real need, was affordable, and invited community participation. The programme also captured the imagination and support of not only the citizens, but also of government at both local and national levels as well as community based organizations, small-scale enterprises and donor agencies. The introduction and rapid promotion of Bamboo reinforced tanks, however, was less successful because the bamboo was attacked by termites, bacteria and fungus. More than 50 000 tanks were built between 1986 and 1993 (mainly in Thailand and Indonesia) before a number started to fail, and, by the late 1980s, the bamboo reinforced tank design, which had promised to provide an excellent low-cost alternative to ferrocement tanks, had to be abandoned.

The design considerations vary according to the type of tank and various other factors have to be considered while designing the rainwater tanks (Latham and Gould, 1986; Gould, 1992) which are:

- A solid, secure cover to keep out insects, dirt and sunlight which will act to prevent the growth of algae inside the tank.

- A coarse inlet filter for excluding coarse debris, dirt, leaves, and other solid materials. An overflow pipe.

- A manhole, sump and drain for cleaning.

- An extraction system that doesn't contaminate the water (e.g., a tap or pump). A lock on the tap.

- A soakaway to prevent spilled water from forming puddles near the tank.

- A maximum height of 2 m to limit the water pressure acting on the container to minimize burst tanks.

- A device to indicate the level of water in the tank. A sediment trap, tipping bucket or other fouled flush mechanism.

- A second, clear water storage tank if the rainwater has to be subjected to some form of water treatment, such as desalination using a density stratification process in the first tank.

· Conveyance Systems

Conveyance systems are required to transfer the rainwater collected on the rooftops to the storage tanks. This is usually accomplished by making connections to one or more down-pipes connected to the rooftop gutters. When selecting a conveyance system, consideration should be given to the fact that, when it first starts to rain, dirt and debris from the rooftop and gutters will be washed into the down-pipe. Thus, the relatively clean water will only be available some time later in the storm. There are several possible choices to selectively collect clean water for the storage tanks. The most common is the down-pipe flap. With this flap it is possible to direct the first flush of water flow through the down-pipe, while later rainfall is diverted into a storage tank. When it starts to rain, the flap is left in the closed position, directing water to the down-pipe, and, later, opened when relatively clean water can be collected. A great disadvantage of using this type of conveyance control system is the necessity to observe the runoff quality and manually operate the flap. An alternative approach would be to automate the opening of the flap as described below.

A simple and effective method of diverting rainwater without the need for supervision is depicted in Figure 4. A funnel-shaped insert is integrated into the down-pipe system. Because the upper edge of the funnel is not in direct contact with the sides of the down-pipe, and a small gap exists between the down-pipe walls and the funnel, water is free to flow both around the funnel and through the funnel. When it first starts to rain, the volume of water passing down the pipe is small, and the "dirty" water runs down the walls of the pipe, around the funnel and is discharged to the ground as is normally the case with rainwater guttering. However, as the rainfall continues, the volume of water increases and "clean" water fills the down-pipe. At this higher volume, the funnel collects the clean water and redirects it to a storage tank. The pipes used for the collection of rainwater, wherever possible, should be made of plastic, PVC or other inert substance, as the pH of rainwater can be low (acidic) and could cause corrosion, and mobilization of metals, in metal pipes.

Figure 4. Typical Conveyance System

In order to safely fill a rainwater storage tank, it is necessary to make sure that excess water can overflow, and that blockages in the pipes or dirt in the water do not cause damage or contamination of the water supply. The design of the funnel system, with the drain-pipe being larger than the rainwater tank feed-pipe, helps to ensure that the water supply is protected by allowing excess water to bypass the storage tank. A modification of this design is shown in Figure 5, which illustrates a simple overflow/bypass system. In this system, it also is possible to fill the tank from a municipal drinking water source, so that even during a prolonged drought the tank can be kept full. Care should be taken, however, to ensure that rainwater does not enter the drinking water distribution system.

Figure 5. Typical Distribution System

Calculating the Amount Available: When using rainwater for water supply purposes, it is important to recognize the fact that the supply is not constant throughout the year and plan an adequately-sized storage system to provide water during dry periods. A knowledge of the rainfall quantity and seasonality, the area of the collection area and volume of the storage container, and quantity and period of use during which water is required for water supply purposes is critical. For example, in Tokyo, the average annual rainfall is 1 800 mm, and, assuming that the effective collection area of a house is equal to its roof area, the typical collection area is about 100 m². Thus, the average annual volume of rainwater falling on the roof may be calculated as the product of the collection area, 100 m², and rainfall amount, 1 800 mm, or 180 m³. However, in practice, this volume can never be achieved since a portion of the rainwater evaporates from the rooftop and a portion, including the first flush, may be lost to the drainage system. Additional rainwater volume may be lost as overflow from the storage container if the storage tank is of insufficient volume to contain the entire volume of runoff. Thus, the net usable or available amount of rainwater from a tiled roof would be approximately 70% to 80% of the gross volume of rainfall, or about 130m³ to 140m³ if the water container is big enough to hold that quantity of rainwater available. Such a volume would be sufficient to save a significant amount of freshwater and money.

Estimation of the Required Volume of Water: The individual daily rate of water consumption per person tends to be variable and may be difficult to calculate. Statistics vary from 130 l to 175 l per person per day in developing countries. Of this volume, at least half is used for purposes for which water of a lesser quality would suffice. Indicative volumes are shown in Table 9, which summarizes the volumes of water used for household purposes, and indicates possibilities for the use of rainwater to supplement a municipal supply. Table 9 clearly shows that approximately 80 to 95 l of the average daily volume of water consumed per person could be provided by the use of rainwater.

TABLE 9. Typical Per Capita Volume of Daily Water Consumption

Municipal Water Utilization	Possible Rainwater Utilization
Highest quality	High quality	Low quality
Drinking/Cooking: 3-6 l	Washing dishes: 8-10 l	Toilet/Sanitation: 40-50 l
Body care: 8 l	Washing clothes: 16 l	Other uses: 12 l
Shower/Bath: 40-50 l	Watering garden: 7 l
Total: 50-65 l	Total: 30-33 l	Total: 52-62 l

Indicative Rate of Water Use

1 flushing of toilet:	9 l	1 bathtub full:	140 l
1 washing machine load:	60 l	1 shower:	40 l

Extent of Use

The history of rainwater harvesting in Asia can be traced back to about the 9th or 10th Century and the small-scale collection of rainwater from roofs and simple brush dam constructions in the rural areas of South and South-east Asia. Rainwater collection from the eaves of roofs or via simple gutters into traditional jars and pots has been traced back almost 2 000 years in Thailand (Prempridi and Chatuthasry, 1982). Rainwater harvesting has long been used in the Loess Plateau regions of China. More recently, however, about 40 000 well storage tanks, in a variety of different forms, were constructed between 1970 and 1974 using a technology which stores rainwater and stormwater runoff in ponds of various sizes (see case studies in Part C, Chapter 5). A thin layer of red clay is generally laid on the bottom of the ponds to minimize seepage losses. Trees, planted at the edges of the ponds, help to minimize evaporative losses from the ponds (UNEP, 1982).

Rainwater Harvesting Project in The Philippines In The Philippines, rainwater harvesting was initiated in 1989 with the assistance of the IDRC, Canada. About 500 rainwater storage tanks were constructed in the Capiz Province during this project. The capacities of the tanks varied from 2 to 10 m3, and the tanks were made of wire framed ferrocement. The construction of tile tanks involved building a frame of steel reinforcing bars (rebar) and wire mesh on a sturdy reinforced concrete foundation. The tanks were then plastered both inside and outside simultaneously, which reduced their susceptibility to corrosion when compared with metal storage tanks. The Philippine rainwater harvesting system was implemented as a part of the income generating activities in the Capiz Province. Initially, loans were provided to fund the capital cost of the tanks and related agricultural operations. Under this arrangement, the project participant took a loan of $200, repayable over a three year period, and covering the cost not only of the tank but also for one or more income generating activities such as purchase and rearing of pigs costing around $25 each. Mature pigs can sell for up to $90 each, which provided an income generating opportunity that could provide sufficient income to repay me loan. This innovative mechanism for financing rural water supplies helped to avoid the type of subsidies provided by many water resources development projects in the past. (Source: Gould, 1992)

Operation and Maintenance

Maintenance is generally limited to the annual cleaning of the tank and regular inspection of the gutters and down-pipes. Maintenance typically consists of the removal of dirt, leaves and other accumulated materials. Such cleaning should take place annually before the start of the major rainfall season. However, cracks in the storage tanks can create major problems and should be repaired immediately. In the case of ground and rock catchments, additional care is required to avoid damage and contamination by people and animals, and proper fencing is required.

Level of Involvement

Various levels of governmental and community involvement in the development of rainwater harvesting technologies in different parts of Asia were noted. In Thailand and The Philippines, both governmental and household-based initiatives played key roles in expanding the use of this technology, especially in water scarce areas such as northeast Thailand.

Costs

The capital cost of rainwater harvesting systems is highly dependent on the type of catchment, conveyance and storage tank materials used. However, the cost of harvested rainwater in Asia, which varies from $0.17 to $0.37 per cubic metre of water storage (Table 10), is relatively low compared to many countries in Africa (Lee and Vissher, 1990).

Compared to deep and shallow tubewells, rainwater collection systems are more cost effective, especially if the initial investment does not include the cost of roofing materials. The initial per unit cost of rainwater storage tanks (jars) in Northeast Thailand is estimated to be about $1/l, and each tank can last for more than ten years. The reported operation and maintenance costs are negligible.

TABLE 10. Costs of Rainwater Catchment Tanks in Asia (Lee and Vissher, 1990)

System	Vol m3	Cost $	Annual Equivalent Cost $/m3	Country
Reinforced Cement Jar	2	25	0.17	Thailand
Concrete Ring	11.3	250	0.29	Thailand
Wire Framed Ferrocement	2	67	0.37	Philippines
Wire Framed Ferrocement	4	125	0.35	Philippines

Effectiveness of the Technology

The feasibility of rainwater harvesting in a particular locality is highly dependent upon the amount and intensity of rainfall. Other variables, such as catchment area and type of catchment surface, usually can be adjusted according to household needs. As rainfall is usually unevenly distributed throughout the year, rainwater collection methods can serve as only supplementary sources of household water. The viability of rainwater harvesting systems is also a function of: the quantity and quality of water available from other sources; household size and per capita water requirements; and budget available. The decision maker has to balance the total cost of the project against the available budget, including the economic benefit of conserving water supplied from other sources. Likewise, the cost of physical and environmental degradation associated with the development of available alternative sources should also be calculated and added to the economic analysis.

Assuming that rainwater harvesting has been determined to be feasible, two kinds of techniques-statistical and graphical methods-have been developed to aid in determining the size of the storage tanks. These methods are applicable for rooftop catchment systems only, and detail guidelines for design of these storage tanks can be found in Gould (1991) and Pacey and Cullis (1986, 1989).

Accounts of serious illness linked to rainwater supplies are few, suggesting that rainwater harvesting technologies are effective sources of water supply for many household purposes. It would appear that the potential for slight contamination of roof runoff from occasional bird droppings does not represent a major health risk; nevertheless, placing taps at least 10 cm above the base of the rainwater storage tanks allows any debris entering the tank to settle on the bottom, where it will not affect the quality of the stored water, provided it remains undisturbed. Ideally, storage tanks should cleaned annually, and sieves should fitted to the gutters and down-pipes to further minimize particulate contamination. A coarse sieve should be fitted in the gutter where the down-pipe is located. Such sieves are available made of plastic coated steel-wire or plastic, and may be wedged on top and/or inside gutter and near the down-pipe. It is also possible to fit a fine sieve within the down-pipe itself, but this must be removable for cleaning. A fine filter should also be fitted over the outlet of the down-pipe as the coarser sieves situated higher in the system may pass small particulates such as leaf fragments, etc. A simple and very inexpensive method is to use a small, fabric sack, which may be secured over the feed-pipe where it enters the storage tank.

If rainwater is used to supply household appliances such as the washing machine, even the tiniest particles of dirt may cause damage to the machine and the washing. To minimize the occurrence of such damage, it is advisable to install a fine filter of a type which is used in drinking water systems in the supply line upstream of the appliances. For use in wash basins or bath tubs, it is advisable to sterilise the water using a chlorine dosage pump.

Suitability

The augmentation of municipal water supplies with harvested rainwater is suited to both urban and rural areas. The construction of cement jars or provision of gutters does not require very highly skilled manpower.

Advantages

Rainwater harvesting technologies are simple to install and operate. Local people can be easily trained to implement such technologies, and construction materials are also readily available. Rainwater harvesting is convenient in the sense that it provides water at the point of consumption, and family members have full control of their own systems, which greatly reduces operation and maintenance problems. Running costs, also, are almost negligible. Water collected from roof catchments usually is of acceptable quality for domestic purposes. As it is collected using existing structures not specially constructed for the purpose, rainwater harvesting has few negative environmental impacts compared to other water supply project technologies. Although regional or other local factors can modify the local climatic conditions, rainwater can be a continuous source of water supply for both the rural and poor. Depending upon household capacity and needs, both the water collection and storage capacity may be increased as needed within the available catchment area.

Disadvantages

Disadvantages of rainwater harvesting technologies are mainly due to the limited supply and uncertainty of rainfall. Adoption of this technology requires a "bottom up" approach rather than the more usual "top down" approach employed in other water resources development projects. This may make rainwater harvesting less attractive to some governmental agencies tasked with providing water supplies in developing countries, but the mobilization of local government and NGO resources can serve the same basic role in the development of rainwater-based schemes as water resources development agencies in the larger, more traditional public water supply schemes.

Water Quality Considerations and Local People's Preferences Rain water harvesting systems, especially those sourced from rooftop catchments, can provide clean water for drinking purposes. The quality of the water, however, is largely dependent on the type of roofing materials used and the frequency of cleaning of the surface. A study carried out by Wirojanagud et al. (1989, as cited by Gould, 1992) on 189 rainwater tanks and jars in Thailand showed that only 2 of me 89 tanks sampled, and none of the 97 rainwater jars sampled, contained pathogens. Based on the results of bacterial analyses, 40% of the 189 tanks and jars sampled met the WHO drinking water standards. All of the tanks and jars sampled met me WHO standards for heavy metals, including the standards for cadmium, chromium, lead, copper and iron. In northeast Thailand, where me groundwater, the only readily available source of water, is highly saline, me local people are aware of the water quality benefits to be had by using rainwater. Before the Thai government launched me rainwater harvesting program in 1986, the local people made use of rainwater harvested from matched roofs as well as groundwater obtained from shallow tubewells. During a recent field visit to the area, the local people stated mat they were afraid of drinking water from deep tubewells, even though the groundwater abstracted from the deep tubewells was reported to be less saline and suitable for drinking water purposes. When asked, the local people mentioned that they preferred shallow tubewell water because it had a nicer taste than the water from deep tubewells; however, they preferred water from the matched roofs because of sweet taste. After the Thai government launched me rainwater harvesting program in 1986, many villagers in this region of Thailand replaced me thatched roofs with zinc sheets to increase the volume of rainwater harvested. Every house now has 6 0001 capacity jars for rainwater collection, and the jar manufacturing industry has been commercialized in the area. The demand for jars remains greater than the ability of the manufacturing firm's capacity to supply.

Cultural Acceptability

Rainwater harvesting is an accepted freshwater augmentation technology in Asia. While the bacteriological quality of rainwater collected from ground catchments is poor, that from properly maintained rooftop catchment systems, equipped with storage tanks having good covers and taps, is generally suitable for drinking, and frequently meets WHO drinking water standards. Notwithstanding, such water generally is of higher quality than most traditional, and many of improved, water sources found in the developing world. Contrary to popular beliefs, rather than becoming stale with extended storage, rainwater quality often improves as bacteria and pathogens gradually die off (Wirojanagud et al., 1989). Rooftop catchment, rainwater storage tanks can provide good quality water, clean enough for drinking, as long as the rooftop is clean, impervious, and made from non-toxic materials (lead paints and asbestos roofing materials should be avoided), and located away from over-hanging trees since birds and animals in the trees may defecate on the roof.

Further Development of the Technology

Rainwater harvesting appears to be one of the most promising alternatives for supplying freshwater in the face of increasing water scarcity and escalating demand. The pressures on rural water supplies, greater environmental impacts associated with new projects, and increased opposition from NGOs to the development of new surface water sources, as well as deteriorating water quality in surface reservoirs already constructed, constrain the ability of communities to meet the demand for freshwater from traditional sources, and present an opportunity for augmentation of water supplies using this technology.

Information Sources

Gould, J.E. 1992. Rainwater Catchment Systems for Household Water Supply, Environmental Sanitation Reviews, No. 32, ENSIC, Asian Institute of Technology, Bangkok.

Gould, J.E. and H.J. McPherson 1987. Bacteriological Quality of Rainwater in Roof and Groundwater Catchment Systems in Botswana, Water International, 12:135-138.

Nissen-Petersen, E. (1982). Rain Catchment and Water Supply in Rural Africa: A Manual. Hodder and Stoughton, Ltd., London.

Pacey, A. and A. Cullis 1989. Rainwater Harvesting: The Collection of Rainfall and Runoff in Rural Areas, WBC Print Ltd., London.

Schiller, E.J. and B. G. Latham 1987. A Comparison of Commonly Used Hydrologic Design Methods for Rainwater Collectors, Water Resources Development, 3.

UNEP [United Nations Environment Programme] 1982. Rain and Storm water Harvesting in Rural Areas, Tycooly International Publishing Ltd., Dublin.

Wall, B.H. and R.L. McCown 1989. Designing Roof Catchment Water Supply Systems Using Water Budgeting Methods, Water Resources Development, 5:11-18.

3.2 Rainwater harvesting for drinking water supply

Technical description

Rainwater has been used traditionally as the primary source of potable water in Tamilnadu (South India), with drinking water storage being provided by a construct known as an oorany. It is a very simple storage facility designed to store the locally available rainwater sufficient to meet the drinking needs of a community. Almost every village in the Ramanathapuram District has an oorany, which is an artificially constructed pond. The pond is created by excavation with the excavated soil used to form bunds around the pond. There is a sluice arrangement to admit the rainwater. The oorany is located in impermeable soils so that seepage losses are minimal, and are sized to meet the village's consumption requirements and accommodate losses such as those due to evaporation. The primary use of the stored water is for drinking, although, by enlarging the storage capacity of the oorany, irrigation requirements may also be serviced. Irrigation tanks have are common in Tamil Nadu and more so in Ramanathapuram.

The Village of Thattankudiyiruppu, in Tamilnadu State, India, is a typical community serviced by an oorany. The population of the village is 550. Accordingly, based upon the standard minimum rural drinking water requirement of 201 per capita per day, the village requires a minimum of 4 015 m³ of drinking water per year. Given that the average annual rainfall of the district is 792 mm, and employing a moderate runoff coefficient of 25%, a 2.5 ha catchment area would be needed to capture the 5 000 m³ of water used by the village. Generally, the catchment area of an oorany is closer to 5 ha, which provides additional storage to account for, inter alia, interannual variability in rainfall. The hydraulic and water quality particulars of a typical oorany are:

i)	Length at top	97.80 m
ii)	Width at top	32.60 m
iii)	Length at bottom	91.58 m
iv)	Width at bottom	26.08 m
v)	Depth	3.26 m
vi)	Capacity	9090 m3
vii)	Catchment area	6 ha
viii)	Quality of water	Potable

Extent of Use

There are as many as 39 200 oorany or rainwater storage tanks have been constructed in Tamilnadu State. The tanks cater to the needs of agriculture, and supply water to irrigations schemes that occupy nearly 30% of the irrigable lands in the State.

Operation and Maintenance

Rainwater harvesting and storage in an oorany is very simple and easy to operate. Operation and maintenance involves periodic cleaning of the oorany, as well as ensuring that the catchment area is protected water from any pollution. Constant inspection of the surrounding area is essential to prevent abuse of the water source by the people.

Level of Involvement

The entire project is a community activity with little involvement by the government. The success of the technology has already encouraged agencies like the Vivekanand Centre to support construction of drinking water oorany in other villages elsewhere in the Ramanathapuram District with a minimum degree of external assistance.

Costs

The cost of construction generally includes the provision of a draw well located outside of the ooranybunds. This abstraction point generally has a diameter of 3 In and a depth equal to the depth of the oorany. A pipe connects the well to the oorany. Additional, site-specific arrangements are made to protect the water in the oorany from pollution. An oorany with a capacity of about 10 000 m³ costs about $7 000 to construct.

Effectiveness of the Technology

This traditional method of rainwater harvesting has been extremely successful. Most communities are able to raise the capital required to fund this type of venture, and are capable of operating and maintaining the system with little assistance from the government.

Advantages

The main advantage of the method is that it is a well-tried and tested method that has been practised for a number of years. It can be implemented and maintained by communities with little external assistance. Most communities have the necessary skills within their populations, as well as the necessary mechanical equipment that may be needed to construct the pond. Generally, there is little need for chemical treatment of the rainwater. There is also no dependence on energy sources to operate the system.

Disadvantages

If not properly constructed and maintained, the oorany may be subject to seepage. Water accumulating around the pond could provide mosquito breeding habitat with a concommitant threat to the public health. In addition, if the catchment serving the oorany is not maintained, the water stored in the tank may become contaminated with particulates, faecal material and other pollutants.

Cultural Acceptability

This technology is well accepted by people because of their long tradition of using this technology.

Further Development of the Technology

The construction of the oorany could be improved by the use of new materials to better seal the berms and reduce seepage losses.

Information Sources

Kanmani, S. and K. Karmegam 1987. First Regional Seminar on Technology on Drinking Water and Related Water Management for Southern States and Union Territories, Department of Civil Engineering, Anna University, Madras.

3.3 Rooftop rainwater harvesting for domestic water supply

Technical description

Rainwater may be collected from any kind of roof. Tiled or metal roofs are easiest to use, and asbestos sheet roofs, especially when damaged, should not be used as asbestos fibres may be released into the harvested water. This technology has been used in Assam State (northeast India), where a more traditional reliable drinking water source has not been identified for a number of villages. In the State of Assam, rainwater harvesting is accomplished primarily through household rain catchment structures which are best suited for use in the villages in hilly areas, where people live in scattered huts or in small settlements. The technology also has been adopted in the neighbouring State of Meghalaya, where polythene sheet covering is used as a rooftop catchment on thatched roofs. Storage of rainwater collected from rooftop catchments is typically informal. Buckets, basins, oil drums, etc. are commonly placed under the eaves in order to store water to supplement normal water supplies. Such water is rarely used for drinking purposes.

Household rooftop rainwater collection systems consist of the following elements:

Guttering: Guttering collects the rainwater runoff from the roof and conveys the water to the downpipe. Gutters may be constructed of plain galvanised iron sheets or of local materials such as wood, bamboo, etc. All gutters should have a mild slope to avoid the formation of stagnant pools of water. Gutters with a semicircular cross-section of 60 mm radius are sufficiently large to carry away most of the intense monsoonal rainfall.

Down pipe: A vertical down pipe of 100 mm to 150 mm diameter is required to convey the harvested rainwater to the storage tank. An inlet screen (#20 wire mesh) to prevent entry of dry leaves and other debris into the down pipe should be fitted.

Foul Flush Diversion: The first flush of water from the roof is likely to contain dust, dropping and debris which has collected on the roof. This contaminated water should be diverted from the storage tank to avoid polluting the stored rainwater. Such a diversion can be achieved manually by including a ninety degree elbow on the down pipe so that the pipe can be turned away from the storage tank to divert the flow for the first 5 to 10 minutes of a storm. Alternatively, separate storage for the initial flow of rainwater may be provided in the form of a pipe with sufficient volume to contain the foul flush. Once this volume is exceeded, additional rainfall will flow into the storage tank. The contaminated water may be discharged after each heavy rain by removing a plug. Figures 6 and 7 illustrate these alternatives.

Filter: A filtering system may be placed between the down pipe, after the foul flush system, and the storage tank. Filters can be constructed using locally available materials such as sand, gravel, or charcoal, etc. placed within a container to a depth of 1.2 m. The media and the cross-sectional area of the filter should be chosen to provide a rate of filtration adequate to pass 5 to 7 In of water per hour.

Storage Tank: The size of the storage tank in a particular area should be matched to the volume of water expected to be harvested based upon the area of the roof. The volume of the tank should also be related to the quantity of water required by its users, and be appropriate in terms of cost, resources required and construction methods.

Some elements which should be considered in designing a storage tank include the following:

- An accessway with an area of about 0.25 m² (0.5 m × 0.5 m) to allow periodic cleaning of the tank.

- A double pot chlorinator of 5 1 capacity to provide continuous disinfection.

- A vent pipe and overflow pipe (fitted with screens) of 100 to 150 mm diameter to minimize the build up of gases and to allow excess water to exit the storage tank.

- An outlet pipe of 100 to 150 mm diameter located at the bottom of the tank to allow the tank to be drained for cleaning (separate from the service tap which should be located above the bottom of the tank).

- A water level indicator, in the form of graduated transparent plastic pipe for above ground tanks or float system for underground tanks, to assist the owner to gauge water use from the system.

Figure 6. Foul Flush System for Rooftop Rainwater Harvesting

Figure 7. Alternate Methods of Diverting Contaminated Runoff

Storage tanks may be constructed above ground and fitted with a self closing tap provided near the base of the tank, or underground and fitted with a hand pump, depending on the height of the house and other site specific conditions. Underground tanks should be constructed with the top 30 cm of the tank above ground level to minimize debris from the surrounding land surface being washed into the tank.

Extent of Use

This technology is widespread in the State of Assam, and is best suited for use in heavy rainfall areas.

Operation and Maintenance

The technology is simple to install and operate, and requires minimal maintenance. Maintenance consists of:

- regular cleaning of the catchment surface (i.e., the rooftop) and storage tank to avoid physical and bacteriological contamination of the rain water;

- periodic inspection of the catchment surface for leaks, especially when thatched roofs are used;

- regular cleaning of the filters to maintain good water quality and acceptable rate of filtration.

Level of Involvement

Use of this technology is primarily at the community level, with an emphasis on individual household level involvement for maintaining the technology. Assistance in designing, sizing and constructing the technology may be provided by governmental bodies such as extension services or the village panchayat in the rural areas.

Costs

The technology is highly cost-effective since it uses locally available materials for constructing the system. Capital costs are limited to the cost of gutters, down pipes, filters and storage tanks. However, all these can be constructed using low cost materials thereby reducing the overall cost of the project. The recurring costs for maintenance of the system include regular cleaning and leak prevention which can be easily undertaken by the members of the household.

Effectiveness of the Technology

If the storage tank is of a suitable size, this technology can meet the minimum standard for the supply of drinking water at a rate of 22 1 per capita per day. The harvested water is of good quality, with low turbidity and no objectionable tastes, odours and colours. The water is soft and may be slightly acidic. Bacteriologically, rainwater is generally very good and free from organic matter, but it may be contaminated by material that has accumulated on the rooftops. Wherever water quality tests have been carried out, some bacteriological contamination of water from roofs has been found. However, it is to be appreciated that a greater chance of contamination comes in the storage tanks in which the water is kept for long periods prior to consumption. As noted, storage tanks should be provided with close fitting covers, screens, and self-closing abstraction points to minimize the chance of the stored water being contaminated by materials entering the tanks after the rainwater is stored.

Advantages

The principle advantages of rooftop rainwater harvesting are:

- The capital low cost of rooftop rainwater harvesting, which is much less expensive than conventional water supply technologies.

- The ease of construction, operation and maintenance of rooftop rainwater harvesting technologies.

- The minimal operating costs, which include reduced chemical and energy costs compared to conventional water supply schemes.

Disadvantages

Disadvantages of the rooftop rainwater harvesting technology as:

- The potential for the water to be polluted by birds droppings, dust, etc., that accumulates on the rooftop requiring a regular programme of maintenance of the roof surface and filter.

- The reliance on rainfall.

Further Development of the Technology

Rooftop rainwater harvesting is generally considered to be a fully developed technology.

Information Sources

Paul, A.B. 1989. Rain and Dew as Sources of Water Supply in Assam - Some Aspects, Journal of Indian Water Works Association, Jan-March, pp 59-64.

3.4 Rainwater harvesting for agricultural water supply

Technical description

This is the most common and one of the earliest methods of rainwater harvesting used in Bangladesh. In this method, an earthen bund with a height and width of 30 to 45 cm is constructed around a field. Rainwater fills the aman created within the bund; an aman is a monsoonal paddy grown in June/July and harvested in October/November. In Bangladesh, the monsoon season begins in June/July, or some times in August if the monsoon comes late. With water stored on the field for few days, the soil softens and is suitable for preparation using ploughs drawn by animal power or power tiller. If the field retains excess water, it may be flushed out by cutting a portion of the bund. Once the land has been prepared, aman seedlings are transplanted or seeds are broadcast spread. In hilly areas, this technology can be applied in valleys between hills or wherever there is level ground on which water may be stored for few days before planting.

Figure 8. Rainwater is Stored Prior to Land Preparation

Extent of Use

All farmers whose lands are fed by harvested rainwater during the monsoons make use of this technology for preparing their lands. Farmers, by experience, have learned to match the aman crop cycle with the rainfall pattern, and the cropping cycle may be delayed by a month or so if monsoon season starts late in any particular year. This method not only softens the soil but also assists in controlling weeds by inundating organic matter and exposing weeds, crop residuals and other organic substances to aquatic decomposition processes. The organic matter is then mixed into the soil, thereby supplementing soil nutrients. Nearly all types of farms, large and small, use this process. The rainwater satisfies about 78% to 97% of the water requirements for land preparation for aman crops; the other farms, about 3% and 22% of farms, that are unable to match their cultivation with the onset of the monsoon rain, bring water from ponds or khals, rivers, wells or other waterbodies to prepare the fields for aman crops. In saline areas, harvested rainwater is used to provide agricultural water for aman paddy cropping until the river water becomes sweet. In these areas, harvested rainwater meets around 50% of water requirement for the aman crop, with the balance of the water being obtained from river sources.

Operation and Maintenance

The bunds need to be repaired every year.

Level of Involvement

This technology is implemented at the household level and requires little external involvement.

Costs

One time construction costs incurred in the creation of the bunds around an acre of land amount to six days of hired labour, or, at the 1996 wage rate of $ 1.50/day during harvesting period, about $9.00. Locally available agricultural equipment can be used for the bund construction. Annual repair costs typically involve two day of family labour per year at an equivalent cost of about $2.50. Costs per acre may be calculated at between four and five days of family labour and from three to six days of hired labour, or about $7 per season on average.

Figure 9. Excess Water is Discharged Through the Bund.

Effectiveness of the Technology

The information obtained during the field survey in Bangladesh suggests that paddy yields decline in cases where rainwater was not used to prepare the agricultural lands for planting. Declines in yields ranged from 44.8% to 51.4% of the yields obtained in fields that were prepared using this technology. To achieve similar yield as obtained with this technology, farmers would have had to incur additional expense.

Suitability

This technology is suitable for use in all flat areas with adequate rainfall.

Advantages

The technology uses locally available materials and is inexpensive to implement.

Disadvantages

The principle weakness of this technology is that it is dependent on rainfall, which may be uncertain. This may delay crop planting with consequential reductions in yield. Where there is no outlet for draining excess water from the bunded field, flooding may damage or destroy the standing crop.

Cultural Acceptability

Being a traditional technology, rainwater harvesting for agricultural supply is well accepted.

Information Sources

Mohammed Aslam, Saleh Ahmed Chowdhury, Alamgeer Faridul Hoque, and S.R. Sanwar, Intermediate Technology Group, House 32, Road 13A, Dhanmondi, Dhaka, Bangladesh, Tel. 880 2 811 934, Fax: 880 2 813 134, E-mail: [email protected].

3.5 Rainwater harvesting for irrigation water supply

Technical Description

In Bangladesh, two types of agricultural water storages are observed. One type is used to store water on plots which are slightly inclined; water accumulates in the low lying portions of the fields or in a low lying areas nearby. Water stored using this method is used for both land preparation for aman paddy cropping and during the growing/milking stage of paddy farming when the water requirement is most critical. In Bangladesh, aman is transplanted in June/July and harvested in October/November. The other type of water storage involves the storage of rainwater in ditches or depressions located outside bunds or in land depressions beside road embankments. Water is carried from these depression to the fields in buckets, pitchers or traditional dhoon whenever it is needed. In some cases, if the waterbody is large enough, water may be used to irrigate a rabi crop or for fishing during the period of monsoonal inundation. In some upland areas of Bangladesh (North Central zone), rainwater is stored in low lying plots between two hills for use in times of necessary.

Figure 10. Stagnant Water on the Lower Slope of a Plot

Rainwater stored using this technology may be transferred between fields by overflowing successive plots and may be collected in the lowest fields in a given area. In the West-Central region, rainwater is harvested from lands situated at higher elevations and conveyed to storage ponds through culverts. In this region, because farm lands are situated at lower elevations than the storage ponds, stored rainwater may also be used for irrigating farm fields during the dry season. The specific location of the catchment area and its elevation relative to the fields to be irrigated are important factors in determining the potential for using these types of rainwater harvesting technologies.

Figure 11. Irrigation of Crops with Rainwater in Upland/Hilly Areas

Extent of Use

Rainwater storage in low lying portions of farms or in neighbouring plots is possible only when the locations and elevations of the plots are suited to such storage. No detailed data on the extent of use of this technology were identified, but the field survey suggested that, if such opportunities exist, farmers made use of these technologies. In upland areas, nearly all farms having access to rainwater stored in depressions within hills made use of such water for irrigating aman paddies. In saline areas, this practice was observed on lands located within polders or embankments erected to obstruct the intrusion of saline water. In these areas, there is a conflict between aquacultural (saline water-based shrimp culture) and agricultural (freshwater-based crop) production, which has led to violent confrontations. During the field visit, the murder of a local womens' leader, named Korunamoey Sardar and aged around 40 years, allegedly by shrimp growers has caused continued deep resentment among the local farmers and has strengthened the resolve of the local people to continue fresh water cultivation within the polder in defiance of the threats by shrimp cultivators.

Operation and Maintenance

The use of natural depressions does not eliminate the maintenance requirements. Repair work, such as repairing bunds, maintaining slopes, etc. involve about two person-days of family labour per year at an equivalent cost of $2.50, based upon a rate of $1.25 per day. Local agricultural equipment is used for this purpose.

Figure 12. Irrigation of Crops with Rainwater Using Traditional Methods

Level of Involvement

This technology is implemented at the household level, although it has been implemented sometimes at the community level.

Costs

Construction costs are minimal since this system of rainwater harvesting is practised only when the land is naturally sloped, when the farmer has a plot nearby with a low enough elevation, or when there is an existing ditch or depression available where rainwater can be stored.

Effectiveness of the Technology

Data from the North Central zone of Bangladesh shows that the use of this technology increases paddy crop yields by about 32%. In order to achieve similar yields as can be achieved through irrigation using rainwater harvesting techniques, farmers would have to incur additional expenses in transporting water from other sources. The cost of transporting water would be the equivalent of five to six person-days of family labour and one to two days of hired labour.

Suitability

This technology is suitable in areas where natural depressions are found and where there is adequate rainfall to produce runoff.

Advantages

The advantages of this technology are that it is a locally implemented technology, which can be used at little additional cost.

Disadvantages

The disadvantage of this technology is that rainwater cannot be stored for long time due to seepage losses. The method also lacks scientific rigour.

Cultural Acceptability

This technology is very well accepted and has no known cultural disadvantages.

Further Development of the Technology

This is a fully developed technology. However, development of criteria for sizing storage areas would make this technique more rigorous.

Information Sources

Mohammed Aslam, Saleh Ahmed Chowdhury, Alamgeer Faridul Hoque, and S.R. Sanwar, Intermediate Technology Group, House 32, Road 13A, Dhanmondi, Dhaka, Bangladesh, Tel. 880 2 811 934, Fax: 880 2 813 134, E-mail: [email protected].

3.6 Rainwater harvesting for community water supply

Technical description

Rainwater is collected from rooftops of buildings using corrugated galvanized iron (CGI) sheets as the roofing material, a half-cut HDPE pipe gutter, and HDPE down-pipe to collect rainwater in ferrocement storage tanks. Some tanks have separate tapstands.

Figure 13. A Community-based Rainwater Harvesting System.

This technology was introduced into Nepal for the first time in 1988. As a pilot project, a 20m³ ferrocement tank was built to collect water from the roof of a middle school in the Village of Daungha. The system helped to fulfil the drinking water demand of about 300 students and teachers. The success of this community-based system, shown in Figure 13, encouraged the villagers to build more such systems, including an additional storage tank for the middle school. Two further 20m³ storage tanks were constructed to harvest rainwater from the Village Committee Office building and Primary School building in 1989.

Extent of Use

This technology is an example of a community-based rainwater harvesting system in Nepal. The example is from the Village of Daungha, in the Gulmi District in West Nepal. The interest of villagers and their active participation have helped to promote the development of such rainwater harvesting systems in Nepal, and there are currently 11 ferrocement tanks for rainwater storage in the region.

Operation and Maintenance

The following maintenance work is required in the operation of this technology:

- Regular cleaning of the rooftops and gutters: Rainwater is generally considered to be free of contamination, and, hence, it requires no treatment. Nevertheless, the roofs and gutters should be cleaned regularly to remove particulates and accumulated materials. Rainwater of the first few hours of the beginning of rainy season should not be collected in the tank, but should be used for flushing the roofs and gutters. Asbestos cement sheets and metal sheet roofing coated with lead-based paints should be avoided as they may be dangerous to health.

- Frequent cleaning of the storage tanks: The storage tank is the most expensive part of any rain water catchment system and determining the most appropriate capacity for any given locality and catchment area will critically affect both its cost and the amount of water available for supply. To ensure the longevity of the tank and quality of the water supply, regular cleaning of the tank should be carried out.

- Inspection of gutters and feeder pipes and valve chambers to detect and repair leaks: Rooftops are commonly used as catchments, even though ground catchments can provide a larger catchment areas, yield a greater volume of water to be collected, and are cheaper to construct. However, the use of ground catchments competes with agriculture for available land. Hence, in Nepal, both flat roofs, with tiles or plastered concrete leading to a floor drain, and sloped roofs are used. Sloped roofs are preferred to flat roofs because sloped roofs are accessible only for cleaning and repair purposes, and the harvested rainwater has less chance of being contaminated. Regular inspection of the drainage systems and conveyance systems minimizes water loss.

However, because this technology can be constructed and maintained locally, the Nepalese projects have been handed over to the users committees which bear the overall responsibilities for operation and maintenance of the systems. Such works as may be beyond the capacities and means of the users committees are carried out by the District Water Supply Offices.

Level of Involvement

Implementation of this technology has involved both the local communities and the government.

Costs

Based upon the experience in Nepal, the total cost of a 20 m³ water supply project, supplying 1 224 I/day, is about $24 620, or about $121 per person. Although the operation and maintenance costs of the system are negligible, the capital cost is too high for individual households and a rural community to invest independently in such a system. Thus, the cost of these community-based systems was divided between the government and community in the following ratio:

Government	$22 560
Village	$ 2060.

The cost of a 20 m³ ferrocement tank is about $2 000.

Effectiveness of the Technology

A total of 183 m³ of rainwater is collected annually in the storage tanks served by 160 m² of rooftop catchment area in the Daungha Village. Assuming that the water is used for drinking purposes only, it is estimated that about 73 m³ of water could meet the needs of the 34 residents for a year. With this system, water collected during the monsoon helps meet demand during the dry season. Of the remaining volume of water harvested, the per capita allocation of six litres per capita per day is considered to be too low to completely meet the demand for water for personal hygiene. However, the estimated 20 litres per capita per day supply for domestic use could be met from a household level 22 m³ rainfall harvesting system. Such a system would require a rooftop area of 49 m² roof area and would provide water to an average household of seven members.

Suitability

This technology is suitable for use in areas with adequate rainfall and in villages having a cluster of roofs or large buildings.

Advantages

The main advantage of having a community-based rainwater harvesting system is the time savings accrued in fetching water. This frees up time which may be utilized for other economic activities. Women, who traditionally gather water, gain more time for child care, social activities and income generating activities.

Disadvantages

The disadvantage of this technology is its high initial cost and per capita cost in small settlements.

Further Development of the Technology

While the technology may be considered to be fully developed, in order to determine the potential rainwater supply for a given catchment, reliable rainfall data (mean annual rainfall and its distribution) are required for a period of at least 20 years. Improved rainfall distribution analysis methods could enhance the utilization of this technology.

Information Sources

Contacts

I. Sainju, Civil Engineer, Department of Civil Aviation, Maintenance Branch, Tribhuvan International Airport, Kathmandu.

R. B. Tamang, Department of Civil Aviation, Repeater Station, Phulchoki, Lalitpur, Nepal.

Bibliography

Department of Water Supply and Sewerage, District Water Supply Office, Gulmi 1993. Daungha Rainwater Collection Water Supply Project, 1993, His Majesty's Government of Nepal.

Department of Water Supply and Sewerage, District Water Supply Office, Tanahu 1991. Management of Water Supply Project, 1991, His Majesty's Government of Nepal.

Gould, J.E. 1991. Rainwater Catchment Systems/or Household Water Supply, Environmental Sanitation Reviews No. 32, ENSIC, Asian Institute of Technology.

Ministry of Housing and Physical Planning and U.S. Peace Corps/Nepal 1989. Rainwater Catchment Tank Construction Technical Manual, His Majesty's Government of Nepal.

3.7 Rainwater harvesting for multiple purpose use technical description

This technology employs one of the oldest methods of rainwater harvesting in Bangladesh; namely, the use of the roof of a house to collect rainwater, and, by means of a gutter, convey the collected water to a pot for immediate use or to a storage place for later use. This system of rainwater harvesting is associated with various kinds of roofing materials including cement, corrugated iron (C.I. sheeting), thatched straw, etc. These roofing materials span the gamut of materials found within a community: cement roofed houses tend to be owned by the richer persons in a community, corrugated iron sheet roofed houses by the middle income persons, and the thatched roof houses by the poorer segments of the community. Gutters, too, are made from different materials, including corrugated iron sheets, palm wood, betel nut wood, bamboo, and banana plant leaves, etc. Storage pots are also of different types, ranging from earthen jars, locally called motkas which are of three different sizes, small, medium and large; to oil drums; to cemented tanks with steel fabricated covers. For immediate use, water is usually collected in buckets or wide-mouthed pots locally called gamlas. Sometimes, medium or large underground or above ground cement water tanks are also constructed where large quantity of water is to be stored. Rainwater from the gutters may also be stored in ditches around the house. Large earthen jars or cement storage tanks with steel plate covers are generally used by the wealthier section of the community and are semi-permanently placed inside or immediately outside of the house. In all cases, the harvested rainwater is used to meet household demand for such needs as bathing animals, washing dirty clothes, and other nonpotable purposes.

Figure 14. Rainwater Harvesting from a Corrugated Iron Roof

In the case of cement roofed houses, water storage tanks are generally constructed immediately below the roof with an opening at one side. Rainwater is directed to the storage tank by erecting a 3" to 4" brick-cement boundary. The slope is adjusted in such a way so that rainwater automatically runs into the storage tank through the opening. The opening can be closed with a steel plate cover. The boundary also has an opening which is used to bypass the storage tank and convey excess rainwater through a PVC pipe to the ground. The water from the storage tank is provided to the lower floors of the house through rubber piping, and abstracted through a plastic tap.

In the case of corrugated iron roofed houses, the corrugated iron sheets are usually inclined at angles between 30 and 40 degrees. Water collected in gutters placed at the lower edge of the corrugated iron sheeting is conveyed by gravity into motkas as shown in Figure 14. Water is supplied to the user through opening in the top of the motka which is usually kept covered.

In the case of straw roofed houses, the thatch is also generally inclined at an angle of between 30 and 40 degrees. Water running off the thatch is collected in palm wood or bamboo gutters and conveyed into motkas or buckets at the convenience of the household as shown in Figures 14 and 15. In each case, the first flush of rainwater is allowed to flow out as the storage container as it is generally very dirty. The subsequent water is stored in the motkas or other storage containers.

Figure 15. Palm Wood Guttering Used to Capture Water

Extent of Use

In places where there are chronic freshwater shortages, like Gourikhali, Kumkhali, Dacope, Ramnagar, Kaulashganj, and Shyamnagarin in the southwest of Bangladesh, rainwater obtained using roof catchments is used throughout the year for household purposes (see also the previous discussion of rainwater harvesting for domestic water supply use). Elsewhere in the southwest of Bangladesh, rainwater is used to supplement available water through January and February. In other parts of the country, rainwater is usually used for meeting immediate household needs such as bathing, feeding cows, washing clothes and dishes, etc. The stored water retains its colour and taste for about two months after the monsoon.

Figure 16. Storage Tanks

Figure 17. Storage Jars for Household and Barnyard Use.

A significant number of people living in saline areas without access to tubewells at reasonable depths or other suitable surface water sources use rainwater for drinking purposes as well as other household purposes like cooking, washing and bathing. When people do not use rainwater, it appears to be the lack of suitable storage pots or lack of knowledge of the technology for harvesting rainwater. Such persons often make use of other water sources such as ponds, which are usually contaminated. Rooftop rainwater harvesting has also been observed in hilly areas of Mymensingh District, where most middle class families were observed to use rainwater for washing and other nonpotable domestic purposes.

Operation and Maintenance

Maintenance of rainwater harvesting systems is simple, consisting of the cleaning of catchment areas, conveyance systems, and storage devices.

Level of Involvement

This technology is implemented at the household level.

Effectiveness of the Technology

Unless carefully constructed and managed, the quality of the water stored in the motkas gradually deteriorates as a result of infestation by insects and pests, settling of dust, breeding of mosquito larvae, etc. However, if the stored rainwater is filtered and the lid of the storage container tightly closed after each use, its quality can be maintained up to two months. If storage is prolonged, the stored water may acquire odours and its colour may change. Previously, local Koi, Singh or Magur fish (Anabas testudinews, Heteropreutes sp., Clarias batrachus) were used to eat the mosquito larvae and other insects. However, these fishes also discharge their own excreta into the water which degrades the quality of water. As people have become more conscious of these facts, the use offish for maintaining water quality is fast decreasing. If these fishes are grown at all, they are harvested for consumption. Currently, people sometimes use alum or other locally made flocculent aids like burnt shell to clarify the water. Water purifying tablets are very infrequently used.

Generally, the availability of a means to purify the stored water is a severe constraint to maintaining rainwater quality; usually well-to-do families practice sound preservation procedure, while to disadvantaged cannot afford to do so as they do not have motkas of an appropriate size and may lack the cash necessary to buy flocculent aids. In extreme cases, the poor use contaminated rainwater stored in inappropriate containers or use dirty pond water.

Suitability

This technology is suitable for use in areas with adequate rainfall. Costs

The capital cost of this technology is associated mainly with the purchase and installation of the gutters and storage tanks. The cost of the gutters varies depending on the type, ranging from $1.00 to $1.50 for bamboo, $4.00 to $5.00 for palm wood, and $10.00 to $15.00 for corrugated iron sheet.

Advantages

Rainwater harvesting is a relatively inexpensive and popular technology.

Disadvantages

Disadvantages of harvesting rainwater include contamination by pollutants from the roof mixing with the water, and degradation of the stored water due to contamination by toads, mosquitos, cockroaches, etc.

Cultural Acceptability

There are no known problems associated with the use of this technology.

Further Development of the Technology

HEED-Bangladesh, an NGO located in Dacope, stores water in a fibre glass tank pumped by centrifugal pump from a nearby rainwater pond. Water tanks could also used in conjunction with such a pumping system to store rainwater on the rooftop.

Information Sources

Mohammed Aslam, Saleh Ahmed Chowdhury, Alamgeer Faridul Hoque, and S.R. Sanwar, Intermediate Technology Group, House 32, Road 13A, Dhanmondi, Dhaka, Bangladesh, Tel. 880 2 811 934, Fax: 880 2 813 134, E-mail: [email protected].

3.8 Open sky rainwater harvesting technical description

The open sky rainwater catchment is the least sophisticated form of rainwater harvesting, requiring minimal levels of investment to install, maintain and operate. For this reason, open sky rainwater harvesting is usually practised by relatively poor people who cannot afford appropriately-sized gutters or motkas in which to store water, In Bangladesh, a number of variants on this technology have been observed, ranging in cost and design from two corrugated iron sheets supported by four bamboo posts and slanted in such a way as to collect and direct rainwater into pots, motkas, etc., to plastic sheeting, suspended on four bamboo sticks, with an hole in the centre, weighted with a brick chip, to direct rainwater into a pot placed below the hole, as shown in Figure 18. When applied for agricultural use, the polyethylene sheeting may be placed in the open and slanted so that rainwater collecting on the plastic flows off the sheeting and downslope to the agricultural. Mosquito nets, bed sheets or even sarees (women's garments), inverted umbrellas, and open drums have been used as catchments to harvest rainwater, while fishermen and mariners living offshore for a considerable periods have traditionally harvested rainfall to replenish potable water supplies on their boats.

Figure 18. Open sky rainwater harvesting using of plastic sheeting in Shamnagar.

Operation and Maintenance

This technology requires little maintenance, except that devoted to the periodic cleaning of water storage pots, and few skills to operate.

Level of Involvement

This technology may be implemented at the household level.

Costs

Use of this technology can be had for a minimal investment in materials. In its relatively sophisticated version, that constructed of corrugated iron sheeting, typical costs would be between $5 and $9 for two corrugated iron sheets. In its least expensive form, that constructed of plastic sheeting, the cost would be about $0.50. Likewise, the cost of storing the harvested rainwater depends on the type of storage vessel used. Typical costs would range from about $0.25 to over $500: pitchers would cost about $0.25 each; small earthen jars (motkas), $1.20; medium-sized earthen jars, $5.00; large earthen jars, $10.00; cement underground storage tanks, $50 to $500; and, cement above ground storage tanks, $100 to $300.

Effectiveness of the Technology

This technology is effective in meeting the short term water requirements of people living in boats and of small families lacking access to other water supplies.

Suitability

This technology is limited to very small scale uses.

Advantages

This technology is simple to use, requiring few skills and minimal materials.

Disadvantages

It may be difficult to securely anchor the rainwater catchment materials during windy conditions or during storms, limiting the ability of the technology to harvest rainwater. Because of the limited surface area of the rainwater catchment, this technology does not provide a reliable source of water, and its use is restricted to the wet season.

Figure 19. Woman taking fresh water from a pond on Hatya Island.

Cultural Acceptability

There are no known cultural problems associated with the use of this technology.

Information Sources

Mohammed Aslam, Saleh Ahmed Chowdhury, Alamgeer Faridul Hoque, and S.R. Sanwar, Intermediate Technology Group, House 32, Road 13A, Dhanmondi, Dhaka, Bangladesh, Tel. 880 2 811 934, Fax: 880 2813 134, E-mail: [email protected].

3.9 Rainwater harvesting in ponds

Technical description

In the southern region of Bangladesh, the salinity of both surface and ground waters is beyond the tolerable limits for human and agricultural uses, including watering of animals as well as plants. From time immemorial, pond water, replenished by rainfall, is used for drinking and other purposes, including for fish cultivation. The ponds are specially constructed with bunds so that surface water cannot enter the ponds. This feature keeps the bed of the pond relatively free of sediment. Traditionally, trees have been planted on all four sides of the ponds to provide additional protection of the pond area. In the Sunderban region, animals are permitted to drink from the ponds during the night.

Extent of Use

In southern portion of Hatya Island (Figure 18), and other remote islands in the Bay of Bengal, rainwater, collected in ponds, meets nearly 80% of the drinking water requirements during the monsoon season. The water levels in the ponds fall during the dry season, and the water becomes turbid and more saline due to the deposition of marine aerosols, but the water continues to be used by the local people who have no other source of water, although some households bring water from distant areas. The pond water is used for bathing, washing of clothes and other household purposes through out the year. Where tubewells exist, women are generally carry the water from the wells to the point of use. In contrast, even in areas where religious norms are strictly adhered to, men may be found to carry water from the ponds.

Operation and Maintenance

Maintenance of the ponds involves repairing the bunds, cleaning and removing sediment, and general upkeep of the surrounding area.

Level of Involvement

This technology is generally implemented at the community level.

Costs

Capital costs depend on the materials and methods used in constructing and lining the ponds. Typical pond construction costs range between $350 and $500 for a 15m x 15m pond. Maintenance costs are typically about $12 per year.

Effectiveness of the Technology

In Bangladesh, the ponds fill with rainwater during the monsoon season, which, on Hatya Island, extends from April to August. At the conclusion of the monsoons, the water level in the ponds falls rapidly during January and February, and the water becomes salty. Nevertheless, a large number of people depend on the ponds for their domestic water supply. Hence, this technology appears to be very effective in meeting local needs.

Suitability

This technology is suitable in areas with abundant rainfall to fill the ponds naturally.

Advantages

This technology is relatively inexpensive and can be implemented using local technological skills and community cooperation.

Disadvantages

There is a potential for the pollution of the pond water by animals. Also, if the ponds are poorly maintained, there may be seepage losses. Because the ponds are open, they are subject to evaporative losses.

Cultural Acceptability

Some communities do not drink water from this type of storage pond because it is considered unholy and contaminated.

Further Development of the Technology

This technology may be considered to be fully developed. However, cost effective methods need to be introduced to reduce water losses and pollution to improve its effectiveness.

Information Sources

Mohammed Aslam, Saleh Ahmed Chowdhury, Alamgeer Faridul Hoque, and S.R. Sanwar, Intermediate Technology Group, House 32, Road 13A, Dhanmondi, Dhaka, Bangladesh, Tel. 880 2 811 934, Fax: 880 2 813 134, E-mail: [email protected].

3.10 Artificial recharge of groundwater technical description

Artificial recharge is the planned, human activity of augmenting the amount of groundwater available through works designed to increase the natural replenishment or percolation of surface waters into the groundwater aquifers, resulting in a corresponding increase in the amount of groundwater available for abstraction. Although the primary objective of this technology is to preserve or enhance groundwater resources, artificial recharge has been used for many other beneficial purposes. Some of these purposes include conservation or disposal of floodwaters, control of saltwater intrusion, storage of water to reduce pumping and piping costs, temporary regulation of groundwater abstraction, and water quality improvement by removal of suspended solids by filtration through the ground or by dilution by mixing with naturally-occurring groundwaters (Asano, 1985). Artificial recharge also has application in wastewater disposal, waste treatment, secondary oil recovery, prevention of land subsidence, storage of freshwater within saline aquifers, crop development, and streamflow augmentation (Oaksford, 1985).

A variety of methods have been developed and applied to artificially recharge groundwater reservoirs in various parts of the world. Details of these methods, as well as related topics, can be found in the literature (e.g., Todd, 1980; Huisman and Olsthoorn, 1983; Asano, 1985; CGWB, 1994). The methods may be generally classified in the following four categories (Oaksford, 1985):

(1) Direct Surface Recharge Technique (ASANO, 1985).

(2) Direct Subsurface Recharge Technique.

(3) Combination surface-subsurface methods, including subsurface drainage (collectors with wells), basins with pits, shafts, and wells.

(4) Indirect Recharge Techniques.

Direct surface recharge techniques are among the simplest and most widely applied methods. In this method, water moves from the land surface to the aquifer by means of percolation through the soil. Most of the existing large scale artificial recharge schemes in western countries make use of this technique which typically employs infiltration basins to enhance the natural percolation of water into the subsurface (Dewan Mohamed et al., 1983). Field studies of spreading techniques have shown that, of the many factors governing the amount of water that will enter the aquifer, the area of recharge and length of time that water is in contact with soil are the most important (Todd, 1980). In general, these methods have relatively low construction costs and are easy to operate and maintain.

Direct subsurface recharge techniques convey water directly into an aquifer. In all the methods of subsurface recharge, the quality of the recharged water is of primary concern. Recharged water enters the aquifer without the filtration and oxidation that occurs when water percolates naturally through the unsaturated zone. Direct subsurface recharge methods access deeper aquifers and require less land than the direct surface recharge methods, but are more expensive to construct and maintain. Recharge wells, commonly called injection wells, are generally used to replenish groundwater when aquifers are deep and separated from the land surface by materials of low permeability. All the subsurface methods are susceptible to clogging by suspended solids, biological activity or chemical impurities. Recharge wells have been used to dispose of treated industrial wastewaters, to add freshwater to coastal aquifers experiencing saltwater intrusion, and to force water under pressure into permeable bedrock aquifers to arrest land subsidence resulting from extensive withdrawals of groundwater, although with variable success (CGWB, 1994). In many places, including the United States, Japan and Thailand, the use of injection wells is still considered experimental (Dewan Mohamed et al., 1983).

Combinations of several direct surface and subsurface techniques can be used in conjunction with one another to meet specific recharge needs.

Indirect methods of artificial recharge include the installation of groundwater pumping facilities or infiltration galleries near hydraulically-connected surface waterbodies (such as streams or lakes) to lower groundwater levels and induce infiltration elsewhere in the drainage basin, and modification of aquifers or construction of new aquifers to enhance or create groundwater reserves. The effectiveness of the former, induced recharge method depends upon the number and proximity of surface waterbodies, the hydraulic conductivity (or transmissivity) of the aquifer, the area and permeability of the streambed or lake bottom, and the hydraulic gradient created by pumping. Using the latter technique, aquifers can be modified by structures that impede groundwater outflow or that create additional storage capacity. Groundwater barriers or dams have been built within river beds in many places, including India, to obstruct and detain groundwater flows so as to sustain the storage capacity of the aquifer and meet water demands during periods of greatest need. Construction of complete small-scale aquifers also seems feasible (Helweg and Smith, 1978). Notwithstanding, indirect methods generally provide less control over the quantity and quality of the water than do the direct methods.

Extent of Use

The concept of artificial recharge has been known for a long time. The practice began in Europe during the early nineteenth century. However, the practice has rarely been adopted on a large scale, with most large scale applications being found in countries such as the Netherlands, Germany, and USA (Dewan Mohamed et al., 1983). Israel transports 300 million cubic metres of water annually from north to south through the National Water Carrier System and stores two-thirds of it underground (Ambroggi, 1977). The water is used to meet high summer demands and offers a reliable source of supply during dry years. On the North Plain of China, which is prone to droughts, water from nearby streams is diverted into underground storage areas with capacities of about 500 million cubic metres. Several counties in Hebei Province are using artificially recharged aquifers to combat sinking water tables (Widstrand, 1978). In India, subsurface storage has caught on as a way of providing a reliable source of irrigation water. A number of artificial recharge projects have been carried out in that country (CGWB, 1994) (see Case Studies, Chapter 5).

Operation and Maintenance

To ensure the effective and efficient operation of an artificial recharge system, a thorough and detailed hydrogeological study must be conducted before selecting the site and method of recharge. In particular, the following basic factors should be considered: the locations of geologic and hydraulic boundaries; the transmissivity, depth to the aquifer and lithology, storage capacity, porosity, hydraulic conductivity, and natural inflow and outflow of water to the aquifer; the availability of land, surrounding land use and topography; the quality and quantity of water to be recharged; the economic and legal aspects governing recharge; and the level of public acceptance.

Level of Involvement

Because of the technical complexity involved in siting and regulating artificial recharge, this technology is generally implemented at the governmental level.

Costs

Rushton and Phadtare (1989) describe artificial recharge pilot projects in both alluvial and limestone aquifers in Mehsana area of Gujarat, India. Recharge was accomplished using spreading channels, percolation tanks and injection wells. Table 11 presents a summary of the initial and operational costs for the various schemes. The most expensive scheme, an injection well feeding an alluvial aquifer, had initial and operating costs per unit volume of recharged water of $100/m³.

TABLE 11. Costs of Various Artificial Recharge Schemes in India ($/m³).

Artificial Recharge Structure	Initial Cost	Running Cost
Injection well (alluvial area)	100	100
Spreading Channel (alluvial area)	9	10
Percolation Tank (alluvial area)	2	7
Injection well (limestone area)	6	21
Spreading Channel (limestone area)	7	6

It is apparent from Table 11 that injection wells in hard rock areas are less expensive since they tend to be shallower and have a lesser risks of clogging. Percolation tanks appeared to be least expensive in terms of initial construction costs; this would be the case in areas where the tanks already exist. In such cases, the initial cost only involves the cleaning of the bed of the tank. For economic reasons, the main uses of artificially recharged water are likely to be providing water for domestic needs, industry and environmental conservation. Because of its relatively high cost, recharged water is not generally suited for irrigation for a total crop, but it can be used to provide supplemental irrigation water for rain-fed crops or to provide additional water to crops at a crucial growth stage during periods of water shortage. As a general rule in this regard, groundwater must be efficiently used and effectively applied such that the net benefits from its use are maximized over time. Guidelines for the socio-economic and financial appraisal of artificial recharge projects in developing countries, necessary to assess these net benefits, are provided by CGWB (1994).

Suitability

Groundwater recharge methods are suitable for use in areas where aquifers exist. Typically, unconfined aquifers are recharged by surface injection methods, whereas confined aquifers are generally recharged through subsurface injection. Surface injection methods require relatively flat or gently sloping lands, while topography has little effect on subsurface recharge methods. Aquifers best suited for artificial recharge are those which can absorb and retain large quantities of water. In temperate humid climates, the alluvial areas which are best suited to artificial recharge are areas of ancient alluvium, the buried fossil river-beds and interlinked alluvial fans of their main valley and tributaries. In the arid zone, recent river alluvium may be more favourable than in humid zones. In these areas, the water table is subject to pronounced natural fluctuations. Surface recharge methods are best suited to these cases. Coastal dunes and deltaic areas are also often very favourable areas for artificial recharge schemes. Dense urban and industrial concentrations in such areas may render artificial recharge schemes desirable, generally using subsurface recharge wells to inject surface water into the aquifers.

When the quantity and availability of recharge water is highly variable, such as in an intermittent stream, any of the surface application methods are suitable. Basin and pit techniques have the greatest advantages because they can be designed to accommodate expected flood flows. In contrast, shafts and wells have little storage capacity and, therefore, require a more uniform supply of water. Indirect methods, such as induced recharge, are virtually unaffected by changes in surface water flows because the rate of recharge is controlled by extraction rates (Oaksford, 1985).

The physical, chemical and biological quality of recharge water also affects the selection of recharge method. If suspended solids are present, surface application techniques tend to be more efficient than subsurface techniques where they can result in clogging of injection wells. It is also important that the recharge water be chemically compatible with the aquifer material though which it flows and the naturally occurring groundwater to avoid chemical reactions that would reduce aquifer porosity and recharge capacity. Toxic substances must not be present in the recharge water unless they can be removed by pretreatment or chemically decomposed by a suitable land or aquifer treatment system. Similarly, biological agents, such as algae and bacteria, can cause clogging of infiltration surfaces and wells, limiting the subsequent use of the recharged water.

Effectiveness of the Technology

Various artificial recharge experiments have been carried out in India by different organizations, and have established the technical feasibility of the artificial recharge of unconfined, semi-confined and confined aquifer systems. However, the most important, and somewhat elusive, issue in determining the utility of this technology is the economic and institutional aspects of artificial groundwater recharge. Experiences with full-scale artificial recharge operations in India and elsewhere in Asia are limited. As a consequence, cost information from such operations is incomplete. The available data, from certain hydrological environs in which recharge experiments have been initiated and/or are in progress, suggest that the cost of groundwater recharge can vary substantially. These costs are a function of availability of source water, conveyance facilities, civil constructions, land, and groundwater pumping and monitoring facilities (CGWB, 1994).

Advantages

As surface water augmentation methods, such as dams and diversions, have become more expensive and less promising in terms of environmental considerations, the prospects of storing surplus surface water underground and abstracting it whenever and wherever necessary appears to be more effective technology. In urban areas, artificial recharge can maintain groundwater levels in situations where natural recharge has become severely reduced.

Disadvantages

There are a number of problems associated with the use of artificial recharge techniques. These include disadvantages related to aspects such as recovery efficiency (e.g., not all of the added water may be recoverable), cost effectiveness, contamination risks due to injection of recharge water of poor quality, clogging of aquifers, and a lack of knowledge about the long term implications of the recharge process. Hence, careful consideration should be given to the selection of an appropriate site for artificial recharge in a specific area.

Cultural Acceptability

Cultural considerations, stemming from socio-economic concerns, often enter into the selection of a recharge method and site. The availability of land, land uses in adjacent areas, public attitudes, and legal requirements generally play a role in defining the acceptability of artificial recharge in a given setting, In urban areas, where land availability, costs and uses in adjacent areas may pose restrictions, injection wells, shafts or small pits requiring highly controlled water supplies and little land area may be preferable to larger scale, surface spreading recharge methods. Surface recharge facilities generally require protected property boundaries, regular maintenance, and continuous surveillance if they are to be acceptable to the public.

Further Development of the Technology

The recharge process is extremely complex, and, due to the numerous factors affecting the process, is only partly understood. The studies on artificial recharge techniques are mostly site-specific and descriptive in nature, which gives little insight into the potential success of implementing this technology in other locations. Thus, there is a need for further research and development of artificial recharge techniques for a variety of conditions. In addition, the economic, managerial and institutional aspects of artificial recharge projects need to be studied further.

Information Sources

Contacts

Professor Ashim Das Gupta, Water Engineering and Management Program, Asian Institute of Technology, Post Office Box 4, Klong Luang, Pathumthani, Bangkok, Thailand, Tel. 66 2 516 0110, Fax: 66 2 516 21 26, E-mail: [email protected].

Bibliography

Ambroggi, R.P. 1977. Underground Reservoirs to Control the Water Cycle, Scientific American, 236(5):21-27.

Asano, T. 1985. Artificial Recharge of Groundwater. Butterworth Publishers, Boston, 767 pp.

CGWB (Central Ground Water Board) 1994. Manual on Artificial Recharge of Ground Water. Technical Series-M, No. 3. Ministry of Water Resources, Government of India, 215 pp.

Helweg, O.J. and G. Smith 1978. Appropriate Technology for Artificial Aquifers. Groundwater, 16(3): 144-148.

Huisman, L. and T.N. Olsthoorn 1983. Artificial Groundwater Recharge. Pitman Publishing Inc., Massachusetts, 320 pp.

Oaksford, E.T. 1985. Artificial Recharge: Methods, Hydraulics, and Monitoring, In: Artificial Recharge of Groundwater, T. Asamo, editor. Butterworth Publishers, Boston, pp. 69-127.

Rushton, K.R. and P.N. Phadtare 1989. Artificial Recharge Pilot Projects in Gujarat, India, In: Groundwater Management: Quantity and Quality, IAHS Publication No. 188, pp. 533-545.

Todd, D.K. 1980. Groundwater Hydrology. Second Edition. John Wiley & Sons, New York, 535 pp.

Widstrand, C. (Editor) 1978. The Social and Ecological Effects of Water Development in Developing Countries. Pergamon Press, New York.

3.11 Fog, dew and snow harvesting

Technical description

Fog and dew are forms of precipitation, and, by helping to maintain high humidity, limit evaporation from the soil and transpiration from vegetation. Due to fine size of fog droplets (diameters range from about 1 Tm to 40 Tm), and their low velocity of descent (ranging from 1 cm/s to approximately 5 cm/s), moisture is carried readily by breezes of even low velocity. Hence, fog harvesting requires a nearly vertical surface as catchment area for its collection. In contrast, dew harvesting requires an horizontal surface. A gravel layer is commonly used in agricultural areas as a means of maintaining soil moisture by dew harvesting, while minimizing evaporative losses and increasing soil temperature. In the evening, the gravel layer cools and remains cool in the early morning, when water vapour condenses onto the gravel creating droplets which pass between the gravel particles and reach the soil surface, moistening the soil.

Snow, being another form of precipitation, can also be harvested to provide an alternative supply of freshwater. Snow harvesting requires the construction of a pit, generally ranging in size from about 6 to 8 metres in diameter and about 10 metres in depth. The pit is heavily compacted and the collected snow is dumped into the pit to a depth of 2 to 3 metres. The compacted snow is covered with earth, which acts as an insulator, and a bamboo tube is placed about 50 cm above the base of the pit to serve as an outlet. As the snow melts around the bamboo pipe, water trickles along the bamboo and into a pot placed beneath the outlet. The water collected in the pot may be used for household drinking water and can supply water to up to 14 families (UNEP, 1982).

Extent of Use

Fog and dew harvesting is practised in Gansu Province, in northwest China, where melons are cultivated with water supplied using dew harvesting techniques. The melons are cultivated in soil beds covered with a 10 cm to 15 cm thick layer of gravel. The pieces of gravel range from 2 cm to 5 cm in diameter, and have proven to be a satisfactory growing medium for melons. These farms are well known as the 'gravel fields for melons' in China (UNEP, 1982).

Applications of the traditional snow harvesting technology to augment drinking water supplies can be found in Takhar Province, Afghanistan.

Operation and Maintenance

The technologies for harvesting alternative forms of atmospheric moisture tend to be based upon simple precepts and are traditional freshwater augmentation techniques.

Level of Involvement

These technologies are generally implemented at the household and small community levels.

Costs

No cost data were available, but costs may be assumed to be negligible as the technologies make use of commonly available materials and implements.

Effectiveness of the Technology

Studies have shown that about 10 l/m²/day of fog-derived water can be collected from the vertical section of a tree. In the Dhofar region of southern Oman, water from fog was collected for 79 days at an average rate of 860 l/day. Thus, fog and dew harvesting technologies may be effective in supplying small volumes of water for specific, supplemental uses.

Suitability

These technologies are generally suitable for use in mountainous regions, where fogs are common and snowfalls occur.

Advantages

These traditional technologies are inexpensive and simple to implement.

Disadvantages

Fog and dew harvesting technologies do not utilize a reliable source of water; the occurrence of fogs, especially, is uncertain, although certain areas do have a known propensity for fog development (particularly, mountainous coastal areas on the western continental margin). Further, calculation of even an approximate quantity of water that can be obtained at a particular location is difficult (Schemenauer and Cereceda, 1994).

Cultural Acceptability

There are no known problems associated with the use of water harvested from fog, dew and snow.

Further Development of the Technology

A great deal of further research and experience with pilot scale projects is needed before these technologies can be considered to be fully developed.

Information Sources

Schemenaur, R.S. and P. Cerceda 1994. Fog Collections Role in Water Planning for Developing Countries, Natural Resources Forum, Vol. 18.

UNEP (United Nations Environment Programme) 1982. Rain and Storm water Harvesting in Rural Areas, Tycooly International Publishing Ltd. Dublin.

3.12 Bamboo pipe water supply system

Technical description

In some villages in the hills of Nepal, drinking water is supplied to consumers through a bamboo piping system. In Barbotey Village, in the Dam District of Nepal, for example, water is supplied to two households (12 people) from a common source. A longitudinally cut bamboo tube, semi-circular in cross-section, serves as an intake. Water, drawn from the source, flow along about 100 In of open channel bamboo piping to a bamboo tap. Water flows by gravity down a 1% slope that follows the ground profile. The bamboo pipes, supports and ancillary plumbing fixtures are made from bamboo stems cut from the nearby forests.

The raw bamboo is cut in half to form a semi-circular pipe, and laid on the top of bamboo supports that carry the pipe down the slope to the consumers. At each change in direction (i.e., at the bends), the pipe is braced and supported by bamboo itself. At each socket joint, two bamboo lengths overlap and are again supported by bamboo bracing. At the bamboo tap, a bamboo inlet is inserted from the top and water is withdrawn hole at the bottom. A small HDPE pipe is also used in building the tap. This system is completely based on local technology using local materials.

Extent of Use

Bamboo conveyance systems are used throughout the hilly areas of the eastern region of Nepal.

Operation and Maintenance

Because bamboo decays as a result of its exposure to the weather and the scouring effect of the flowing water, all of the bamboo components have to be replaced each year. Thus, the annual operation and maintenance costs are the same as the capital cost, about $4.60 per year.

At present, two households have been operating and maintaining the system. They frequently visit the line to remove debris so that water flows smoothly. Surplus water is used for kitchen garden watering purposes. More than 50% of the water entering the system is lost due to leakage during the passage of the water from the source to the tap.

Level of Involvement

These distribution schemes may be implemented at the local community level, by the local users themselves. New techniques to improve the system have not been implemented, and the users are waiting for this scheme to be replaced by a piped water system. Nevertheless, there are some measures which could be considered fin order to improve the bamboo distribution system and the government could promote this technology in other areas where bamboo is commonly available.

Costs

The cost of the scheme is very low, as it only uses local materials. Total cost is about $4.60, and is incurred annually in the replacement of the bamboo.

Effectiveness of the Technology

At present, the system provides 0.201 per person of drinking water in the wet season. This volume diminishes to 10% of the wet season volume during the dry season. The system eliminated the need for the women of the households served to walk long distances to fetch water.

Suitability

This technology is suitable in areas with a good natural source of water nearby, a steep topography, and a ready source of natural piping materials.

Advantages

This technology is simple and uses local materials. Therefore, it is very cheap and can be implemented at the local level without skilled labour or specialised materials and equipment.

Disadvantages

Since the bamboo piping is simply placed on top of the framework that supports the pipeline, high winds or broken branches can displace the piping and cause the system to break down. Further, because the pipeline is open, the chances of dirt, debris and tree leaves falling into, and contaminating, the water are extremely high. This potential for contamination requires that users screen and boil the water before they use it for drinking purposes.

Further Development of the Technology

This technology could be improved through the development of means to ensure that (i) the bamboo pipe is free from debris and contaminants, (ii) there is a continuous flow of water to minimize the rate of decay of the bamboo (bamboo left without water for more than 60 days decays rapidly), and (iii) there is provision for chlorination (at a rate of 10 mg/l chlorine) to improve water quality as well as preserve the bamboo from decay. Some improvements in this technology which have already been identified include the use of a fully enclosed bamboo pipe and plastic pipe joints between tube segments to control water loss due to evaporation and spillage. The use of fully enclosed bamboo tubes is impeded somewhat by the intemodes which grow naturally across the bamboo stem at intervals of about 1 m. These must be removed by drilling, adding a degree of complexity to the technology (the drilling can be accomplished using an hand auger attached to a steel bar, manually inserted into the bamboo tube from both the ends). Also joining the bamboo stems with polyethylene pipe of an appropriate size can control leakage through the joints. Bamboo pipes also can be reinforced with 3 mm diameter galvanized wire, which can also be used to anchor the pipeline to the supporting structures. In some situations, the pipe can be laid underground, but problems may arise due to the presence of fungi and termites. Applications of insecticides and anti-fungal agents can be applied to the trenches to control these pests, but at the increased risk of contamination of the supply.

Information Sources

Amar Neku, Engineer, District Water Supply Office, Dam District, Mechi Zone, Nepal.

3.13 Hydraulic ram technical description

Hydraulic ram technology uses the power of falling water to force a small portion of the water to a height higher than that of the source. The ram operates according to well-known hydraulic principles, with the total force required to elevate a given volume of water being that which is greater than the sum of the forces created by the vertical distance which the water has to be elevated (or the static head) and the resistance offered to the flow within the suction and delivery pipes (or the friction head). In the Village of Baugha Ghuma in the Palpa District of Nepal, the source of water is a small stream, Bhulke Khola, having a dry season flow of about 8 l/sec (500l/min), located about 1.5 km downhill from the village. The bed of the river at the point of abstraction is concreted (30 In length by 3 In width). A weir diverts a portion of the river flow to a stone masonry intake, which is fitted with two square outlet structures at the bottom. Each square hole serves as an anchor point for a bundle of four 63 mm diameter HDPE pipes, which feed into two 200 mm diameter vertical rolled steel stand pipes, each 5 m in height. Two 7.6 cm galvanized iron pipes, 60 m in length, connect to the vertical stand pipes and form the driver pipes which are directly joined to the ram pump body. The ram pump body is fitted with two impulse valves, one allowing water to flow to waste and one allowing water to flow to the delivery system. Two 10 cm diameter ram pump sets are housed in a pump house. The pumps have a working head of 20 m and a delivery head of 185 m.

Water is abstracted from the river at the weir and is delivered to the pumps by the driver pipes. The driver pipes are angled at 11.3°, providing water to the pumps at a rate of 4.5 l/sec (27 l/min). Water flows through the pump body until such time as the overflow impulse valve is forced closed by the water pressure. The sudden cessation of flow through the overflow impulse valve forces the water through the second impulse or delivery valve, directing the water into an air chamber, which, in turn, forces a portion of the flow to be propelled upward through the delivery pipes into a 2 m³ storage tank. This releases the pressure in the air tank, causing the delivery valve to reseal and again directing the flow through the overflow until such time as the overflow impulse valve is forced closed by the water pressure. The daily output of this pumping system is 39 0001, which is dispensed through taps serving 14 households within a 2 400 In distribution system (consisting of 1 600 m of 50 mm diameter HDPE pipe and 800 m of 40 mm diameter HDPE pipe) at a rate of 0.45 l/sec.

Operation and Maintenance

To prepare the pump for operation, the valves at the source must be open so that water fills the drive pipe and pump body. When the pump body tank has been filled for several minutes and all the air bubbles have been removed from the drive pipe, the pump is ready to start. If air bubbles remain in the drive pipe, the impulse valves will not function. The impulse valves open and close automatically. (As described above, water runs down through the drive pipe, going faster and faster until it forces the overflow impulse or clack valve to close suddenly. The weight of the moving water suddenly stopped creates a very high pressure and forces some of water past a non-return or delivery valve into an air chamber, compressing the air more and more until the energy of the moving water is spent. This compressed air acts as a spring and forces the water in a steady stream up the delivery pipe into the storage tank.)

The pump has been developed with the intention that it should run for one year without replacement of any parts. The parts that generally need replacement are the rubber seals in the two valves and the rubber ring gaskets in the flanges of each pump. The rubber seal ring is the rubber piece which seals the overflow impulse and the delivery impulse valves. No special tools are required for the ordinary operation of the pump; the tools required for periodic pump repair are two ring spanners, two open spanners and two pipe wrenches. In actual practice, the system is prone to malfunction due to the failure of the pump and, consequently, the villagers have to rely on other small-scale water systems, although these alternate systems are quite often inadequate. The main cause of system malfunction is wear and tear on the rubber seals and gaskets, and the valve rods.

A good system is adopted to control the distribution of water from the taps. An operator from each ward, identified by the Village Water User's Committee, distributes water starting at 05:00. Each household gets about 45 litres. To minimize waste, a small pond is usually created in the area of the tapstands to collect water spilled at the tapstands and the rainwater. The water collected in the pond is used for washing utensils, bathing and watering cattle.

Level of Involvement

The technology was introduced by the United Mission to Nepal (UMN) with technical assistance provided by the Butwal Technical Institute, Nepal. An high level of community participation has been involved in implementing the technology. The success of the project has been due to the initiatives of the Village Water User's Committee, which has collected funds for, and promptly carried out, necessary repair works when failures occurred. (Unfortunately, there appeared to be no regularity in the collection of maintenance funds which limits the ability of the Committee to engage in preventive maintenance.)

Costs

The total cost of the project is $20 000. Maintenance and repair costs are somewhat in excess of $80.

Effectiveness of the Technology

The system supplies water to 14 households (about 100 people), and has been effective in reducing the time and effort formerly devoted to fetching water from the river.

Suitability

The technology can be introduced in areas where there is an abundance of water located at a source some distance below the settlement. It can be used in situations where there is no electricity to operate electrically-driven pumps. Depending on the source, the water can be used for drinking as well as irrigation purposes

Advantages

The advantage of this technology is its simplicity and lack of energy costs involved in pumping water.

Disadvantages

The disadvantage of this system is its irregularity, which is due to the lack of availability of spare parts and skilled manpower, rather than technical problems.

Further Development of the Technology

There are plans to implement further water supply projects in other districts of the eastern part of Nepal based upon this technology, which may be considered to be fully developed. However, for such systems to be successful, the local people must be trained to operate maintain the mechanism of the ram pump.

Information Sources

Friesen, R.M., J.F. Rollins, and Govinda Devkota. s.d. Hydraulic Ram Pump Hand Book. Butwal Technical Institute, Butwal, Nepal.

3.14 Development and protection of natural springs

Technical description

The main objective of spring development and protection is to provide improved water quantity and quality for human consumption. Development of natural springs tends to improve their yield, in contrast to the generally-held belief that discharges decline if the springs are touched. Spring development activities include provision of storage tanks, tapstands, drainage, and catchment area protection. Thus, the design of a standard spring development and protection scheme includes the construction of an intake structure, collection tank, tapstand, and retaining wall, and the provision of drainage, fencing and grassed surround.

The intake structure is located at the source of the spring (called the eye, or the point within the spring where the spring flow is concentrated and follows a stable channel), and collects the water for transfer to the collection tank. The intake structure also protects the eye of the spring from immediate and future contamination. In concentrated springs, where the water appears in a single channel, water can be tapped easily using a standard catchment structure at the eye. In dispersed springs, where the water flow is diffused and an eye is not discernable, suitable channels may need to be constructed to divert water from diffused sources to the catchment area. A typical intake structure is constructed of a minimum of 2 In backfill above the source of the spring. In of which should be constructed of impervious clayey soil. This construct is protected from erosion by a dry stone retaining wall built to prevent the backfill area from being washed away. Immediately around the spring is constructed a filter bed of dry rubble. In dispersed springs, where the construction of a filter bed may not be possible, a dry-stone channel may be used to the direct water from the spring source to the catchment floor. The stone channel and catchment area are covered with heavy duty plastic sheets to stop the surface water from mixing with the spring water. A concrete pad is required below the filter bed whenever the soil conditions are in doubt. However, it is important to ensure that the concrete pad of the intake structure floor and walls is well drained in order to prevent seepage from undermining the concrete floor. Also, while small plants and grasses should be planted around the spring area to filter surface runoff and protect the spring from contamination, deep-rooted trees should be avoided as the root systems can clog the spring and damage the protection works. Finally, the outlet and overflow pipes placed into the intake structure should be sized so as to avoid the possibility of impounding the spring water during peak flow periods.

Spring water should be stored in an appropriate collection device. A small ferrocement tank of 500 or 1000 l capacity serves to store the water in most cases when the average discharge of the spring under consideration is below 0.1 l/s. If the flow of the spring exceeds 0.1 l/s then a storage tank may not be necessary and direct flow to the point of use could be provided. The size of the tank is determined based upon a minimum supply of 20 l per capita per day. Where a storage tank is provided, the top of the tank should be raised above ground level. The tank should be located as close to the catchment as possible, and the head difference between the intake and the tank should be sufficient to drain off the collected spring flow to the tank without causing a back-up or impounding of the water within the spring. The tank also should be protected by a fence.

An appropriate tapstand, including a washing platform with the provision for drainage, may also be constructed.

Extent of Use

The concept of spring development and protection was developed and initiated in Nepal during 1992 by the Department of Water Supply and Sewerage (DWSS). This technology has been used extensively in the Eastern Region of Nepal, moderately in the Central Region and rarely in the remaining three western regions, although the government has planned to implement spring protection projects in the all the regions of Nepal. This concept has been developed and is reflected in the policy and guidelines of DWSS.

Operation and Maintenance

Regular maintenance of the scheme is required and includes cleaning the storage tank regularly, protecting the storage tank and catchment area with fencing and grass plantings to minimise contamination, keeping the tap area clean and properly drained, and diverting surface water drainage away from the catchment area. Retaining walls should also be constructed on steep hillsides to mitigate landslides.

User participation in the project from the beginning, and contributions to the project by providing labour and locally available materials for its construction, ensures familiarity with the system. Users are trained in the operation and maintenance of the system, and one user is selected to act as the caretaker. This person is provided with some basic tools as part of the project cost. Since all the components of the scheme are located in close proximity to each other, the caretaker can maintain close observation of the users and the site, which reduces the chances of misuse of water or overuse of the system due to the limited capacity of the source. In many communities, users raise maintenance funds as part of the process of project implementation. However, some maintenance problems have been noticed due to the passivity of the users.

Level of Involvement

Spring protection schemes are generally implemented by the government, with active community involvement, with assistance from NGOs and international agencies such as UNICEF. Private construction has not been noticed as yet.

Costs

Direct capital costs include local and non-local materials, transportation, and labour. The average cost of a scheme is $500.

Effectiveness of the Technology

This technology is very effective and has brought about extensive improvements in the quality of water from the springs. The efficiency of utilisation has also improved due to the provision of storage capacity and conservation of water that previously was wasted during night.

Suitability

This technology is suitable in hilly regions where small springs with minimum discharges of 0.01 l/s are available. However, it should be noted that spring protection, in general, is not considered as an alternative to piped distribution system as it does not reduce walking distances or ensure provision of an adequate water supply. People benefiting from spring protection systems may request a piped distribution system at a later date.

Advantages

The technical advantages of the technology are:

- The technology is very simple and does not need any standard design procedure to be followed, making it replicable.

- It helps to augment available water resources which otherwise would not be used or considered "unhygienic" by the local people.

- The technology can be adapted to work in conjunction with other technologies such as gravity-flow, piped systems.

- Small springs can be developed to secure a supply of water during periods of extreme demand or when the main system fails for some time.

- There are fewer chances of disputes regarding the spring and its use as the users and developers of the water resource are the same.

- The entire construction can be completed within one week, once everything is available at the site.

- An high level of supervision and highly skilled operators are not necessary.

- The per capita costs are very low.

Disadvantages

Though there are no major disadvantages to this technology, some minor disadvantages are:

- The exact shape and size of the catchment structure cannot readily be predicted before construction, and inexperienced contractors may not be able to trap the flow properly with respect to the quality and quantity expected.

- Since the spring becomes "user friendly" after development of the protection scheme, demand may increase, and, if the yield is low, frustrations may arise within the user community.

- Since the benefit of this technology is solely in terms of improved water quality and yield, the community may not accept it as a "water supply" project, since it does not reduce the distances between source and point of use.

- In some cases, it may be difficult to site and construct the components of the system due to a lack of area or required head.

Cultural Acceptability

In general, the technology is very acceptable to communities, and people are appreciative of the user friendly system with safe water (instead of a dirty pond from which they previously used buckets to collect water). However, in some cases, people have opposed the excavation of the spring for fear that the source may dry up if touched; practically, this is not true, if handled properly. Also, in some areas, people believe that stored water is not fresh, and, hence, is not suitable for morning ablutions and puja (worship), although such beliefs are slowly disappearing.

Further Development of the Technology

This technology is still experimental in Nepal and needs to be further developed in terms of technology, construction, management and adaptability. The following points should be considered for further development:

- A detailed study should be carried out, and detailed guidelines prepared, to facilitate the use of this technology in a range of specific site conditions.

- Spring development techniques should be designed and implemented in such a way as to form the basis for installation of a piped distribution system in the future, especially with regard to intake structure construction.

Information Sources

Planning Section, Department of Water Supply and Sewerage, Kathmandu, Nepal.

3.15 Restoration of traditional stone spouts

Technical Description

This technology is a traditional water system in the Kathmandu Valley of Nepal. A typical stone spout is illustrated in Figure 20.

Figure 20. A Stone Spout.

Stone spouts are beautifully carved stone elements, in the shape of a crocodile head (considered as a holy water animal - the carrier of the Goddess Ganga) or serpent head, installed in the front or side walls of sunken and stepped platforms for the purpose of channelling water for human use. Each platform, or hiti, may contain one or more spouts. The spout(s) projects about 20 cm to 50 cm from the wall in which the spout is installed. The platform is usually constructed of stone slabs or bricks paved with mortar and fitted with a shallow overflow or drainage channel (generally provided with an iron screen). The surrounding wall is of brick masonry. Stone sculptures, idols and images of gods and goddesses are laid over and under the spout(s), on the surrounding wall and elsewhere in the compound. Despite their age, the underground supply and drainage lines of many old systems are still functioning, nobly characterizing the technical and engineering skills of the ancient people of Nepal.

The supply of water to the hitis depends both on ground and surface water. Most stone spouts receive water from either an individual spring or nearby aquifer. A single aquifer may supply water to one or many stone spouts. The stone spouts may be located within a particular, defined aquifer of known extent, or, more often, within aquifers whose locations and extent are unconfirmed. The aquifers are largely dependent on rainwater for recharge and maintenance of the groundwater table. Draw down of the water table in shallow aquifers may cause some stone spouts to yield less or become dry during the dry season. Some stone spouts only flow during the rainy season and remain virtually dry in other seasons.

Figure 21. Typical Porous Brick Chamber and Supply Line

To provide a continuous and uninterrupted supply of water from the stone spouts, a porous brick chamber is usually constructed surrounding the location of the underground channel from the aquifer. The porous base and the surround of the chamber provide stability to the channel and protect it. The supply line is made of brick, timber or clay or a combination of these materials. The timber used in the supply line is generally grooved in a lengthwise direction, and brick or timber planks are used as lids to cover them (Figure 21). To avoid contamination of the underground supply by the entry of surface water, sewage or other contaminants through suction, percolation or seepage into the supply lines, the supply lines, and especially the joints, are carefully covered with clay or red soil of limited permeability. The supply lines are generally located between 1 m and 5 m below the ground surface. The supply lines are sloped to maintained the flow of water.

TABLE 12. Maximum (Wet Season) and Minimum (Dry Season) Discharges from Stone Spouts in Nepal.

Stone Spout	Minimum Flow	Maximum Flow
	(m3/day)	(m3/day)
	8 March 1995	29 July 1995
Pulcowk hiti	19.872	371.522
Gain hiti	3.456	19.440
Cawa hiti	14.688	25.056
Tapah hiti	86.400	192.672
Nagbah hiti	-	143.424
Misa hiti	34.560	266.112
Konti hiti	248.832	412.128
Amrit hiti	70.070	105.105
Alkva hiti	267.494	361.152
Wasah hiti	42.163	29.808
Sainthu G. hiti	-	-
Cyasah hiti	129.600	600.480
Nay hiti	58.666	541.728
Bya hiti	3.456	5.011
Bhole hiti	-	2.592
Makah hiti	7.171	10.368
Subah hiti	-	69.984
Balkumari hiti	-	-
Guita hiti	-	-
Tyagah hiti	2.592	18.144
Sinci hiti	51.494	505.440
Nah hiti	71.712	106.272
Kanibah hiti	0.259	2.592
Thapah hiti	15.293	80.352
Saugah hiti	-	-
Sundhara hiti	89.683	142.560
Loh hiti	-	-
Thusa hiti	-	-
Mangah hiti	29.396	177.120
Tangah hiti	-	144.288
Loh hiti	-	-
Iku hiti	234.144	355.968
Hiku hiti	81.216	158.112
Jawalakhyo hiti	6.912	26.784
Gaa hiti	6.048	8.640
Mandap hiti	-	11.232
Bhole hiti - 2	-	20.736
Bhindyolachhi hiti	-	-
Total	1 575.157	4 596.436

In addition to protecting and ensuring a supply of groundwater for human use, the stone spouts provide for the filtration of the water. Water is conveyed through the supply line to vessels containing filter media placed just upstream of the spout(s). The technologies adopted to filter the water are not the same everywhere in Nepal, but can be categorized into two types of systems which have been popularly installed for filtration; namely, the sand filter and settling basin filter. The sand filter type consists of layered gravel and sand beds which act as the filtration media. Water from the supply line is passed through the layers, graded and placed from coarse to fine, which filter the water before it flows out from the spout (Figure 22).

Figure 22. Sand and Gravel Filter

The settling basin filter system consists of stone containers (whose shape, size and number may vary with the number of water spouts in a particular hiti) equipped with a hole or holes in the wall of the basin, set slightly below the brim. The supply line terminates at the stone container, which feeds directly to the spouts. The sand, soil or other foreign matter present in the water settle in this container and are retained, while freshwater flows through the spouts. This is how the water is filtered out using a stone container, as shown in Figure 23.

Extent of Use

Stone spouts have been extensively used in the Kathmandu Valley of Nepal since ancient times. A few are also scattered in other places such as Palpa in the western part of the country. However, time and the development of new technologies for water systems has brought further construction of stone spouts to a standstill. Thus, conservation of the existing spouts has been given priority by the government, which is expected to contribute to their maintenance and optimum utilization.

Figure 23. Settling Basin Filtration System.

Operation and Maintenance

To ensure the regular supply of water for irrigation, and to the pokharis and the stone spouts, a Watchman is appointed by the government and charged with the overall operation and maintenance of the supply canals. Thus, while the responsibility for the operation and maintenance of the system is borne by a municipality or the government, the day-to-day operation of the system rests with the community. Operation and maintenance activities, as a result, do not incur direct costs but are carried out voluntarily by the community.

Level of Involvement

It is of utmost importance to conserve and maintain the stone spouts, not only to augment freshwater resources but also to protect the spouts themselves, which are valuable national monuments. Government, the community and other non-governmental and private sector agencies often jointly mobilize their resources to protect and restore deteriorating traditional systems. Urban Development through Local Effort (UDLE), implemented under the Patan Conservation and Development Project (PCDP) and assisted by the German Agency Technical Co-operation (GTZ), has done commendable work in improving stone spouts and their allied water sources and pokharis in Patan, while the United Mission to Nepal (UMN) has undertaken a number of studies relating to groundwater resources. The conservation initiative of the community and municipality in recent years is also a praiseworthy step. The key element in ensuring a successful project is the effective coordination between all of the actors involved.

Effectiveness of the Technology

The effectiveness of any technology can be indicated by its performance. Water from the stone spouts is meant for drinking and other domestic purposes. Collection of water and bathing are usually allowed at all of the stone spouts; but cleaning utensils and washing clothes may not be allowed. However, the use of water is not limited to household purposes only; the spout waters are considered pure and holy and are used daily in religious functions, rites and rituals in temples and shrines. Some Baidyas (Ayurvedic homeopathic medical practitioners) also use water from certain spouts to prepare medicines, and there is a strong belief that the water has medicinal qualities used for treating diseases.

The stone spouts, traditionally built to supply water to a small population in a localised area, could take on much greater importance as the National Water Supply and Sewerage Corporation (NWSC) of Nepal is unable to supply the required amount of water to all of the population of Nepal due to the high rate of population growth and unplanned urbanization. Studies have shown that stone spouts benefit between 150 and 250 persons per spout in Kathmandu, and between 300 and 400 persons per spout in Patan, or between 3% and 4% and 4% and 6% of the total population, respectively, of Kathmandu and Patan. In the dry season, water from these spouts is carried in tankers and distributed in areas of water scarcity. Some stone spouts have shallow ponds, fed by overflow water from the spouts, located adjacent to them which are used widely for washing clothes, cleaning utensils, watering cattle and other purposes where high quality water is not essential, including the irrigation of downstream farmlands. Other stone spouts are connected to the municipal stormwater drainage system or directly discharged into rivers. Flows range from a minimum total daily discharge of about 1 575 m³/day during the dry season to a peak of about 4 596 m³/day during the rainy season. The average total daily flow is about 3 089 m³/day, a volume sufficient to theoretically supply some 31 000 people (assuming a per capita demand of 1001 per capita per day). While not all of this water is currently used for drinking (the volume of "useful water" is somewhat less than that of the average daily flow), the conservation and revitalization of the hitis could contribute to a reduction in the acute water shortage in Patan City.

Suitability

The stone spout technology is dependent upon the presence of an aquifer and the quality of the groundwater. Shallow aquifers are the primary source of water supplying the spouts, and should be free from possible contamination by surface water flows, seepage from sewer lines, etc. This technology is suitable in areas where the water table is not too low and where the groundwater quality is not disturbed by surrounding development.

Costs

No cost figures are available on the construction costs of the ancient spouts. However, the estimated cost of restoration of all of the spouts in the Valley is about $1 million.

Advantages

Revitalization of traditional water sources brings many benefits. Restoring the supply canals serves not only to fill the ponds which form a significant part of the traditional water supply network, but also serves to convey irrigation water to additional areas of fertile land, increasing crop yields and cropping intensity. Further, the abundant and permanent water in the ponds significantly contributes to the recharge of aquifers, stone spouts, wells and other small ponds. In addition, the revitalization work assists in the preservation of history, and restores the functions of the various elements of the ancient water supply systems to their original form. As the piped water supply system cannot reliably meet the full volume of water demand in Nepal, traditional water sources, such as the stone spouts and wells, remain potential, small-scale alternative sources of water supply. These sources can help to meet the water demand of the local community, and excess water can be redistributed to desired areas as needed.

Disadvantages

The restoration and revitalization of the stone spouts may involve the relocation of many buildings, constructed near the spouts, that are encroaching on public property. These buildings not only contribute to the disturbance of the natural aquifers and supply lines to the spouts as their impervious surfaces limit natural infiltration of rainwater, but also, since the spouts obtain water from shallow aquifers, to the contamination of the groundwater due to surface pollution. All of the spouts are reported to be contaminated in some way.

Cultural Acceptability

As the traditional stone spouts are believed to be a sacred heritage and as a system for their operation and maintenance exists among the local people of Nepal, cultural acceptability is not a problem with this technology. However, as water from some spouts is used for medicinal purposes and for sacred offerings to the gods and goddesses, conservation should be carried out with due regard to traditional societal beliefs.

Further Development of the Technology

If the stone spouts and the allied water sources are to be preserved and restored to function as historical water sources, reconstruction and restoration programmes must be carried out with due recognition to the hydrological cycle. The canals, which primarily serve to irrigate the land, also serve to recharge the ponds and aquifers, especially in the dry seasons. The revitalization of the canals, though not impossible, is a necessary and large-scale project which will make a significant and reliable contribution to the augmentation of the fresh drinking water supply available from stone spouts and wells.

Information Sources

G. B. Maharjan, (Local water user), Patan, Kathmandu, Nepal.

Dinesh Manandhar, D&M Associates, Post Office Box EPC4000, Kathmandu, Nepal, Tel. 977 1 410249, Fax: 977 1 410249, E-mail:[email protected].

Urban Development through Local Efforts, Project Office of UDLE/GTZ, New Baneshwor, Kathmandu, Nepal.

4.1 Desalination

Technical description

Desalination provides a means of upgrading poor quality, saline waters, and refers to a suite of technologies designed to produce freshwater from saline sources such as seawater or brackish groundwater. There are basically two types of desalination processes: reverse osmosis or RO technologies and electro-dialysis technologies. The techniques are similar in that both make use of membranes that allow passage of water molecules but exclude salts and other contaminants, which are discharged as a brine waste. In electro-dialysis, however, ions are transported through a membrane from one solution to another under the influence of a direct current electrical potential. The total concentration of soluble salts in water is expressed in terms of either salinity (35 parts per thousand or 35 000 mg/l of total salts being standard seawater) or electrical conductivity for diagnostic purposes. For example, saline water with conductivity of less than 2 250 microSiemens/cm are suitable for irrigation purposes. The major factors that determine which type of treatment is best suited to a particular application include the levels of salinity and temporary hardness; the presence of colloidal suspended matter, dissolved metal ions, oxidizing agents, and hydrogen sulphide; and temperature of the feed water, etc. (Crossley, 1983). The treatment of saline water using this technology began in the 1940s and continues with several hundred desalination plants operating throughout the Region. These range in capacity from a few cubic metres to more than 10 000 cubic metres per day (McRae, 1983). The largest plant built is in Baghdad, Iraq, which desalinates 24 000 cubic metres of water per day (Khan, 1986). In some areas of Asia, desalinization is vital to water supply.

The main components of a desalination plant consist of pretreatment and post treatment storage areas, power supply, membrane stacks, membranes, spacers, and pumps. Electro-dialysis plants also include electrodes. The brackish water is passed over a stack of several hundred ion-permeable membranes. In RO plants, the brackish water is passed across these membranes under pressure, while, in electro-dialysis plants, the brackish water is passed across these membranes at relatively low pressure as an electrical current is passed across the membrane stack. During the latter process, half the membranes allow positively charged ions to pass through and half allow negatively charged ions to pass through. Typical recovery rates using the electro-dialysis process range from 80% to 90% of the volume of feed water (Frederick, 1992). This process uses energy at a rate directly proportional to the quantity of salts to be removed and, for this reason, is usually used for the treatment of brackish water. This technology is very cost competitive for salinities up to 10 000 mg/l, but is not well suited for desalinating high salinity seawater. These technologies are relatively easy and simple to operate; are amenable to rapid delivery and installation; have fast start up and shut down capabilities; can be easily expanded to meet additional demand; and, require a relatively small amount of available space for installation. Small plants are often used for emergency water supply purposes.

Extent of Use

Desalination technologies were first conceived some 200 years ago and, by the 1930's, several small desalination systems were constructed in the Middle East. Since 1970, there has been significant commercial development using various desalination technologies, including distillation, reverse osmosis, and electrolysis, in the Middle East, where other options for freshwater augmentation are limited. Desalination technologies have been used to produce product waters with salinities below 500 mg/l (Khan, 1986). In Asia, a 9 072 m² plant was built in Gwadar, Pakistan, to desalinate sea water and, in Awania, India, a 1 867 m² plant was built to treat brackish water (Fenton, 1983). A United Nations study on the extent of use of desalination technologies and their potential use in developing countries, conducted in the early 1960s (Popkin, 1968), indicated considerable potential for adoption of these technologies in Asia, in India, Quatar, Saudi Arabia, Israel, and Kuwait.

Operation and Maintenance

The complexity of the operation and maintenance procedures for desalination technologies depends upon the type of technology used. Generally, however, an high level of expertise is required.

Level of Involvement

This technology has been implemented within the private sector at the level of individual industries.

Costs

The costs of reverse osmosis (RO) and multistage flash (MSF) desalination technologies have been tabulated by Tare et al. (1991) and are shown in Table 13. As shown, RO appears to be the least costly option for desalination, but, as their study concludes, the cost effectiveness will largely depend on the local specific conditions. For example, the cost of desalination using either technology will involve the costs of withdrawal of water from the sea and of pumping the seawater the plant. Nevertheless, in most cases, RO is usually the preferred means of desalinating brackish water (rather than sea water):

- RO with multi-stage flash (MSF) is a reliable alternative

- The capital cost of MSF is usually higher than RO due to high cost of importing the equipment

- At high capacities, the seawater intake volume is higher in MSF plants, and efficiency lower

- Power requirements are much higher in the case of RO plants because of their high pressure operation

- Though RO plants have lower initial investment and fixed costs, they have higher maintenance costs

- MSF plants require a greater land area, which can increase the cost due to high land prices.

TABLE 13. Comparison of Desalination Alternatives for Water Supply to Industry in Arid Areas.

Alternative	Capacity in MGD	Total Capital Cost in Million	Fixed Costs in $/m3	Power Cost in $/m3	Steam Cost in $/m3	Total Maintenance Costs, $/m3	Chemical, Labour, and Other Costs, $/m3	Total Costs in $/m3
RO	0.32	2	1.00	0.35	-	0.25	0.15	1.75
	1.00	5	0.75	0.35	-	0.25	0.10	1.45
	5.00	18	0.50	0.35	-	0.25	0.10	1.20
MSF	0.32	3.5	1.50	0.10	0.60	0.25	0.10	2.55
	1.00	7	1.00	0.10	0.60	0.20	0.10	2.00
	5.00	18	0.50	0.10	0.60	0.10	0.05	1.35

TABLE 14. Comparison of Alternative Industrial Water Supply Technologies in Arid Areas.

Process	Cost in $/1 000 m3
Desalination of seawater	$73 - $1 621
Importation	$566 - $670
Desalination of well water	$365 - $649
Wastewater reclamation	$292 - $473
Conversion	$162 - $567

TABLE 15. Component Costs of Production for MSF Desalination Plants at Various Capacities.

A) OPERATING COST:	COST $/m3
CAPACITY, MGD	0.32	1.00	5.00
CHEMICALS	0.01	0.01	0.01
LABOUR	0.06	0.04	0.03
POWER: 2.50 KWH/m3 @ $0.04/KWH	0.10	0.10	0.10
STEAM: 0.21 MT/m3 @ $2.85/MT	0.60	0.60	0.60
MAINTENANCE: 3% of Total Capital Cost Excluding Spares and Finance Charges	0.26	0.16	0.09
ADMINISTRATION and OVERHEAD: 100% of Labour	1.09	0.95	0.86
TOTAL OPERATING COST
B) FIXED COST PER ANNUM:
TOTAL CAPITAL COST: $ Million	3.5	7.0	18.0
COST OF CAPITAL: 20 years @ 15% interest	1.50	1.00	0.57
C) TOTAL COST OF PRODUCTION:	2.59	1.95	1.43
APPROXIMATE TOTAL COST	3.00	2.00	1.50

TABLE 16. Component Cost of Production for RO Desalination Plants at Various Capacities.

A) OPERATING COST	COST $/m3
CAPACITY, MOD	0.32	1.00	5.00
CHEMICALS	0.03	0.03	0.03
POWER: 8.61 KWH/m3 @ $0.04/KWH	0.36	0.36	0.36
LABOUR	0.06	0.04	0.03
MAINTENANCE: 3% of Total Capital Cost Excluding Membranes, Spares and Finance Charges	0.12	0.09	0.06
MEMBRANE REPLACEMENT: 20% of Membrane Cost	0.06	0.04	0.03
ADMINISTRATION and OVERHEAD: 100% of Labour	0.79	0.72	0.67
TOTAL OPERATING COST
B) FIXED COST PER ANNUM:
TOTAL CAPITAL COST: $ Million	2	5	18
COST OF CAPITAL: 20 years @ 15% interest	0.88	0.70	0.52
C) TOTAL COST OF	1.67	1.42	1.19
PRODUCTION:	2.00	1.50	1.00
APPROXIMATE TOTAL COST

Effectiveness of the Technology

Using desalination technologies, water supply can be increased incrementally with demand, by installing modular equipment in stepwise fashion, whereas other technologies generally require that the total investment be made at the beginning of the water resources development project. Desalination technologies also can be quickly installed, providing a rapid augmentation of freshwater supply without conflicts over traditional water rights. On this basis, the US Department of the Interior concluded that desalination is an entirely viable means of increasing water supply, at least from the point of view of technological feasibility (Clawson and Landsberg, 1972).

Suitability

This technology is suitable for use in areas where freshwater is scarce, but saline water is available and energy is cheap.

Advantages

Compared to water recycling technologies, desalination presents fewer health risks. The modular nature of this technology, using "packaged plants", makes desalination useful in emergencies and for small-scale applications.

Disadvantages

Desalination is expensive. It is energy intensive and incurs high energy costs. Its technical complexity may limit the ability for the technology to be introduce without a major realignment of the institutions.

Cultural Acceptability

Desalination is a new technology, and requires further testing before its cultural acceptability can be determined.

Further Development of the Technology

The application of desalination principles in a less expensive and less complex form is being undertaken. For example, the solar still is a low energy technology which has the future prospect of providing inexpensive desalinated water. There is also the prospect of using desalination technologies in combination with other technologies, such as multistage flash evaporation, as a means of reducing the high energy costs associated with the technology. The selection of this technology to augment public water supply purposes depends on many factors, including product water quality and quantity required; source water characteristics, temperature and reliability of supply; energy availability; and, the relative location of the consumers to the source.

Information Sources

Crossely, LA. 1983. Desalination by Reverse Osmosis, In: A. Porteous (ed.), Desalination Technology: Development and Practice, Applied Science Publishers, London.

Fenton, G.G. 1983. Solar Distillation, In: A. Porteous (ed.), Desalination Technology: Development and Practice, Applied Science Publishers, London.

Khan, A.H. 1986. Desalination Processes and Multistage Flash Distillation Practice. Elsevier, Amsterdam.

McRae, W.A. 1983. Electrodialysis, In: A. Porteous (ed.). Desalination Technology: Development and Practice, Applied Science Publishers, London.

Popkin, R.1968. Desalination: Water for the World's Future, Frederick A. Praeger Publishers, New York.

Tare, M.M., et al. 1991. Economics of Desalination in Water Resource Management - A Comparison of Alternative Water Resources for Arid/Semi-arid Zones in Developing Countries, In: M. Balaban (ed.). Proceedings (Wl.1) of the 12th International Symposium, Institute of Chemical Engineering (UK), London.

4.2 Pond sand filtration

Technical description

In Bangladesh, Pond Sand Filters (PSFs) are built around artificially constructed ponds, locally known as "sweet water ponds" which are replenished by rainwater during the monsoon season. In these systems, rainwater collected in these ponds is pumped by hand into a storage tank through a filter chamber. The filter chamber is constructed in two parts, the first of which is a pre-filter packed with coconut fibres. This pre-filter reduces the turbidity of the raw water as the raw water flows into the filter chamber. The outflow from the pre-filter flows into the main body of the filter chamber through two overflow pipes. The main filter chamber consists of a layered, sand filter bed, through which the water trickles and in which impurities, including bacteria, are removed in a manner similar to slow sand filtration. The quality of the raw water is further protected through the reservation of the ponds feeding into the filtration system solely for potable water use. Details of this technology are provided in Part C.

Extent of Use

In Bangladesh, numerous Pond Sand Filters have been constructed. About 90 PSFs, each serving about 50 to 60 households on the average, have been constructed in Dacope thana since the start of the PSF programme in 1984. In Kaliganj thana, there are about 24 PSFs, all constructed during 1993-94. The average life of a PSF is a minimum of 10 years. The use of PSFs has the potential to revolutionize the drinking water systems in the saline areas in the southern belt of the country, covering the Greater Khulna, Patuakhali, Barisal and Noakhali districts.

Operation and Maintenance

Operation and maintenance requirements relate primarily to the handpump used to transfer the water from the ponds to the filtration units. The expenses associated with this are borne by the community. Initially, the Bangladesh Department of Public Health Engineering (DPHE) supplies necessary tools to the caretaker family to maintain the pump as required, and the users make minor repairs themselves. If major repairs are needed, and the related maintenance expenses are large, the community can apply to the DPHE for assistance. Operation of the PFS pump is generally by the users who pump and filter enough water for their own use.

Routine cleaning of the PSF is required. The rate of filtration gradually decreases over time, with the length of run resulting in increasing head loss. In order to maintain a constant rate of filtration, the height of water above the sand bed can be increased; however, a time will come when the filter bed must be cleaned to retore a reasonable rate of filtration. When the turbidity of the pond water is less than 8 NTU, the usual time between cleanings is about five months. When the turbidity increases to 30 NTU, it may be necessary to clean the filter every one and half months. The length of run also depends on the number of users drawing water from the system. Cleaning of the PSF is very simple and can be accomplished by two persons in under 45 minutes.

Level of Involvement

Adoption of this technology is at the community level. In Bangladesh, prospective users of this technology apply to the Department of Public Health Engineering (DPHE) for technical assistance, acknowledging their willingness to build and operate a PSF. This undertaking a willingness not only to transport the required materials to the site from pick-up points, but also to provide labour. Brick-makers, as well as a mason, plumber and carpenter, are provided by the community as needed during the construction of the PSF system. The community also nominates two men and two women (caretaker families) to be trained in the maintenance of the PSF when it is handed over to them by the DPHE. The community then takes full responsibility for the cleaning, maintenance and repair of the PSF.

Costs

The PSFs in Bangladesh cost about $ 1 500 each to construct, depending on size. This cost is currently met to varying extents by the DPHE, depending on the degree of need within the community and the ability of the community to fulfill the DPHE criteria governing provision of these systems.

Suitability

This technology is suitable for use in areas where there is adequate (seasonal) rainfall. In Bangladesh, the use of this technology is limited to those areas lacking access to adequate groundwater sources which can be accessed using tubewells are found to be successful in the location. In the areas where PSF systems have been developed, tubewells are not successful as suitable fresh water aquifers are not available at reasonable depths. Groundwater is saline down to depths of 200 m to 350 m, and naturally-occurring surface water sources are saline and also polluted.

Effectiveness of the Technology

The present version of the Pond Sand Filter (PSF) system is a great improvement over the older design, which did not incorporate the pre-filter nor did it protect the source water from contamination. The PSF is capable of producing a potable product water from a pond water source, removing both harmful organisms and impurities, and turbidity. The iron content of the product water is also reduced. This has contributed to a considerable reduction in the incidences of water-borne diarrhoeal diseases. The technology also provide a convenient platform for drawing water, washing utensils, etc. A 1989 survey of PSF users in Dacope by the DPHE and UNICEF indicated that:

- users were satisfied with the quality of the product water,

- 84% of users were female,

- users travelled an average of 0.5 miles, with a maximum distance travelled of 1.5 miles, to obtain potable water,

- 100% of users used the water for drinking, 80% used it for cooking, and 13% used it for washing; other water sources used were area ponds and rivers, which were used mainly for washing and cooking purposes,

- 36% of users used the water throughout the year, and 59% use it only in the dry season,

- during the dry season, users spent up to 20 minutes waiting to obtain water during periods of peak demand; longer delays discouraged water users, who tended to use nearby unprotected sources of water instead of the PSF treated water.

Advantages

This technology can be built to serve a large community. Use of this technology induces community cooperation in the provision of safe drinking water supplies.

Disadvantages

The major limitation of this technology is raw water storage. The pond must be large enough to ensure that it will not dry out in the dry season. It is also important to ensure that the salinity and iron content of the pond water not exceed 600 ppm and 5 ppm, respectively, at any time of the year.

Cultural Acceptability

This technology is very well accepted. The active involvement of the community demonstrates an high degree of community acceptability at the local community level.

Further Development of the Technology

This technology may be considered fully developed.

Information Sources

Contacts

Mohammed Aslam, Saleh Ahmed Chowdhury, Alamgeer Faridul Hoque, and S.R. Sanwar, Intermediate Technology Group, House 32, Road 13A, Dhanmondi, Dhaka, Bangladesh, tel. 880 2 811 934, fax: 880 2 813 134, E-mail: [email protected].

Bibliography

DPHE and UNICEF 1989. A Report on the Development of Pond-Sand Filter. Department of Public Health Engineering, Dacca.

4.3 Biological pretreatment of raw water

Technical description

This technology is being used in China to pre treat slightly polluted water sources which have to be used as raw water sources for water treatment works. Generally, such sources are polluted by wastewater, and the primary concerns relate to the presence of carbonaceous and nitrogenous compounds in the raw water which may not satisfy water source standards. Most water treatment works commonly use a coagulation-sedimentation-filtration-disinfection process. However, when polluted water is used as a source water to produce water for public consumption, reactions between carbonaceous compounds in the raw water and Cl₂ used in the disinfection stage, and between Cl₂ and nitrogeneous compounds in the raw water, results in formation of compounds such as trihalomethanes which are harmful to human health. These compounds also consume greater volumes of Cl₂, beyond those necessary for disinfection, resulting in a waste of Cl₂. In such cases, bio pretreatment is one options for improving the safety and quality of the water produced by the waterworks. Various kinds of commercial plastic products may be used as growth substrates to promote biological pretreatment of the raw water. Alternatively, sometimes local materials such as the shells of shellfish can be used for this purpose in coastal cities. The treatment process is shown diagrammatically in Figure 24.

Extent of Use

This technology has been used by small municipalities and industries.

Operation and Maintenance

Biological pretreatment of raw water feeds to waterworks requires good operational and maintenance supervision by qualified staff. Constant monitoring of the water quality parameters is also necessary. Such monitoring requires a fully equipped laboratory and trained staff to operate the laboratory equipment.

Level of Involvement

This technology is typically implemented at the municipal level or at the level of individual large industries.

Costs

Table 17 summarises the costs associated with the use of this technology.

TABLE 17. Cost of the Biotreatment Process in China

Electricity	0.32KWH/m3	$15/1 000m3
Labour	18 persons
Coagulant	0.025Kg/m3	$7/1 000m3
Liquid Cl2	0.004Kg/m3	$1/1 000m3
Chemicals		$0.25/1 000m3
Maintenance		$3/1 000m3
Total		$26.25/1 000m3

Figure 24. A Process Diagram for Biological Pretreatment

Effectiveness of the Technology

This is an effective technology for ensuring the quality of raw water for municipal and industrial purposes. Tables 18 and 19 present an example of the effectiveness of this technology from a glass factory in Zhejiang Province, China. Table 18 shows the water quality parameters of the water source used by the glass factory, and the industrial water standards. Table 19 shows the water quality of the product water at various points in the treatment process (refer to Figure 24).

TABLE 18. Source Water Quality and Industrial Water Standards for Industrial Use.

Parameter	Unit	Source Water In the Canal	Quality Standard Required for Industrial Use
pH		7.84	6.0-8.0
COD	mg/l	<60.7	20
BOD	mg/l	<40.3	6
SS	mg/l	<139	20
Turbidity	NTU	-	5
Odour, taste	-	-	No offensive odour or abnormal taste
SO4	mg/l	57.9	-
Fe	mg/l	2.55	0.3
Cl	mg/l	74.85	-
Oil	mg/l	0.39	0.20
SiO	mg/l	28.4	30
Conductivity	mS/cm	420	-
Free Cl2	mg/l	-	0.3

Advantages

This technology is effective in reducing the concentrations of pollutants in natural waters, thereby improving water quality for a variety of water uses after application of conventional water treatment techniques.

Disadvantages

The primary disadvantage of this technology is that it requires trained staff to implement. The biological pretreatment technology needs to be carefully controlled and closely monitored to ensure consistent quality product water is produced.

Cultural Acceptability

This technology is acceptable, with no known cultural problems.

TABLE 19. Effluent Water Quality Using Biological Pretreatment Processes in China.

Influent: pH 7.5, COD 30-90 mg/l, SS 80-90 mg/l, Turbidity 35-90 NTU, NH3-N 0.95 mg/l
Effluent
from anaerobic tank	NH3-N	0.8mg/l
from anoxic tank	NH3-N	0.7mg/l
from aerobic tank	COD	20 - 40 mg/l
	SS	45 - 55 mg/l
	Turbidity	44 020 NTU
	NH3-N	0 - 25 mg/l
from sedimentation tank	Turbidity	2-10 NTU
	Turbidity	0.5 - 3 NTU
filter	pH	6.5 - 7.0
	COD	10 - 25 mg/l
	SS	5 - 7 mg/l

Further Development of the Technology

This technology is considered to be fully developed. Pilot projects are needed to popularize the use of this technology.

Information Sources

Professor Chi Bute, Tingji University, 1239 Shiping Road, Shanghai 200009, China, Fax: 86 2165028965.

5.1 Water conservation and recycling - Gujarat State fertilizer corporation, India

Introduction

Gujarat State Fertilizer Corporation (GSFC) is one of the largest integrated fertilizer and petrochemical complexes in India, producing a variety of fertilizers, intermediates and petrochemical products. GSFC has adopted an integrated approach to conserving water. This strategy has brought multiple benefits to the operations of company. By recycling their effluent streams, GSFC substitutes recycled water for raw water in their water stream, resulting not only in water conservation and cost savings, but also in the recovery of chemicals previously discharged in the process and an higher level of water pollution control compliance. Water consumption has been maintained at a low level, despite the expansion of the plant and increased production levels.

The raw water supply to GSFC is met from two sources:

· From a joint water supply scheme with Gujarat Refinery, using French-type, radial collection wells situated in the bed of the Mahi River, which provides up to 36 370 m3/d.

· From GSFC-owned French-type, radial collection wells, situated in the bed of the Mahi River at Parthampura, which supply up to 45 460 m3/d.

The actual throughput of these wells is dependent on groundwater levels. During drought periods and in the summer months, the groundwater levels drop, limiting the throughput of the wells. Nevertheless, the primary source of water supply to the GSFC operations is the jointly-operated Gujarat Refinery well and balance is met from the GSFC-Parthampur installation. The total daily water requirement of the GSFC operation prior to the installation of the water conservation and recycling practices as about 45 000 m3/d. Specifically, the water requirement of the GSFC plant, after Phase I, II and II expansions in 1977, was:

(i)	Cooling Tower Make-up Water	24 400 m3/d
(ii)	Demineralized Water Production	9 000 m3/d
(iii)	Process Water	3 000 m3/d
(iv)	Fire Protection Water	1 000 m3/d
(V)	Drinking Water	3 000 m3/d
(vi)	Township Water Supply	5 000 m3/d
	Total	45 400 m3/d

With the implementation of the integrated approach to water conservation and recycling of effluents, the present water requirement of the GSFC complex is 40 000 m3/d. Use of these technologies has helped to maintain water demands at GSFC at a low level, despite an increased level or production and an increased number of operating divisions (Table 20).

TABLE 20. Water Consumption in the Industry (GSFC).

Year	Average Water Consumption (m3/d)	Fertiliser Production (Metric Tonnes)	Capacity Utilisation (%)
1983	31685	616000	87
1984	35370	742 000	105
1985	33822	759 000	108
1986	36822	808 000	115
1987	34822	772 000	110
1988	36004	845 000	120
1989-90	36277	919000	130

Technical Description

GSFC opted for an integrated approach to water conservation and recycling based upon the philosophy that conserving water conserves all resources associated with the water. Conservation of steam, condensate, demineralised water, and process water leads to the conservation of water with maximum returns. For example, within a network of plants, it was possible to recycle waste stream from one plant to another plant. As a practical result of this recycling philosophy, the phosphatic group of plants achieved the total recycling of its effluent, conserving water, recovering previously lost product and controlling pollution. Similar strategies were adopted in the ammonia/urea group of plants. Some of the actions taken to conserve water are elaborated in the following sections.

· Recycling acidic effluents in chalk ponds

Chalk is a by-product produced by the ammonium sulphate plant. Chalk slurry is pumped to chalk ponds where it is mixed with highly acidic, phosphoric acid contaminated return flows. The acidic effluent is neutralized by chalk slurry and the chalk floc settles in the pond. Two chalk ponds have been sealed with polyethylene linings on their bottoms to minimise water percolation. After a period of operation, the ponds fill with chalk and must be emptied; hence, the requirement for two ponds to ensure continuous operation of the plant. During the time when the first pond is off-line and being emptied, the second, empty chalk pond is filled with water to bring it on line. Annually, 170 000 m³ to 180 000 m³ of chalk is reclaimed using this process and an equivalent amount of water is consumed in filling the chalk ponds before they are commissioned. Cooling water can be used to meet this initial water requirement. Alternatively, effluents from ammonia/urea, melamine, and caprolactum plants can be used after treatment to strip the ammoniacal nitrogen. These effluents are collected in a central collection pond, pumped to the polyethylene-lined ammoniacal effluent lagoon, and treated in an Air Stripping Tower to remove ammoniacal nitrogen, before being discharged to the chalk pond or disposed. In normal plant operations, this reclaimed water is also used as make up water for the chalk ponds.

· Recycling barometric condenser water as cooling water

In the evaporation section of the ammonium sulphate plant, there is a surface condenser followed by two barometric condensers, for vacuum generation. The gases, after coalescing in the surface condenser, are condensed in the barometric condenser through direct contact with the cooling water. The barometric condensers use cooling water at a rate of 135 m³/hr. Rather than discharge this cooling water, as was previously the case, the barometric condenser water is now segregated from the main effluent disposal grid and is pumped back to cooling tower of ammonium sulphate plant, recycling 135 m³/hr of cooling water.

· Recycling contaminated condensate for chalk repulping

Process water condensate, generated in the evaporation process employed in the ammonium sulphate plant, is contaminated and cannot be directly reused. Thus, in excess of 30 m³/hr of process condensate had been historically discharged as effluent. However, water was required elsewhere in the ammonium sulphate plant to repulp chalk after it had been used in the filtration of ammonium sulphate plant liquor. The filter cloth must also be washed with water at the same time. In order to conserve water, a system was designed to substitute process effluent, mainly process water condensate, for the non-recycled cooling water that had been previously used for this purpose. All contaminated process water condensates from different sources with GSFC are collected in a central collection pit, and pumped to the chalk filter to wash the filter cloth and to repulp the chalk. The resultant chalk slurry is pumped to the chalk pond for settling and neutralization of acidic wastewaters as described above.

It should be noted that, as this repulping and washing stage is one of the most critical in the entire operation, automated safeguards were provided to ensure that the process remained unaffected in case of any problems being experienced with the effluent recycling system. However, the recycling system is working well, with two ammonium sulphate plants being successfully operated with total recycling of the effluents to the chalk pond. This has provided significant savings in cooling water requirements, enhanced recovery of ammonium sulphate, and increased the level of water pollution control achieved.

· Recovery of pure condensate as brine-free water (BFW)

In the ammonium sulphate plant, a 40% ammonium salt solution is evaporated to produce ammonium sulphate crystals. Steam is used as the heating medium to evaporate the saline solution. Condensate from both parts of the process, previously lost as waste, is now captured in the main condensate grid as part of the process design. The purity of the condensate is analysed, with the pure condensate being directed into a separate circulation system and pumped to the steam generation plant to be used as brine-free water. Quality safeguards and process safeguards are provided so that process is not affected by any malfunction of the operational control systems.

· Recycling phosphoric acid plant effluent from the chalk ponds

In the phosphoric acid plant, water from the chalk ponds, described above, is utilized in the fume scrubbers, condensers, and flash cooling systems, and in other, miscellaneous services. The acidic return flows from the plant are pumped back to the chalk ponds for neutralization, settling and natural cooling. The cooled chalk pond water is returned to the phosphoric acid plant and remains in circulation until the build up of dissolved solids (TDS) in recirculating water begins to impair its effectiveness as a coolant, at which point, the chalk pond water is bled off to control the TDS build up. The water lost through this bleed off is subsequently made up by the addition of new cooling water. The high TDS water is discharged as effluent.

Also in the phosphoric acid plant, process water was used for gypsum repulping and washing of the cloth pan/belt filter. The cloth filter captures the gypsum cake and conveys it to a discharge point, after which the cloth is washed by a number of spray nozzles located on both sides of the belt. To conserve water, the same wash water is used for repulping the gypsum cake and conveying the gypsum slurry to the drum filters where it is further purified. As a further conservation measure, chalk pond water is substituted for process water throughout the process. Chalk pond water is mixed with condensate for use in filter cloth washing and gypsum repulping.

As a further benefit of this recycling scheme, about 2 500 metric tonnes of ammonium sulphate is recovered annually from the chalk pond. The chalk pond water contains 1.5% to 2% ammonium sulphate which is recovered in the phosphoric acid process in form of diammonium phosphate (DAP). The recovery of ammonium in the form of DAP has had a tremendous impact on profitability, and has clearly demonstrated the benefit of the integrated effluent recycling, recovery and pollution control programme.

· Recycling chalk pond water in the grinding mill dust scrubber

In the phosphoric acid plant grinding mill, there is dust scrubber to recover rock phosphate dust downstream of the product cyclones. This is a wet scrubber, which used process water at a rate of 95 m³/hr. The resultant slurry was recycled to the phosphoric acid digester. As part of the water conservation programme, chalk pond water was substituted in place of the process water.

· Recycling process water condensate in the gypsum purification section

In the gypsum purification section of the phosphoric acid plant, gypsum cake was collected on a drum filter and washed off the filter using hot water jets. Process water, heated with live steam, was used for this purpose at a rate of 5 m³/hr. As part of the integrated water conservation programme, hot condensate was used in this process.

· Demineralised water conversion in barometric condenser cooling tower

In the urea plants, cooling water is used in the crystallization section of the barometric condensers for vacuum generation. The barometric condensers are cooled in the barometric condenser cooling tower. The cooling water used in this process is contaminated with ammonia and urea due to its closed loop circulation and to process upsets which result in carry overs of ammonia and urea. Hence, it is necessary to make up the cooling water supply by bleeding the contaminated cooling water from the cooling tower to maintain water quality. This created a continuous flow of liquid ammoniacal effluent from the bleed of the cooling tower, and the subsequent consumption of cooling water supplies. As part of the water conservation programme, the cooling towers were converted to a demineralized water circulation and cooling water system in which the cooling towers were isolated. After demineralized water circulation, excess water from this cooling tower was substituted for demineralized water used in the plant.

· Recycling of effluent in the diammonium phosphate plant

In the diammonium phosphate plant, pre-neutralizer temperature control is accomplished with the addition of process water. Temperature control is quite critical for plant operation. As part of the water conservation programme, water from washings and leakages, etc., was collected in a pit and substituted for process water in the temperature control function. As in other critical systems, an automated temperature control system was retained in the process so that the process is not affected by problems with the effluent circulation system.

· Renovating water at the sewage treatment plant

GSFC Township houses about 1 700 families in a setting that has vast areas of open land with lawns, plants and recreational facilities. Sewage water from the Township was pumped into the main effluent grid and discharged with other plant effluents at a rate of 230 m³/hr. As part of the water conservation programme, an activated sludge sewage treatment plant has been installed and commissioned recently, which reclaims about 135 m³/hr of treated effluent as cooling water and irrigation water for the Corporation's experimental farm.

· Recycling of clean water in the cooling towers

In the industrial complex, there are number of applications in which cooling water is used for open cooling. The spent cooling water was typically released as waste through the sewers. To minimize this loss of water, many of the open cooling water applications were converted to jacketed cooling water operations. Cooling jackets were installed on transfer lines, secondary transformers, high tension shift converters, and other equipment, with the return flows of spent cooling water sources being diverted to cooling towers. Similarly, water from air conditioner package units was diverted to suitably modified cooling towers. All of these measures resulted in a substantial savings of cooling water.

Operation and Maintenance

In every water conservation project which recycles cooling water or substitutes recycled water for process water, continuous monitoring is needed to ensure that the recycling practices do not result in any disruptions to the process, or to contamination or problems of corrosion in the equipment. In the case of GSFC, special attention is given to:

· monitoring of the chalk pond effluent, as well as monitoring of the ponds for any seepage into the ground

· monitoring of cooling water quality at critical points in the cooling water stream

· monitoring pump performance, especially of those pumps handling effluent

· maintaining and testing the automatic safeguards installed to ensure continued plant operations in the case of problems with the effluent recycling system, especially at critical points in the process

· analysing the purity of the condensates during the recovery of ammonium sulphate crystals, and providing the necessary quality safeguards and process safeguards so that process is not affected by any malfunction in the control systems

· controlling the continuous circulation of recycled water to maintain optimal cooling effectiveness in the plant, and replacing the recycled water with fresh water as necessary to minimize TDS build up

· maintaining and testing the automatic temperature control systems to ensure continued plant operations in the case of problems with effluent circulation system, especially at critical points in the process.

Level of Involvement

The project was implemented at the individual industry level, with major involvement of the senior middle level management of the company. The cooperation of the staff and the support of the top management were the additional factors in its success.

Effectiveness of the Technology

Various benefits were achieved as a result of the water conservation projects implemented at GSFC. A summary of the quantifiable benefits associated with this integrated programme of water conservation and recycling is presented in Table 21 for each component activity of this project. In addition, there were numerous unquantifiable benefits derived from the project, which are not listed.

Advantages

The advantages of undertaking water conservation projects were several. First, GSFC conserved water resources while increasing their productivity and profitability. Second, water conservation led to a significant reduction in the cost of water purchased. Third, water conservation reduced the volume of effluent generated in the production process and reduced the cost of effluent handling and treatment. Fourth, the energy required for plant operations was also greatly reduced. The programme also enhanced the ability of the Corporation to achieve its water quality goals.

TABLE 21. Water Conservation Benefits Achieved through Integrated Water Management in Industry.

Project	Quantified Benefit
Recycling of effluent from the chalk ponds	Annual savings of 170 000 m3 to 180 000 m3 of cooling water were attained.
Recycling barometric condenser water in cooling water	Recycling of 135 m3/hr of cooling water was achieved.
Recycling of contaminated condensate for chalk re-pulping	Savings of 30 m3/hr of process water condensate as well as ammonium sulphate recovery.
Recycling chalk pond water in the phosphoric acid plant	Recovery of about 2 500 metric tonnes of ammonium sulphate in the form of diammonium phosphate. Savings of 95 m3/hr of process water.
Recycling process condensate for gypsum purification	Savings of 5 m3/hr of process water by substituting hot condensate.
Renovating water at the sewage treatment plant	About 135 m3/hr of treated sewage is recycled as cooling water.

Disadvantages

In all of the water recycling projects, and especially in those related to cooling water within the GSFC plants, there was an increase cost associated with monitoring water quality to optimize both the cooling benefits and level of water conservation. Additional control systems were also required to ensure the proper functioning of the plants which use recycled flows.

Further Development of the Technologies

Water conservation is an attractive option for large and complex industries like GSFC to reduce the water costs, increase production and decrease the consumption of energy. The. experience in a public sector organization like GSFC has shown that water conservation is possible and profitable on a large scale. The experience at GSFC can be easily transferred to other fertilizer or other complex industrial units for getting similar benefits.

Information Sources

Contacts

S.M. Singh and C. M. Patel, Gujarat State Fertilizer Corporation, Baroda, India.

Bibliography

The Fertilizer Association of India s.d. Water Conservation in Fertilizer Industry; A Workshop Report, The Fertilizer Association of India.

5.2 Traditional methods of soil and water conservation - coconut pick-ups, India

Introduction

"Coconut pick-ups" is the term popularly used to describe diversion weirs constructed exclusively to benefit coconut gardens. The "pick-ups" are small structures built across seasonal or perennial streams to slow the flow of water at appropriate locations. This results in surface water storage, groundwater recharge, reduction of soil loss due to erosion, and provision of water for other activities. The technical concept is simple; i.e., to slow the flow of water at strategic places in order to collect water using bunds constructed of locally available materials, like stones, boulders or clay (mud). Mud bunds are turfed with a specific variety of locally available grass, Maane hullu. The bunds are usually built within an incised stream bed almost to the height of ground level, depending upon the width and steepness of the stream. During periods of peak stream flows, the berm creates an hydraulic obstruction which backs up the water, flooding the coconut plantations located on either side of the stream. The water impounded in this manner generally recedes within 3 to 4 days. In addition to supplying the plantations with water, the flood leaves a few millimetres of silt, and associated major and micro nutrients and organic matter derived from manure, leaves and the mineral carried downstream, particularly during the early monsoonal flows. Excess water subsequently flows into a storage tank. Sometimes there will be several coconut pick-ups and tanks within a catchment, and excess flows may be conveyed from one tank to another.

This case study illustrates the utility of this technology by reference to a pick-up located in the Tumkur District of Karnataka. Tumkur District receives an average annual rainfall of 688.4 mm. The net irrigated farming area accounts for 13.8% of the net farming area, and extends over 77 673 ha., 361.7 ha of which are irrigated with water supplied from tanks. Tumkur District stands third in terms of the number of pick-ups in active use, after the Mandya and Chikmagalur Districts.

The Coconut Development Board has provided $150 000 to state governments for pick-up construction under the million wells scheme. The amount spent on each pick-up will vary depending on the command area served by the pick-ups. Normally petitions are submitted by the villagers through their local government bodies (such as gram or mandal panchayats) to the zilla parishad or public works department. A survey of the site proposed by the villagers is conducted by the public works engineer, and an estimate of the construction cost is sent for approval to the district level engineer. After the technical evaluation, a financial sanction is obtained, and a contract is awarded to the registered contractors. Construction work is undertaken usually during the summer season.

Technical Description

The construction site is selected in an area with exposed bedrock to ensure a strong foundation. The stream is also narrow at such sites, and the sites typically form convenient sites for road crossings. Upstream of these constrictions, there is generally an area available for spreading the water more widely (the floodplain of the stream), and the back water created by the pick-ups can extend up to nearly one-half of a kilometre in length.

During the construction phase, a cofferdam created by about 200 polyethylene sandbags are used to make a temporary bund. Within this bund, boulders are placed upon the bedrock in a slanting manner to form a permanent bund. Each stone weighs between 100 kg and 1 000 kg, and are generally transported to the site in a power tiller trailer over a distance of between 0.5 km and 5 km. Wooden planks are used to load and position heavy stones. Behind this rock wall, a supporting vertical wall with a width of 10 cm is built, and both walls are raised simultaneously. Between the walls, an impervious core is created by a layer of "crude jelly" (bitumen) encased within a layer of clay. The clay is wetted to produce a slurry which is compacted by repeated passes of the power tiller to ensure a good seal, and further clay is added until the entire structure is encased in earth. Construction usually takes place over a period of several years.

During the first year, the total height of the bund is only about 5 cm above the stream bed, although the side embankments or wing walls are constructed on either side to a height of 10 cm to prevent the failure of the banks during periods of high flow, when the structure is overtopped. On either side of the bund, stone pillars are erected to enable people to locate the bund during peak flow periods, and to assist them in crossing the stream when the pick-up overflows. During the second year, after observing the water flow of the previous year to determine the effects of any seepage, overflows (possible flanking of the wing walls) and impoundment (to determine the ability of the structure to withstand the water load), further construction occurs and the height is increased by another 4 cm. The length of the pick-up increases as the height increases. During the second year also, work is completed prior to the monsoon. During the third year, after observing the water flow, the height is further increased by another 4.5 cm until it almost reaches the ground level. On completion, the surface of the pick-up is covered with stone slabs to prevent erosion of the clay surface. At this juncture, the entire structure is encased within a mud embankment, built to a height of 0.75 m (2-1/2 feet) above the stream bed, and turfed with Maane hullu grass to prevent erosion and stabilize the stream banks.

The Tumkur pick-up, constructed in the above manner, is almost impervious and has withstood even the heavy stream flows in the last five years (since 1991).

Extent of Use

The Tumkur pick-up is a typical coconut pick-up, and is one of five such structures situated on this water course. The Tumkur pick-up was selected for this study as information was available for the entire period of the construction project and for the 7 year operational period. It is the third pick-up in the catchment. The watershed of the Huvinahalla Stream which feeds the pick-up originates in the Handanahalli Hills. Stream flow is seasonal, with the stream flow dependent upon the annual rainfall. Nearly 90% of the stream reach passes through coconut plantations or gardens.

The Tumkur pick-up was designed and built by an individual farmer, and constructed using locally available materials. The design was approved by, and construction inspected by, the public works department prior to the implementation of the project. The formal inspection process and granting of operating permission by the public works department is intended to avoid litigation by downstream farmers. The project was completed over a span of three summers, with the height of the pick-up being raised each year until the crest of the weir was almost at ground level. The crest of the weir is stabilized and is used as a cross-over road to reach the other stream bank during high flow periods.

Details of the number of pick-ups, and their command areas and beneficiaries in the Tumkur District for the period 1991-92 to 1994-95, are given in Table 22. Table 23 shows typical construction dimensions of these structures.

Operation and Maintenance

The pick-ups are constructed by individual farmers, who are responsible for both the operation and maintenance of the structures. The primary maintenance requirement is that the structure remain impervious to minimize the possibility of dam failure.

Level of Involvement

The pick-ups are managed by the individual farmers who build, operate and maintain the structure. Government may be involved in the funding and/or initial sanctioning of the project site, and in the inspection of the dam. Mainly, governmental actions will be carried out by the local self-governing bodies involved.

TABLE 22. Pick-ups in the Tumkur District Constructed Under the Million Wells Scheme.

Division	Years
	1991-92	1992-93	1993-94	1994-95
Tumkur
Number of Pick-ups	15	3	10	18
Total cost($)	$31 750	$7500	$20 000	$37 000
Command area (ha)	136	33	89.5	Naa
Gubbi
Number of Pick-ups	22	6	20	10
Total cost ($)	$31 500	$10500	$48 750	$218 500
Command area (ha)	159	39	183	NA
Tiptur
Number of Pick-ups	21	16	12	3
Total cost ($)	$78 000	$57 500	$35 500	$8000
Command area (ha)	254	195.5	158	NA
Tutuvekere
Number of Pick-ups	7	14	3	11
Total cost ($)	$144500	$31 000	$10 500	$23 000
Command area (ha)	41	77	24	NA

^aNA = Data Not Available

TABLE 23. Typical Dimensions of a Coconut Pick-up.

Rock weir bund
Width	3.05m
Max. Height (from the basin)	1.83m
Total length of the pick-up	36.60 m
Side embarkment length	9.15m
Mud guide bunds
Height	0.75m
Length	61 m
Back water: Depth (max)	1.83m
Maximum width	91.5 m
Length	500 m

The rights of the farmer who has constructed the pick up are as follows: the farmer may make use of the silt accumulated behind the bund; the farmer may construct a storage tank and provide such tanks with a sump from which to pump water that has been conveyed to the tank from the pick-up (however, neither the farmer nor any other individual can directly pump water from the pickup); and, the farmer can raise bamboo, teak and other suitable species of tree on their katha bund (wingwalls) and along their periphery.

Costs

The costs incurred in the implementation of this technology are summarized in Tables 24 and 25.

TABLE 24. Capital Cost of Project Implementation.

Particulars	Years
	I	II	III	IV
Crude Jelly ($/power tiller load)	$1.50	$1.15	$1.75	$4.25
Stones and boulders ($/power tiller load)	$1.15	$1.00	$1.15	$3.15
Labour (days)	240	200	300	740
Empty cement bags ($)	$5.75	$0	$0	$5.75
Clay ($/power tiller load)	$1.50	$1.75	$2.15	-
Stone pillars ($)	$0.50	-	-	$0.50
Power tiller (days)	60	30	30	120

Effectiveness of the Technology

This technology augments available water resources by storing surface water and recharging groundwater. As shown in the data provided in Table 26, there was an observed recharge in six open wells as a result of infiltration from the coconut pick-ups from the second year onward.

This traditional technology is ideally suited for the local conditions prevailing in this region of India. In terms of costs, the pick-up is valued at about $7 000, based upon the nominal rates used by the government ($353/ha). However, by using locally available materials and using existing farm labour, the farmer actually spent $1 825 in constructing the Tumkur pickup. It is therefore important to create awareness of this technology amongst the farmers, and encourage local initiatives in its construction.

TABLE 25. Details of Expenditures Incurred.

Cost Element	Total Cost
Crude jelly ($2.15/load)	$ 32.25*
Stones and boulders ($4.25/load)	$ 471.75*
Clay (S1/load)	$ 159.00*
Labour ($0.50/day)	$ 317.50
Empty cement bags ($)	$ 5.75
Stone pillars ($1.15 each)	$ 18.40
Power tiller ($4.25/day)	$ 514.25
Miscellaneous	$ 15.10
Total	$1 534.00

*Imputed costs

Advantages

The principle benefits which may be derived from using this technology include:

· The availability of impounded water, the depth and extent of which depends upon the terrain, width and depth of the stream, and the duration of which depends upon the soil type, usage and frequency of rainfall/refilling.

· Enhanced groundwater recharge due to both vertical percolation and horizontal interflow, revitalizing percolation tanks, open tanks and tube wells; the recharging of open wells is almost immediate within a radius of up to one-half of a kilometre depending on soil structure and gradients.

The ponds created by the pick-ups serve as drinking water sources for livestock from 8 to 10 villages in the communities surrounding the pick-up. These ponds also serve as a common place for washing clothes and conducting religious ceremonies (Ganga Pooja); for seasoning wood and wooden poles by submerging them in water, which is a common practice; for retting coconut husks and agave leaves; and for other, similar activities. The waterbodies attract birds and serves as habitat for aquatic creatures, and can provide water for pisciculture. Agroforestry practices can be implemented along the periphery of the waterbody, which creates a microclimate that is more congenial for the growth of plants, including coconut and arecanut plants.

The pick-ups reduce the impacts of soil erosion and downstream siltation, while retaining silt that can be collected in the pick-ups and carted off to the coconut plantations during summer months to improve soil structure and fertility, and, in turn, increase their productivity. The pick-up structures can also serve as a vital link between villages, especially during the rainy season when travel may be restricted by flooding rivers.

In certain areas, seepage into percolation wells as a result of groundwater recharge from the pick-ups is used to irrigate coconut and arecanut gardens, other field crops like ragi and maize, and even paddy crops.

TABLE 26. Benefits Derived from the Use of Pick-ups.

Total area benefiteda
Left bank
Direct Benefit: Coconut plantation	20 acres
Indirect Benefit: Coconut plantation	15 acres
Direct Benefit: Arecanut plantation	5 acres
Indirect Benefit: Arecanut plantation	5 acres
Right bank
Direct Benefit: Coconut plantation	5 acres
Indirect Benefit: Coconut plantation	5 acres
Indirect Benefit: Paddy	1 acre
Indirect Benefit: Irrigated crops	3 acres
Number of open wells recharged (from 2nd year onwards)	6
Number of borehole wells recharged	3
Silt availability	50 tractor loads once in a yearb
Coconut yield has increased	2-3 times (50-60 nuts/palm/year)
	2 times (from 2-3 kg/palm/year to 5-6 kg/palm/year)

^a Direct Benefits include the plantations benefited by flooding as well as groundwater irrigation;
Indirect Benefits comprise the plantations benefited by groundwater recharge.
^b An additional benefit is the reduction of siltation downstream.

Disadvantages

Possible disadvantages include increased nuisance due to mosquitoes breeding in stagnant water that may collect upstream of the pick-up structures.

Further Development of the Technology

Based on the aforementioned observations, methods of involving the local people in planning and executing such projects is very important to achieving long lasting benefits from such ventures.

Information Sources

Gracy C.P., B.L. Chinanda, C.K. Jalajakshi, and K.H. Vedini 1995. Traditional Methods of Soil and Water Conservation - A Case of Coconut Pickups. In: Proceedings of the National Workshop on Traditional Water Management for Tanks and Ponds. Centre of Water Resources and Ocean Management, Anna University, Madras.

5.3 Use of reclaimed water - Hindustan petroleum corporation limited, India

Introduction

The Hindustan Petroleum Corporation Limited (HPCL) uses seawater for cooling and fire protection purposes at their refinery. The seawater is pumped, by means of pumps located in a salt water pump house situated on a jetty, through a 36-inch diameter cement-lined pipe, to the refinery. The refinery is switching over, in phases, from once through cooling systems to circulating cooling systems to minimize dredging frequency, effluent generation and interruptions to their operations due to pump failures. Concurrent with this change in cooling system operations, the Corporation plans to switch their cooling systems from seawater to reclaimed water from nearby sewage plants. Once this is achieved, the jetty pumps will be exclusively for fire protection service. The reasons for switching to reclaimed water for cooling purposes were principally due to changes in the pollution control regulations, and to operation and maintenance problems related to the use of the seawater.

Blow down from cooling towers, when using salt water for cooling purposes, is very high in total dissolved solids (TDS is more than 15%), and more frequent blow downs are required if the effluent from this process is to contain TDS at the level required to meet the Central Pollution Control Board's Minimal National Standards (the MINAS regulations). Use of reclaimed sewage for cooling enables the refinery to reduce the frequency of blow downs from the cooling towers and thereby reduce the volume of effluent requiring treatment to MINAS to manageable quantities.

Likewise, seawater places an undue strain on heat exchangers due to its high salt content. Switching to treated wastewater may be expected to improve the life of the heat exchangers. However, it is important that the wastewater be domestic in nature to ensure that it does not contain any industrial chemicals. Using reclaimed wastewater is expected to reduce the cooling system make-up water requirement from 4 500 m3/hour (or 108 000 m³/day) to about 625 m³/hour (or 15 000 m³/day).

Technical Description

The design of the project entailed extensive engineering evaluations to identify the most appropriate source from which to obtain the treated wastewater. These investigations considered not only the location and infra structural requirements for conveying the treated wastewater to the refinery, but also the quality of the effluents. Four different sites from which to obtain treated sewage were studied before deciding on a site near the Ghatkopar-Chembur fly-over. This site was chosen because the source of the wastewater was purely domestic in nature (whereas other sources had some industrial loading to the treatment works), of adequate volume (not less than 15 MLD throughout the year, with an average flow of 50 MLD), and had available space in which to site a pump house without causing any outside disturbance. Sewage obtained from this source would be pumped 5.4 km to a 15 MLD sewage reclamation plant at the HPCL factory (expandable to 23 MLD, if required). Of the three possible routes between the fly-over and the plant, the route along Chembur-Govandi Road, Maharishi Dayanand Saraswati Marg Road, Golf Club Road, and Koliwada-Kurla Road, through the RCF colony to the Ashish Theatre, and along Corridor Road to the HPCL refinery site was chosen for the rising main. This route was selected because it passed along wide roads with relatively little traffic where pipe-laying work will be easier and faster. This route also facilitates future maintenance. Cast iron pipes were selected for conveyance of the sewage because of their ability to withstand heavy external pressure and resist corrosion.

Tertiary treatment of the wastewater will be provided by chemical treatment of secondary treated sewage. An alum solution will be dosed in a chamber upstream of the flash mixers and conveyed to clari-flocculators for the removal of fine suspended matter and colloidal turbidity. Clear liquid overflows the weir at the top of the clari-flocculator and flows into the launder, while the particulate sludge is collected on the bottom of the clari-flocculator and conveyed to sludge sump. The clarified effluent from the launder is then routed to four twin bed rapid sand filters containing a layer of quartz sand and a layer of graded gravel. The under drainage system includes air blowers and water wash lines for back washing the filters. The filtered water will be pumped from a storage reservoir, routed through four identical ion-exchange softener units, and chlorinated prior to use as cooling water. Each softener unit will have adequate cation exchange capacity so that regeneration will not be required more frequently than once in 12 hours. The chlorination system will consist of two vacuum type chlorinators.

Extent of Use

The project is being implemented by HPCL.

Operation and Maintenance

The wastewater reclamation plant uses proven technologies for treating water and wastewater. No extraordinary requirements are anticipated. The primary operation and maintenance requirements include replenishment of chemicals, maintenance of pumps and dosing equipment, monitoring of inflow and outflow effluent quality, and general plant supervision. Skilled staff are required.

Level of Involvement

This technology is being implemented at the industry level.

Costs

The operation and maintenance costs are broken down into the costs of human resources, chemicals, energy, and related costs, including the repair and replacement of equipment. These costs are summarized in Tables 27 through 29.

TABLE 27. Annual Human Resources Costs.

Category	Cost per month ($)	Number of staff	Amount per year ($)
Superintendent	$150	1	$ 1 800
Operators	$120	10	$14400
Helper	$60	10	$ 7200
	Total		$23 400

TABLE 28. Annual Chemical Costs.

Chemical	Anticipated dosage (mg/l)	Quantity required for 15 MLDplant (kg/day)	Cost per kg ($/kg)	Total cost for 15 MLD planta ($)
Alum	20	300	$0.06	$ 18
Polyelectrolyte	1	15	$4.50	$ 68
Chlorine	5	75	$0.12	$ 9
Common salt	-	4330	$0.03	$131
	Total cost per day in $			$226
	Total cost per year in $			$82 730

^aFirst stage = 15 MLD,
Second stage = 30 MLD.

TABLE 29. Annual Operation and Maintenance Costs.

Operation and Maintenance Item	Total cost for 15 MLD plant ($/year)
Electricity
Conveying and treating sewage: 615 Kw or 14 750 Kwh @$0.03/Kwh	$178 000
Maintenance and repair
Civil engineering and hydraulic works @ 1 % of capital cost	$ 20 150
Mechanical and electrical works @ 2% of capital cost	$ 16 500
Depreciation
Civil engineering and hydraulic works @ 2% of capital cost	$ 40 300
Mechanical and electrical works @ 5% of capital cost	$ 41 450
Insurance
Insurance costs @ 0.5% of capital cost	$ 14 200
Property rental and other costs
Lease costs for siting a pumphouse on MCGB lands under the Ghatkopar-Chembur Flyover	$ 18200
Nominal cost of acquiring 23 MLD sewage from MCGB system	$ 1
Total Operation and Maintenance Costs	$328 801

TABLE 30. Total Operating Cost of the Treatment Plant.

Item	Annual operating cost for 15 MLD plant ($)	Annual operating cost for 30 MLD plant ($)
Manpower	$ 23 400	$ 23 400
Chemicals	$ 82 730	$165 460
Electricity	$178000	$297 000
Maintenance and Repair	$ 36 650	$ 54 400
Depreciation	$81750	$109000
Insurance	$14200	$18200
Property rental and Other expenses	$18201	$18201
Total	$434931	$685 661

From the Table 30, the annual operating cost per unit of flow of the 15 MLD plant will be $0.08/m³. The comparative cost of municipal freshwater supplied to industries in Bombay is $0.45/m³ in 1996. Hence, HPCL can achieve a substantial savings in operational expenditure in addition to the savings in freshwater achieved.

A breakdown of the capital and engineering costs of the various components of the project is given in Table 31.

TABLE 31. Capital and Engineering Costs of the Reclamation Project.

Item	Total Cost ($)
Pumphouse at Ghatkopar-Chembur Flyover	$ 240000
Force main	$1 130000
Sewage water reclamation plant	$1350000
Off site facilities like storage and pumping facilities at Refinery	$ 523000
MCGB supervision fee (Tentatively estimated at 15% of the total cost of work done on municipal roads)	$ 153000
Architectural design fees including detailed engineering and other owner expenses during construction phase (9% of total cost)	$ 305500
Engineering fees and consultancies (10% of total cost)	$ 373000
Design change allowance and contingencies	$ 303000
TOTAL	$4 377 500

Effectiveness of the Technology

The use of reclaimed wastewater is expected to reduce the cooling makeup water requirement from 4 500 m³/hr or 108 000 m³/day to about 625 m³/hr or 15 000 m³/day, with a concommitant cost savings over acquiring this makeup water from municipal sources.

Advantages

Reclamation of sewage for cooling water use has three advantages for HPCL; namely:

· the problem of high TDS that arises from the use of seawater is eliminated

· the demand for freshwater from the municipal supply is reduced, making more water from municipal sources available for use as drinking water in Bombay.

· the cost of municipal water to HPCL is reduced, providing a financial advantage to the Corporation in light of an increasing tariff structure for freshwater supplied to industrial users in Bombay.

Disadvantages

This technology requires a significant capital expenditure and is technology intensive, requiring skilled staff to install, operate and maintain.

Future Development of the Technology

The technology of sewage reclamation is an established technology that may be attractive to industries like HPCL who have large water requirements and who depend on (diminishing) water supplies from municipal corporations. The technology is transferable and can be used by other industries.

Information Sources

AIC Watson, Consulting Engineers, Bombay, India.

Hindustan Petroleum Corporation Limited (HPCL), India.

5.4 Reclaimed city sewage as industrial water - Madras fertilizers limited, Madras, India

Introduction

The Madras Metropolitan area, with scant rainfall, no river sources, and no major nearby watersheds, has always been chronically short of freshwater. The demand on the existing scarce sources has increased substantially due to increases in population and industrial development. Lately, the problem of water availability has reached crisis levels and has resulted in several stoppages of water supplies to industries, leading to heavy losses in production and related financial losses to the industries located in this area. Madras Fertilizers Limited (MFL) faced such situations in 1983 and, again, in 1987, prompting MFL to explore alternative sources of water such as desalinated seawater, seawater and treated sewage for meeting its process cooling water supply needs.

The Company's total 20.25 MLD water requirement had been supplied by the Madras Metropolitan Water Supply and Sewerage Board (MMWSSB) from two aquifer sources located 20 km away from MFL at Panjetti and Tamarapakkam. Of the total water consumed, 13.7 MLD were required as makeup cooling water, with the balance used in the production process and for other general uses. Of the options available to the Company for supplementing or replacing the municipal water sources, the Company decided to reclaim water from city sewage using advanced wastewater treatment technologies, followed by reverse osmosis (RO) as an additional purification step. Installation of the facility was completed by 1991. This treatment plant, one of the few units in the world treating city sewage for industrial use, has freed about 13.7 MLD of potable water for domestic use in the City.

Technical Description

The MFL reclamation plant processes include wastewater treatment through tertiary treatment using an activated sludge process, followed by excess lime addition, ammonia stripping, recarbonation, chlorination, multimedia filtration, activated carbon filtration, cartridge filtration, and reverse osmosis filtration using thin film polyamide membranes. In the primary treatment phase, the bulk of the suspended solids is removed by coarse mesh screens and in primary clarifiers. At this point, the BOD has been reduced from 350 ppm to 50 ppm. In the secondary treatment phase, the effluent is passed through a trickling filter (biofilter) into an aerated lagoon. The biomass formed in the aerated lagoon is removed in the secondary clarifier as sludge. The sludge is recirculated back to primary clarifiers to maintain bacterial population in the biofilter. The waste sludge from the plant is removed as underflow from the primary clarifier, digested biologically, and disposed of. Analysis of the water after primary and secondary treatment showed that impurities such as ammonia-nitrogen, dissolved phosphorus, silica and BOD remain too high for use in the cooling system. Therefore, the overflow from the secondary clarifier is to be sent to the tertiary treatment phase for further physciochemical treatment.

The secondarily treated effluent is transferred to a receiving lagoon, from which it is pumped to two aeration tanks equipped with four 25 HP fixed surface aerators. The aerated sewage effluent then flows into a biomass clarifier where the biological sludge formed during aeration is settled out. The bulk of the biological sludge is pumped back to aeration tank by sludge transfer pumps to maintain the Mixed Liquor Suspended Solids (MLSS) of 3 000 mg/l. The overflow from the bioclarifier is pumped to the lime softener, where ferric coagulant and lime are added along with a polyelectrolyte solution. The Milk of Lime, or calcium hydroxide solution, is added in sufficient quantities to maintain the pH between 10.8 and 11.5 to facilitate ammonia stripping. The lime softener overflow is passed through five gravity sand filter beds to trap and reduce the physical carryover of lime and calcium carbonate from softener, so that they do not foul the ammonia strippers. These sand filters are periodically backwashed using water recycled to the lime softener. The filtered water is pumped to first-stage and second-stage, counter-current flow ammonia strippers consisting of two cells in each stage. These are similar to cooling tower cells. Effluent is sprayed from the top of the towers while air is sucked into the bottom of the towers by induced draft fans located at the tops of the towers. In the process of air-liquid contact, free ammonia is removed from the liquid into the air. The atmospheric carbon dioxide also partially neutralizes the Ca(OH)₂ in the water, resulting in a slight drop in the pH during this process. A caustic soda solution is added after first stage ammonia stripping to restore the pH level. From the second stage ammonia strippers, the effluent is pumped to first stage carbonation tower in which CO₂ is injected into the effluent to reduce the pH to 9.3. The precipitated CaCO₃ is removed in the calcium carbonate clarifier, and the overflow from the clarifier flows to the second stage carbonation tower, in which the pH is further reduced 8.3 with sulphuric acid. Following the second stage carbonation, the treated effluent is acidified to pH 7 and chlorinated before it is sent to the tertiary treated water storage.

The excess sludge from the bioclarifier underflow is disposed off in sludge drying beds operated on a 7 day drying cycle. Water from the sludge drying beds is recirculated into inlet lagoon. The sludge from the underflow of calcium carbonate clarifier and lime softener is thickened to between 7% and 10% solids, and dewatered on vacuum belt filters prior to disposal. The water separated from the sludge by this system is also recycled to the plant.

Though undesirable constituents like BOD, hardness, ammonia, etc., are removed by tertiary treatment, the total dissolved solids (TDS) content of the treated water remains higher than that of well water. High TDS concentrations result in higher rates of water consumption, increased corrosion in the recirculating water system, and higher chemical dosing costs to keep corrosion and sealing problems in check. Thus, TDS has to be reduced to lower levels to ensure the smooth, uninterrupted operation of the cooling water system. The removal of TDS will also reduce the frequency of blow downs and result in both a saving of water and costly cooling water treatment chemicals lost in the blow down process. Two alternative technologies were considered viable for reducing the salinity of the treated water; namely, conventional demineralization by ion exchange (IEDM) resins which must be regenerated periodically by acid/alkali treatments, and reverse osmosis (RO). The latter was considered to be the more convenient alternative.

The MFL cooling water system is designed to operate over four to five cycles between blow downs using a makeup water containing up to 300 mg/l chloride. Because the RO permeate (water that has passed through the filter membrane) has a lower salinity, part of the feed water to the RO is bypassed and blended with the permeate to achieve the operating salinity of 300 mg/l chloride. The portion of the treated water which is to be subjected to RO filtration is further treated in the chemical pretreatment section to lower the pH. Sodium hexametaphosphate and sodium bisulphate are added to inhibit scaling by CaS0₄ and for chlorine removal, respectively. This pre treated water is filtered through polypropylene micron cartridge filters, and pumped to the RO unit by high pressure pumps. The RO unit is laid out in multiple streams and each of these streams has three brine stages. The brine, or rejected water, from one stage passes, through a common header, to the next stage to recover the maximum quantity of permeate from the feed water. Rejected water from all RO streams is collected and sent for effluent disposal. The RO unit has been designed for a recovery of 75% of the feed water as permeate.

Extent of Use

As noted, MFL considered the following alternatives in detail to meet its process cooling requirements: desalination of seawater, direct cooling with seawater, indirect cooling with seawater, and use of sewage effluent after suitable treatment. The seawater desalination alternative was considered to be too power/energy intensive as well as capital intensive. The cost of water produced by this technology was estimated to be very high. Direct cooling with seawater was considered to involve the complete replacement of existing admiralty brass fittings used within process water heat exchangers with titanium or cupronickel fittings. This would have required heavy investment and amounted to revamping the entire plant, involving considerable time loss as well as production losses. In indirect cooling, process water heat is transferred to a treated intermediary freshwater which, in turn, is cooled by seawater in a large sized titanium plate exchanger. The disadvantages of this system are its high capital investment cost and anticipated delay in implementation of the project due to long delivery periods for items such as the plate exchanges. (For both indirect and direct seawater cooling alternatives, seawater must be filtered and chlorinated before transfer to MFL from the nearby Ennore Estuary through large diameter pipelines.) In contrast, the sewage treatment project was estimated to be able to be completed within 14 months with a lower level of capital investment as well as lower operating costs. Hence, the use of reclaimed water was considered to result in the least level of disruption to plant operations and the lowest cost.

Operation and Maintenance

Qualified chemical engineers are required to operate and maintain a reverse osmosis unit. Skilled operators are also required to operate and maintain a tertiary wastewater treatment plant.

In spite of the elaborate pretreatment of the reclaimed water, the membranes in the RO unit are likely to become fouled after a period of operation, resulting in a reduction in permeate yield. At this stage, the membrane must be cleaned to remove the fouling using proprietary chemicals supplied by the manufacturers. However, over about a three year period, there is slow and progressive loss of membrane efficiency due to a certain amount of irreversible fouling and degradation from various causes, and the membranes must be replaced.

Level of Involvement

The predominant involvement in this project was by the industry. However, there was significant participation by the MMWSSB and government in specific phases of the project.

Costs

The capital cost of the entire project is estimated at $18 million.

Effectiveness of the Technology

Due to the sewage reclamation scheme, 13.7 million litres of potable water, previously supplied each day to MFL from the Metro water treatment plant, has been redirected to domestic use in the City.

Advantages

The advantage of reclaiming water from treated sewage for industrial use is that it is more economical than the other options suggested. Similarly, the use of RO as the final polishing stage has an edge over the Ion Exchange Demineralization (IEDM) technology because the RO unit is geographically compact, with its components situated close to each other, making operational control of the plant much easier. The RO unit also will run over longer periods without interruption, minimizing the need for constant care and reducing operational errors. The operation of the RO unit is more convenient, less complex and cumbersome, and less prone to the possibility of errors than IEDM techniques. Maintenance is also easy, and the replacement of filter cartridges and membranes can be quickly carried out without much effort.

In terms of operating costs, the RO unit requires only small quantities of acid and sodium bisulphite, etc., and the RO unit can cope with increases in salinity without any significant adverse effect on the product quality or cost. Annual operating costs of the RO unit may be as much as 40% lower than those of alternative technologies which produce water of the same quality and quantity.

Disadvantages

The major disadvantages of RO are the high installation cost of the system as well as its high energy costs, since its rate of power consumption is very high.

Further Development of the Technology

It often requires a crisis to provoke the reuse of such a valuable water resource as sewage for industrial activities. One important aspect of the sophisticated tertiary treatment plant that remains to be addressed is the high level of nitrates in the effluent (10 to 12 mg/l as nitrate). This is due to nitrification occurring within the activated sludge process, and may affect the longevity of the RO plant. It is therefore suggested that a combined carbon oxidation and nitrification step be developed for use in the activated sludge treatment process.

Information Sources

Rajappa, M.S. 1990. Reclaimed City Sewage as Industrial Water, Journal of Indian Water Works Association, Jan-March, pp 95-100.

5.5 Rainwater harvesting - the Thai rainwater jar

Introduction

Thailand's National Jar Programme, to supply of clean drinking water to rural areas, was launched in response to the United Nations' Water Supply and Sanitation Decade (1981-1990). The Program's objective was to promote the use of jars in rural households as a means of supplying clean drinking water. User participation was encouraged, although, early in the program, rural poverty was endemic and villagers could only provide in-kind labour. Government subsidized the cost of research (to find suitable designs and construction techniques), training, and construction materials. Some jars were provided without cost in cases of extreme need, although this was not the intent of the Program. While private sector involvement in the Programme was not planned in the initial project design, commercial production of rainwater jars eventually replaced the Government-subsidized jars, to the benefit of everyone concerned. Such privatisation continues, and Government, now, is no longer involved in jar production.

As the name implies, the Programme was national. It covered all regions of Thailand, including the south which receives rainfall almost throughout the year. Not surprisingly, however, rainfall jars are not as widely used in the south as in other regions. Culturally, the jars are not new to Thailand, and, hence, are well-accepted by users. Small-sized jars (0.5 m³) have been used in households for generations without Government intervention. However, the National Jar Programme promoted the use of large jars (2 m³) as the most cost effective size. In line with traditional practice, the 2 m³ jars were designed to be household-oriented.

Technical Description

Jar construction techniques are similar to ferrocement tank construction techniques. The shape of the jar resembles a sphere, thus offering the most efficient use of materials in term of strength per unit of mass. An empty 2 m³ jar is transportable, and can be hauled onto a pickup truck by two men using simple, locally available equipment. The construction technique is simple and compatible with locally available skills. The technology has performed well as evidenced by its acceptance by the private sector; commercial jar manufacturers can be seen along highways throughout the country. Most rural households now have at least two jars, the service life of which is estimated to be 20 years.

Extent of Use

Before the technology was introduced, research was conducted to find the optimum size and most suitable construction technique for the jars. Their introduction was undertaken through various Government-supported, village jar construction projects, and the King's 60th birthday (5 December 1988) was used as a milestone for targeting achievement. Mass media played an important role in publicizing and promoting the use of the rainwater jars. The project was subject to some initial skepticism from the mass media and some public figures, but this was silenced by widespread acceptance of the jars by rural households. There was also some corruption involving the Government funds provided for village jar construction, which resulted in the production of some substandard jars. Leakage and breakage were common in such cases. However, shifting of manufacture of the jars from Government programmes to the private sector eliminated this corruption.

Operation and Maintenance

Similar to most household-oriented commodities, such as televisions and appliances, rainwater jars are operated and maintained by their owners. The producers of the jars (formerly Government and currently commercial jar manufacturers) have no role beyond the initial sale of the product. Operation and maintenance problems include personal injuries sustained during cleaning, breakage of the jars due to accidents, and contamination resulting from animals licking the discharge taps, using unsuitable roofing and guttering materials, or neglecting to use the jar lids.

Level of Involvement

Table 32 presents a summary of the levels of involvement by parties concerned with the production, promotion, installation and operation of rainwater jars.

TABLE 32. Summary of Roles and Responsibilities of Parties Involved in Rainwater Jar Implementation.

PARTIES	ROLES IN JAR TECHNOLOGY
Government	Initiating and fostering the introduction of jars (At present this role is over)
Private sector	Supplying commercial jars to consumers (As producers, this role is continuing)
Community	Producing jars during the introductory period (At present this role is over)
Households	Operating and maintaining the jars (As beneficiaries, this role is continuing)

Costs

The capital costs of a rainwater jar are summarized in Table 33. Based upon this figure, the average cost of water supplied using this technology is $1.10/m³/year.

TABLE 33. Capital Cost of a 2 m³ Rainwater Jar

Rainwater Jar Component	Cost ($)
2 m3 Rainwater jar	$34.50
Cover	$1.75
Transportation charges: 1 or 2 jars @ $0.25/km, over 20 km on average	$5.00
Installation of guttering	$2.15
TOTAL	$43.40

The operation and maintenance costs of a rainwater jar are summarized in Table 34. The costs are estimated based upon the annual cost of operating and maintaining two rainwater jars, with the labour costs estimated at the Government's basic minimum wage of $0.65/hr.

TABLE 34. Operation and Maintenance Cost of a 2 m³ Rainwater Jar.

Rainwater Jar Component	Cost ($)
Refilling with rainwater (12 hourly)	$7.75
Use of the rainwater (0.25 hr/day × 4 months)	$19.35
Cleaning (4 hours)	$2.50
TOTAL	$29.60

Including both the capital and operation and maintenance costs, then, a typical household will spend $8.50/m³/year for clean drinking water using jars. The alternative source of drinking water is bottled water, popular in urban areas, which may be purchased at a cost of about $0.65/litre, or $645.00/m³ - more than 75 times more expensive than jar water. This cost differential may be another reason for the jars' popularity. Unlike the rainwater jars, the plastic containers used for bottled water are now causing serious environmental pollution.

Effectiveness of the Technology

According to a 1992 review by the National Economic and Social Development Board (NESDB), the numbers of 2 m³ jars in use in Thailand increased from virtually none in 1985 to nearly 8 million in 1992. This increase was partially due to the Government's National Jar Programme, but mostly due to the willing adoption of the technology but the public and to the widespread promotion of the technology by the commercial sector. Government intervention is no longer necessary.

Surprisingly, in the second half of the UN Water Supply and Sanitation Decade, the sanitation index, compiled from data on public health problems such as the frequency of incidences of diarrhea, increased despite the introduction of the jars and the wider availability of clean drinking water. The success of the National Jar Programme prompted the Government to introduce a similar national programme to improve sanitation, the National Latrine Programme.

Advantages

Local politicians liked the Government's Jar Programme and used the jars as banners for political campaigning, although the jars are no longer connected to politics. The implementation of this technology is totally regulated by economics and free-market mechanisms due to widespread private sector involvement.

Technically, jars have many advantages, including preventing the negative impacts of mosquitoes, which can breed in open water storages and other areas of standing water. The jars also cool households to a certain extent, and there is no longer the need for users to spend time and effort fetching water from beyond the household perimeter. Jars also reduce soil erosion as they intercept rainwater, running off the roof, before it reaches the ground.

Disadvantages

Disadvantages of this technology include the space taken up by jars within households. The jars may also become breeding places for mosquitoes if the containers are not kept closed. In space conscious households, a rainwater tank is preferred over the jars. (Rainwater tanks are a similar technology to the jars except that the tanks are taller and unmovable.) Corruption in the jar programme was endemic at the time the 2 m³ jars were introduced.

Further Development of the Technology

Rainwater jars are successful in the rural areas of Thailand because the technology is simple, inexpensive and understandable to a majority of the rural population. However, this success depended on user and private sector involvement. Success also depends upon other factors; rainwater jars are not suitable everywhere. For rainwater jars to be successful there must be sufficient rainfall distributed throughout the year. Roofing materials are also important considerations as they can negatively affect the quality of water collected. The jars themselves must be transportable without breakage from the manufacturing sites to the consumers. For this reason, ferrocement jars were found to offer advantages in terms of both robustness and mass; however, if cement is expensive, use of rainwater jars may not be feasible. The optimum size of the jars is also dependent on the above considerations. Finally, the potential environmental impacts arising from rainwater jar use must be assessed to avoid solving one (water supply) problem but creating another (public health) problem. To this end, user information campaigns should be undertaken to alert users to the dangers of spreading malaria and dengue fever through the improper use of jars.

Information Sources

Contacts

Dr. Sacha Sethaputra, Associate Professor, Water Resources and Environment Institute, Faculty of Engineering, Khon Kaen University, Tel./fax: 043 241 202; E-mail: [email protected].

Dr. Sanguan Patamatamkul Associate Professor, Water Resources and Environment Institute, Faculty of Engineering, Khon Kaen University, Tel./fax: 043 241 202; E-mail: [email protected].

Mr. Junlajit Sawaengphet, Researcher, Water Resources and Environment Institute, Faculty of Engineering, Khon Kaen University, Tel./fax: 043 241 202; E-mail: [email protected].

Dr. Nalinee Tuntuwanit, Researcher, Research and Development Institute, Khon Kaen University, Tel. 043 244 506, 238 383, fax: 043 244 418.

Ms. Tongtip S., Researcher, Research and Development Institute, Khon Kaen University, Tel. 043 244 506, 238 383, fax: 043 244 418.

Ms. Pacharin L., Researcher, Research and Development Institute, Khon Kaen University, Tel. 043 244 506, 238 383, fax: 043 244 418.

Ms. Sinee Chuangcham, Researcher, Research and Development Institute, Khon Kaen University, Tel. 043 244 506, 238 383, fax: 043 244 418.

Bibliography

Department of Health s.d. Manual for Caretakers of Village Pipe Water Supply Systems (Medium and Small Sizes). Rural Water Supply Division, Department of Health, Bangkok, Thailand 2535.

Department of Health s.d. Manual for Caretakers of Village Pipe Water Supply Systems. Rural Water Supply Division, Department of Health, Bangkok, Thailand 2535.

Department of Local Administration 1987. People's Volunteer Weir Program for Small Water Resources Development. Ministry of Interior, Bangkok, Thailand.

NESDB [National Economic and Social Development Board] 1992. Manual for Preparation of Master Plan for Provision of Drinking and Domestic Water for Villages in Each Province, NESDB, Bangkok, Thailand.

NESDB [National Economic and Social Development Board] 1992. Status of Drinking and Domestic Water in Rural Areas. NESDB Division of Rural Development Coordination, Bangkok, Thailand.

Office of Public Health s.d. Manual for Management of Village Pipe Water Supply Systems. Sanitary and Environmental Health Division, Office of Public Health, Chiangrai, Thailand 2535.

Thongtip, S., L. Pacharin, and K. Wichien 1995. Esan Women and Water Management, Research and Development Institute, Khon Kaen University, Thailand (in Thai).

Water Resources and Environment Institute 1986. Manual of Weir Construction. The KKU-NZ Weir Project Report, Khon Kaen University, Thailand (in Thai; English, Laos and Cambodian translations available).

Water Resources and Environment Institute 1991. Small Scale Water Resources: Clean Water and Sanitation. Thai- German Self-Help Training Project Report, Khon Kaen University, Thailand (in Thai).

Water Resources and Environment Institute 1991. Manual of Small Weir Design. Thai-NZ Small Watershed Development Project Report, Khon Kaen University, Thailand (in Thai).

Water Resources and Environment Institute 1991. Manual for Construction of Farm Pond. That-German Self-Help Training Project Report, Khon Kaen University, Thailand (in Thai).

Water Resources and Environment Institute 1991. Manual for Construction of Impact Well. Thai-German Self-Help Training Project Report, Khon Kaen University, Thailand (in Thai).

5.6 Daungha rainwater collection water supply project, Nepal

Introduction

Rainwater harvesting is an old practice in Nepal. People have been collecting rainwater for washing clothes and utensils, and for watering animals, for years. However, most of the people in the rural communities will try to avoid using water that has been stored overnight for drinking. They believe that the stored water is stale compared to flowing water. Thus, the practice of using rainwater catchment systems (RWCS) to supply drinking water (and water for other domestic uses, where possible) is of fairly recent origin.

The Gulmi District is one of 75 districts in Nepal and lies in the hill region in the western part of the country. Its topography ranges from 600 m to 3 000 m above sea level, and its climate ranges from a warm to a cool temperate climate, depending upon the altitude and the presence of deciduous monsoon forest. The Gulmi District is also one of 15 districts included in the Western Development Region. There are 79 villages in this District. Daungha is one of these villages, situated about 26 km southeast of the District Headquarters at Tamghas. The nearest roadhead is at Lumchha Hardeneta, which has a 25 km earthen road link with Tamghas, and a 50 km earthen road link with Tansen via Ridee Bazar. The Village of Daungha, administered by the Village Development Committee (VDC), is situated at an altitude of between 785 m and 1 350 m. There are three springs in the vicinity of the Village:

a. Hingaha Mul, Q = 0.85 lps, elevation 408 m, Ward no. 1

b. Nishi Mul, Q = 0.053 lps, elevation 885 m, Ward no. 5

c. Dharapani, Chinne and Kayanko Kunchnir Mul, Q = 0.08 lps, elevation 855, Ward no. 5

These springs are used for domestic purposes by about 1 500 people in about 150 households in Ward nos. 1, 5 and 6. People spend about 4 to 5 hours per day fetching water from these springs. The remaining population of the Village, located in other areas, face severe hardships in fetching water, as the few other available springs are not easily accessible. Due to the lack of other surface water resources, the Village has adopted rainwater harvesting as the most suitable technology for meeting the demand for freshwater.

The District Water Supply Office (DWSO) of Gulmi has been the lead agency concerned with the introduction of rainwater harvesting, and has constructed four ferrocement storage tanks, each with a capacity of 20 m³, during fiscal year 2046-47 (1989-90). A total of eleven tanks have been constructed through fiscal year 1994-95. Over 300 students and teachers, and more than 250 other people, have benefited from these construction projects.

Technical Description

Rainwater is collected from the rooftops of the buildings within the Village using corrugated galvanized iron sheeting as roofing materials. A gutter constructed of a half cut HDPE pipe and HDPE downpipe are used for collecting the rainwater in a storage tank. The storage tanks are 20 m³ ferrocement tanks, some of which are fitted with separate tapstands.

Extent of Use

The rainwater harvesting system was introduced in Daungha during the fiscal year 2045-46 (1988-89). As a pilot-scale project, one 20 m³ ferrocement tank was built to collect water from the roof of the middle school. This system helped to meet the drinking water demands of about 300 students and teachers at the school. The success of this system encouraged the villagers to build additional systems, and three more 20 m³ tanks were installed during 1989-90 (one additional tank at the middle school, one at the VDC Office, and one at the Mohare Primary School). The interest and active participation of the villagers have helped to promote the use of rainwater harvesting systems. Seven further storage tanks have been constructed and there are now eleven ferrocement tanks for rainwater storage in the Village.

Operation and Maintenance

Operation and maintenance requirements of this technology include the regular cleaning of the rooftops and gutters, the frequent cleaning of the storage tanks, and the periodic inspection of the gutters, feeder pipes and valve chambers to detect leakage. These tasks have been handed over to the users committee, who bear the overall responsibilities for the operation and maintenance of the systems. Required works that are beyond the capacities and means of the users committee are carried out by the DWSO.

Level of Involvement

Both the community and the Government have been involved in this project.

Costs

The total cost of the project was $24620, or $121 per capita. The project was financed through a cost sharing arrangement with His Majesty's Government providing $22560 and the Village providing $2060. The Village contribution was primary used for financing the cutting and back filling of trenches used to contain the piping that conveys the water from the rooftops to the storage tanks. The present rainwater harvesting system provides a total volume of 1224 l/day. The cost of a 20 m³ ferrocement tank is $2000. Although the operation and maintenance cost of the system is negligible, the capital cost is too high for individual households and a rural community to invest independently in such a system.

Effectiveness of the Technology

A total of 183 m³ of rainwater is collected annually in the storage tanks from the 160 m² rooftop catchment area in Daungha. Assuming the average rate of water consumption, for drinking purposes only, is 73 m³/year, this system can provide sufficient water to sustain 34 people. The ability of the rainwater harvesting scheme to service Village needs, shown in Table 35, was estimated on the following basis. It was assumed that the available catchment area was 160 m² (the combined area of the rooftops of 5 houses, each 8 m × 4 m), and that 75% of the total rainfall would be available for potential storage in the 20 m³ storage tank (rainfall of less than 20 mm/month was not considered to contribute to the total rainfall available for storage). It was further assumed that the maximum monthly rate of consumption of water for drinking purposes was 6.12 m³/person. Over the design period of 10 years, a 2% annual rate of growth in population from the design population of 28 persons (using the relationship pn = pn (1+r)") would result in a total population served 34 persons.

TABLE 35. Indicative Rainwater Collection at Daungha".

Month	Total rainfall (nun)	Catchment (m2)	Quantity of water entering the tank (m3) (75% of rainfall)	Consumption (m3)	Quantity of water in the tank at the end of the month
August	312.33	160	37.48	6.12	20.00
September	103.07	160	12.37	6.12	20.00
October	67.93	160	8.15	6.12	20.00
November	14.33	160	-	6.12	13.88
December	67.70	160	8.12	6.12	15.88
January	11.67	160	-	6.12	9.76
February	27.87	160	3.34	6.12	6.98
March	15.80	160	-	6.12	0.86
April	72.13	160	8.66	6.12	3.40
May	90.40	160	10.85	6.12	8.13
June	461.73	160	55.40	6.12	20.00
July	319.60	160	38.35	6.12	20.00

Advantages

The main advantage of this project is the time saved in fetching water, which may be utilized for other economic activities. Women especially benefit by having more free time for child care, social activity and income generation. Rainwater also has the advantage that it is considered to be free of contamination.

Disadvantages

The disadvantage of this technology is its high capital cost to implement.

TABLE 36. Monthly Precipitation at Ridee Bazar, Gulmi District, Nepal.

Month	Year				Average
	1987	1988	1989	1990
January	2.2	0.0	106.2	0.0	27.10
February	11.1	45.4	17.6	43.8	29.48
March	0.0	34.3	24.2	126.0	46.13
April	35.6	51.9	0.0	27.6	28.77
May	132.8	117.2	89.2	51.8	97.75
June	216.4	104.2	195.6	197.9	178.53
July	472.2	558.2	494.1	550.9	518.85
August	285.7	547.9	271.2	311.8	354.15
September	18.7	135.5	107.2	83.7	86.28
October	134.7	0.0	2.3	21.6	39.65
November	0.0	0.0	18.8	0.0	4.7
December	19.1	71.6	4.3	10.0	26.25
Annual	1328.5	1666.2	1330.7	1425.1	1437.64
Number of Rainy Days	66	78	69	74	72

Source: HMG/DHM 1992. Precipitation Records of Nepal, DHM: Ridee Bazar, Gulmi District: Elevation, 442 m

TABLE 37. Storage Tank Size Determination

Month	Rainwater Available (Q),m3	Demand (D),m3	Difference (Q-D),m3	Cumulative Difference (Q-D), m3
January	1.08	4.2	-3.22	-3.22
February	1.16	4.2	-3.04	-6.26
March	1.84	4.2	-2.36	-8.62
April	1.12	4.2	-3.08	-11.70
May	3.88	4.2	-0.32	-12.02 (T)
June	7.12	4.2	2.92	-9.10
July	20.75	4.2	16.55	7.45
August	14.16	4.2	9.96	17.41 (P)
September	3.44	4.2	-0.76	16.65
October	1.56	4.2	-2.64	14.01
November	0.16	4.2	-4.04	9.97
December	1.04	4.2	-3.16	6.81
Annual Total	57.31	50.4	-	-

Further Development of the Technology

Although rainwater is generally considered free of contamination, requiring little or no treatment prior to potable use, the roofs and gutters used to collect the rainwater need to be regularly cleaned, and the rainwater flowing off the roof at the beginning of rainy season should not be collected in the tank. While roofs are commonly used as catchment, ground catchments have the advantage of providing larger surface areas enabling greater volume of water to be collected. Ground catchments also are cheaper to construct. However, the use of ground catchments in Nepal is rare due to the limited availability of suitable land. Flat roofs with tiles or plastered concrete may be used, with floor traps instead of gutters, but sloped roofs are better as they are accessible for cleaning and repair, and the rainwater has less chance of being contaminated. Asbestos cement roofing and sheet metal roofing coated with lead based-paints should be avoided, as they may be dangerous to human health.

The storage tank is the most expensive part of any RWCS. The method used to determine the most appropriate storage capacity for any given locality, and the optimal size of catchment area needed to provide a reliable supply of rainwater for storage, will critically affect both the cost of implementing this technology and the amount of water available for use. In order to determine the potential rainwater supply for a given catchment, reliable rainfall data (mean annual rainfall and its distribution) are required for a period of at least 20 years.

Information Sources

Mr. I. Sainju, Civil Engineer, Department of Civil Aviation, Maintenance Branch, Tribhuvan International Airport, Kathmandu, Nepal.

Mr. R.B. Tamang, Department of Civil Aviation, Repeater Station, Phulchoki, Lalitpur, Nepal.

5.7 Conjunctive use of surface and groundwater - Krishna Delta, India

Introduction

In cases where a river system has been exploited to the maximum extent, and where large, unmet demands for water continue to exist, it is often necessary to exploit groundwater resources wherever they exist. However, in the lower reaches of the system, it is also likely that seawater intrusion will reduce the potential exploitation of groundwater resources in the deltaic reaches of the system. In such situations, mixing of groundwater with surface water can be used to augment water supplies.

The Krishna River flows through the states of Maharashtra, Karnataka and Andhra Pradesh (AP), and has reached this state of maximum surface water exploitation. In accordance with the Bachawat Award for the distribution of river waters, Andhra Pradesh State has an allocation of 22653 million m³, most of which is currently being exploited or has been earmarked for exploitation in the foreseeable future, leaving some areas of Rayalasema without enough water to satisfy the minimum requirements. In view of this, the Andhra Pradesh State Government has commissioned the Telugu Ganga Project, a prerequisite for which is the conservation of the waters of the Krishna River upstream of Nagarjuna Sagar Reservoir. The use of groundwater in conjunction with surface water resources has been proposed as part of these conservation measures. According to information published by Andhra Pradesh State Irrigation Development Corporation (APSIDC), the utilizable groundwater resources of the Krishna Delta are 4 568 million m³, against an annual net utilization of 287 million m³. Hence there is enough scope for utilization of groundwater in the delta provided it is blended with available surface water to achieve an acceptable quality for, primarily, agricultural use.

Technical Description

In order to meet the minimum water requirements of the Delta area, the quality of groundwater and surface water in Krishna Delta ayacut was considered in order to determine an appropriate blend of groundwater and canal water to support their conjunctive use. The quality of groundwater along the coastline is generally poor due to the intrusion of seawater into the coastal aquifers. Chloride concentrations are generally found to be in the range of 85 to 845 ppm. For this reason, crop irrigation mainly depends on canal waters as the primary water source. Two methods of mixing surface and ground waters were investigated; namely, supplying surface and ground waters separately for alternate waterings in the required proportions, and directly blending surface and ground waters by pumping groundwater into the canals.

Extent of Use

APSIDC collected ground and surface water samples at Tenali, Duggirala, and Pedavadlapudi in the Krishna Western Division, at Nidumole, Gudur and Pamarru in the Krishna Central Division, and at Eluru, Gudlavalleru and Mudinepalli in the Krishna Eastern Division, and analysed the samples for Total Dissolved Solids (TDS) and chloride concentrations, hardness and Electrical Conductivity (EC). Selected results are shown in Table 38. These analyses, and related soil samples, collected at root zone depth, suggested that the conjunctive use of surface and ground waters was possible, as shown in Table 38, and that concerns regarding salination of the soils were unfounded. Insignificant concentrations of chlorides were present in the soil, probably due to leaching by rainwaters during the Khan/season. The import of this finding was that no allowance need be made for using additional canal waters to "sweeten" the soils by leaching excess salt from the soil profile.

TABLE 38. Groundwater Quality in the Krishna Delta^a.

Collection Point	Chloride (ppm)	Total Dissolved Solids (ppm)	Hardness (ppm)
Groundwater
Tenali	145	879	210
Duggirala	140	916	160
Pedavadlapudi	130	1346	175
Nidumolu	85	842	135
Gudur	60	1 044	300
Pamarru	845	4916	730
Eluru	240	1253	210
Gudlavallaru	70	1 160	145
Mudinepalli	250	941	150
Surface Water
Tenali	55	625	65
Duggirala	55	631	55
Pedavadlapudi	55	597	55
Nidumolu	60	677	130
Gudur	55	783	125
Pamarru	50	759	139
Eluru	60	704	90
Gudlavallaru	50	669	115
Mudinepalli	50	652	135

^a In all the above samples, sulphate concentrations were found to be below the limit of detection, and the value of electrical conductivity was less than 1 000 microMhos/cm.

TABLE 39. Water Quality Standards for Irrigation Water.

Class of Water	Electrical Conductivity (mhos/cm)	TDS (ppm)	Chloride (ppm)	Sulphate (ppm)	Boron (ppm)	Range of Hardness as CaCO3 (ppm)	Remarks
I	0-1000	0-700	0-142	0-192	0-0.5	0-55	Excellent to good
II	1000-3000	700-2000	142-355	190-480	0.5-2	56-200	Good to injurious
III	Above 3000	Above 2000	Above 355	Above 480	Above 2	201-500	Unfit for irrigation

The results of the analyses from the Krishna Western Division indicated dissolved solids concentrations in groundwater and canal water samples of 1 364 ppm and 597 ppm, respectively. Blending these waters in a 1:1 ratio by volume results in a final TDS of 981 ppm, which is below 1 000 ppm threshold considered as the minimum quality for irrigation water. Similarly, in the Krishna Eastern Division, a 1:1 ratio of groundwater and canal water was found to produce a product water that is suitable for irrigation use. In contrast, in the Krishna Central Division, blending groundwater and surface water in ratios of up to 34:1 failed to result in a product water with a TDS concentration of less than 1 000 ppm. Hence, the utilization of groundwater is this Division was not considered further. Finally, in the Krishna Delta ayacut system, a blend of groundwater and surface water in a ratio of 28:72 was found to produce a product water suitable for irrigation use.

Operation and Maintenance

The operation and maintenance requirements of this technology includes the inspection and repair of pipelines, channels, and pumps, all of which make use of existing skills present within the agricultural community.

Level of Involvement

The Andhra Pradesh State Irrigation Development Corporation is the operator of the system. State Government agencies and financial institutions have provided the funds required to develop the necessary infrastructure to operate this technology.

Effectiveness of the Technology

The effectiveness of this technology in achieving the objective of conserving water resources is evident from the fact that 28% of the total water requirement of the Krishna Delta was met through the conjunctive use of surface and ground waters, conserving 750 million m³ of surface water which could be diverted to other uses. In subsequent phases of this project, this savings is expected to reach 1 065 million m³.

Advantages

The advantages of this technology include the conservation of large quantities of good quality surface water in a very cost effective manner. This technology may also have application in places where the good quality surface water is not abundant.

Disadvantages

Application of this technology requires additional infrastructure, including a tubewell pumping system, which incurs additional costs. It also requires additional monitoring of the operation of the system to ensure the quality of the blended water, as some of the crops are sensitive to salinity and changes in water quality. Also, soil quality may be sensitive to the quality of the water applied, requiring that the ratio of surface to ground water volumes should be closely monitored and properly maintained to prevent salination of the soils.

Further Development of the Technology

In view of the large demands on the waters of the Krishna River upstream of Nagarjuna Sagar Reservoir, it has become necessary to utilize the groundwater supplies available in the Krishna Delta area to the extent possible. Based upon water quality considerations arising from the analyses of groundwater, canal water, and soil samples of the ayacut, it is possible to conjunctively utilize groundwater and surface waters in the Delta in blends of up to 28:72. Such use would conserve up to 1 016 million m³ of surface water for other purposes.

Information Sources

Vishwanadh, G.K. and D.V. Reddy 1995. Conjunctive Use of Ground and Surface Water in Krishna Delta for Irrigation, Journal of Indian Institution of Engineers, Civil Engineering Division, 7'5:197-202.

5.8 Artificial groundwater recharge - India

Introduction

Technological developments in well construction and pumping methods have resulted in the large-scale exploitation of groundwater in India and elsewhere. In many parts of India, due to the vagaries of the monsoon, and, in the arid and semi-arid regions, to the lack or scarcity of surface water resources, dependance on groundwater has increased tremendously in recent years. Thus, given the potential for the available groundwater resources to be over-exploited in these areas, it is essential that proper storage and management of available groundwater resources be instituted.

Replenishment of groundwater by artificial recharge of aquifers in the arid and semi-arid regions of India is essential as the intensity of normal rainfalls is grossly inadequate to produce any moisture surplus under normal infiltration conditions. Although artificial groundwater recharge methods have been extensively used in the developed nations for several decades, their use in developing nations, like India, has occurred only during the last ten to twenty years. Techniques such as nalah bunding, constructing percolation tanks, trenching along slopes and around hills, etc., have been used for some time, but have typically lacked a scientific basis (e.g., a knowledge of the geological, hydrological and morphological features of the areas) for selecting the sites on which the recharge structures are located. For this reason, between 1980 to 1985, the Central Ground Water Board (CGWB) implemented a full-scale technical feasibility and economic viability study of various artificial recharge methods in the semi-arid and drought affected areas of Gujarat, Maharashtra, Tamil Nadu and Kerala. In Gujarat, detailed investigations were carried out (i) in the Central Mehsana area of North Gujarat where large-scale over-exploitation of groundwater has resulted in substantial declines in the water table during past three decades, and (ii) in the coastal areas of Saurashtra where overexploitation of groundwater has resulted in salt water intrusions into the aquifers. In Maharashtra, detailed studies of recharge of basaltic and alluvial aquifers using percolation tanks were carried out in the Sina and Man River basins. In Tamil Nadu and Kerala, similar studies were carried out in the Noyil Ponani and Vattamalai River basins, respectively.

Technical Description

The CGWB survey identified a number of techniques commonly used for artificial recharge. Some, such as the use of injection or connector wells, are largely experimental, while others, such as surface spreading methods, are actively used. The critical feature of the injection well technique is the selection of the aquifer to be recharged. The selection of sites for these recharge structures depends on the configuration of the deep (greater than 100 m depth), confined aquifers, the hydraulic gradient, and the location of the source of excess surface water. As a rule of thumb, it is always better to construct the structures close to water source to save on the cost of transportation of water to the recharge site and to minimize the potential lag time involved as a consequence of the slow rate of subsurface movement of groundwater. The actual designs of the injection wells and connector wells are not much different from those of the normal tubewells and depending upon the aquifer characteristics, slot sizes, casing sizes and gravel packing are to be selected. In contrast, groundwater recharge by spreading is best practised in shallow (40 m to 100 m), unconfined or leaky aquifers. Several methods are commonly used. Channel spreading involves changing the pattern of the surface flow in the river channel using "L"-shaped levees (sand bunds), slowing the rate of river flow and increasing the channel length to provide more time for infiltration. However, in areas where rivers are ephemeral and prone to flash flooding, the application of this technique is limited as the levees are destroyed during the flash floods. More successful is the use of spreading channels which use artificial, unlined canals to recharge the groundwater reservoirs. The spreading channels have side slopes of 1:1 and very gentle floor gradient slowing the downstream movement of water, allowing time for infiltration, and reducing erosive action of the water. These features make the structures relatively stable and limit the deposition of wind blown silt on sides of the canals. A variant of this technique is the use of contour trenching, which is better suited for use in hilly areas where surface runoff rates are very high. Planting of trees along contour bunds or trenches further helps to reduce surface runoff rates and soil loss due to erosion. A further variation of the surface spreading technique is the use of recharge ponds, percolation tanks, check dams, and subsurface dikes. These lentic waterbodies create a "mound" of groundwater within the aquifer immediately below the ponds, which extends up to between 100 m and 1 000 m from the recharge structure, depending upon availability of water for recharge. These are the cheapest modes of artificial recharge. However, the design of the recharge structure requires careful consideration to ensure the correct sizing of the pond both to provide sufficient recharge to meet abstraction demands and to adequately contain stormwater runoff. For an average village with population of up to 500 persons, a 0.5 ha pond, with little water loss due to overflow, is sufficient to provide enough recharge to service the potable water requirements of a tube well-based water supply system. Where there is insufficient stormwater runoff to fill the pond, water from the surrounding area should be diverted to the pond with minor trenches. In India, the subsurface dike is the most suitable structure for promoting groundwater recharge as it is safe from floods, needs no elaborate overflow devices, and is least susceptible to silting. In addition, subsurface structures do not require extensive areas of land for their implementation and, hence, have minimal ecological repercussions following their construction. Since the entire structure is underground, evaporative losses are also insignificant. Two subsurface dikes of 100 m length each, within 300 m upstream and downstream of the water supply well, can capture and infiltrate enough water to service the potable water requirements of a village of up to 500 persons (if only one structure is constructed, it should be downstream of the well point, as the groundwater mound created by the barrier will also act as a subsurface barrier and capture groundwater flows from upstream of the well). Some arrangement for subsurface outflow from the dike is often desirable to avoid waterlogging. Check dams are the least desirable form of this technology, and should generally be used only where the recharge requirement is very high or there is a need to control soil erosion. Check dams require a 30 cm to 60 cm wide concrete or brick masonry dike extending down to an impermeable basement stratum or compacted foundation. In general, the sites selected for construction of ponds, tanks, dams and dikes are normally those where manual excavation is possible. Such sites are typically those that (1) have undergone intense weathering, and, as a result, have a high fracture porosity, or (2) are in alluvial areas, which are best suited for infiltration.

In areas where rainfall is scanty and the drought frequency is high, infiltration of rain water is best accomplished by employing an integrated series of techniques, which, for example, can include damming the gullies of minor streams, constructing subsurface dikes and/or percolation tanks along their tributaries, contour bunding and trenching on slopes, placing farm ponds in the foot hills, and, wherever possible, installing check dams-cum-minor irrigation dams on the main stream courses. Terracing and afforestation of hillsides, which help to retain runoff and increase infiltration, may also form part of an integrated basin-scale water resources development plan.

In India, an important factor in the design of artificial recharge structures is the consideration of their stability during probable, high flow storms during years of above average rainfall and occasional flash floods. Such structures should also be designed in such a manner as to minimize the accumulation of silt and organic matter within the structure. For example, the infiltration capacity of ponds is reduced by up to 25% each year as a result of siltation, and, by the end of fifth year of operation, is reduced to about 10% of the total storage. Thus, 90% of stored water is lost to evaporation. Table 40 summarises the relative suitability of the various types of artificial recharge structures for a number of typical applications.

TABLE 40. Suitability of Artificial Recharge Structure for Common Water Resource Development Purposes.

Lithology	Topography	Type of Structure
Alluvial or hard rock to 40 m depth	Plain area or gently undulating area	Spreading pond, subsurface dike, minor irrigation tank, check dam, percolation tank, or unlined canal system
Hard rock down to 40 m depth	Valley slopes	Contour bunding or trenching
Hard rock	Plateau Regions	Recharge ponds
Alluvial or Hard rock with confined aquifer to 40 m depth	Plain area or gently undulating area	Injection well or connection well
Alluvial or Hard rock with confined aquifer to 40 m depth	Floodplain deposits	Injection well or connection well
Hard rock	Foot hill zones	Farm ponds or recharge trenches
Hard rock or alluvium	Forested areas	Subsurface dikes

Extent of Use

The techniques described above have been employed in the states of Maharashtra, Gujarat, Tamil Nadu and Kerala. In Maharashtra, studies were carried out on seven percolation tanks in the Sina and the Main River basins. The average recharge volume of these tanks was 50% of the capacity of the tank, provided the tank bottom was maintained by removing accumulated sediment and debris prior to the annual monsoon. Best results were obtained from systems located in areas of vesicular or fractured basalt. Nalah (stream) bunding, where the recharge structure was situated within the course of the nalah, was found to be most effective and economical as the surface area exposed to evaporation was, on average, 10% of that of an average-sized percolation tank. Within nalah bunds, the rate of infiltration varied from 50% to 70% of the capacity of the reservoir. Infiltration was aided by a connector well linking the phreatic, alluvial aquifer at 6 m depth with the deeper, confined basaltic aquifer at 63 m depth, allowing the free flow of water by gravity from phreatic aquifer to the confined aquifer at the rate of 0.19 million m3/year. The water level in the phreatic aquifer, which was saturated due to infiltration from the surface reservoir, was 3 m below ground level, and the piezometric level in confined aquifer was 30 m below ground level.

In Tamil Nadu and Kerala, studies were carried out on nine percolation tanks in the semi-arid regions of the Noyil Ponani and Vattamalai River basins. Rates of percolation were as high as 163 mm/day at the beginning of the rainy season, but diminished thereafter mainly due to the accumulation of silt in the bottoms of the tanks. Periodic desilting, therefore, was determined to be an essential element in the maintenance of these tanks. In contrast, subsurface dikes of 1 m to 4 m in height were found effective in augmenting groundwater resources, particularly in the hard rock areas underlain by fractured aquifers.

In Punjab, studies of artificial recharge using injection wells were carried out in the Ghaggar River basin, using canal water as the primary surface water source. The injection rate was initially 43.8 l/sec at an injection pressure of one atmosphere (atm). The pressure increased to 2 atm after 5 hours, and remained constant thereafter, although the recharge rate gradually diminished to 3.5 l/sec after few days. The natural, gravity-controlled recharge rate was 5.1 l/sec. Notwithstanding, over time, the reproducable recharge rate obtained using the pressure injection system was found to be about 10 times greater than the rate obtained using gravity flow. The increase in pressure during injection was due to clogging of the interstitial spaces within the aquifer, which can be minimized by careful control of the source water quality. Periodic cleaning of well was also required, whenever the pressure increased beyond 6 atm or showed a sudden rise. Further studies were conducted on induced recharge from the Ghaggar River using a well field, with individual wells spaced at 200 m intervals, within 100 m of the river bank. As with the injection wells, periodic removal of the clay film deposited in the floodplain above the natural recharge areas of the aquifer was required to improve recharge efficiency.

In Gujarat, studies of artificial recharge were carried out in two areas. In the Central Mehsan area of North Gujarat, artificial recharge was carried out using injection wells, connector wells, and infiltration channels and ponds. Surplus groundwater from the floodplain aquifers of the major rivers in Mehsana area and tail-end releases from the Dharoi Canal System were utilized as the water sources. In addition, the injection of water from the phreatic aquifers into the deeper, overexploited aquifers was investigated in the Central Mehsana area. In the coastal areas of Saurashtra, artificial recharge was carried out using injection wells and recharge basins. Stormwater runoff and tail-end releases from the canal system of the Hiran Irrigation Project were used as the water sources, and the studies included an evaluation of the effectiveness of the existing tidal regulators and check dams, designed to limit the extent of seawater intrusion. Of the methods studied in the Central Mehsana area, spreading methods, using techniques such as spreading channels, recharge pits and ponds, were found to be more economical than injection methods, although dual purpose connector wells were found to be more economical for recharging the deep aquifer. The dual purpose connector wells not only supplied water by gravity to the deep aquifer, but also abstracted water by periodic pumping, which reduced the extent of clogging of the wells. In contrast, the coastal Saurashtra area where the aquifers are highly porous and drain to the coastal zone, the rapid outflow of recharged water to the sea did not make artificial recharge a viable proposal.

However, the tidal regulators which created barriers of freshwater along the creeks and in coastal depressions effectively prevented seawater intrusion in these areas.

Also in Gujarat, studies of subsurface storage were carried out. In the Jamnagar District, naturally-occurring baslatic dikes were known to retain groundwater. However, it was also known that the surface soils in the District were not waterlogged. The studies indicated that, while the lower portion of the dike acted as a barrier to the passage of groundwater, the top few metres of the dike, composed of fractured basalt, allowed the passage of groundwater through the soil profile, preventing waterlogging in the aquifer area. This design feature was subsequently incorporated into the specifications of subsurface dikes.

Elsewhere in India, watershed management practices adopted in some states to minimize soil loss in erosion gullies also contribute to groundwater recharge. Check dams not only store surface water during portions of the year, but also encourage infiltration into the surfacial aquifers, providing a threefold benefit to communities (i.e., prevention of soil loss, provision of water for livestock watering and human use, and groundwater recharge). Such works have been implemented on an extensive scale in Gujarat, Maharashtra, Madhya Pradesh, and Rajasthan since 1960.

Operation and Maintenance

Periodic maintenance of artificial recharge structures is essential because infiltration capacity is rapidly reduced as a result of silting, chemical precipitation, and accumulation of organic matter. In the case of spreading structures, annual maintenance consists of scraping the infiltration surfaces to remove accumulated silt and organic matter. In the case of injection wells and connector wells, periodic maintenance of the system consists of pumping and/or flushing with a mildly acidic solution to remove encrusting chemical precipitates and bacterial growths on the well tube slots. By converting the injection or connector wells into dual purpose wells, the interval between periodic cleanings can be extended, but, in the case of spreading structures except for subsurface dikes constructed with an overflow or outlet, annual desilting is a must. Unfortunately, because the structures are installed as a drought relief measure, the periodic maintenance is often neglected until a subsequent drought, at which time the structures must be restored (the 5 to 7 year frequency of droughts, however, means that some maintenance does take place). Structural maintenance is normally carried out by several agencies and individuals. Maintenance of minor irrigation tanks is normally carried out by the state irrigation department, maintenance of contour bunds and trenches (along with related afforestation activities) by the state forestry department, and maintenance of farm ponds and related structures by the cultivators.

Level of Involvement

The recharge schemes and related land development activities primarily depend on the cooperation of the community, and, hence, should be managed at the local level. Hence, from the basin management perspective, the division of a basin into many micro-catchments is an essential recognition of this community role. The achievements attained depend on public participation and active contribution to the projects, with any shortage of funds being overcome by the willingness of individuals to come forward, take over the management of the system, and offer Shramadan. As the areal extent of a typical village averages 1 000 to 1 500 ha, a micro-catchment of a similar areal extent is ideal. In addition to the community level participation, many basin development projects, being multi-disciplinary schemes, involve the state irrigation and forestry departments, and the local cultivators.

Costs

The costs of recharge schemes, in general, depend upon the degree of treatment of the source water, the distance over which source water must be transported, and stability of recharge structure and resistance to siltation and/or clogging. In these studies, simple methodologies were developed to minimize costs by more steeply sloping the sides of the spreading structures to reduce the rate of silt accumulation, by packing gravel into recharge pits to avoid the collapse of the sides due to wave action of the stored water, by desilting the source water using gravel beds within the infiltration channels or in sedimentation basins, and by ensuring the placement of a proper gravel pack around a phreatic zone injection well to allow silt free water to enter deeper aquifers. In general, the costs of construction and costs of operation of the recharge structures, except in the cases of injection wells in alluvial areas and tidal regulators in coastal areas, are reasonable, although, given the average requirement for irrigation water of 5 000 m3/ha, the comparative cost of recharged water, of $5 to $15 per hectare per crop, is significantly higher than alternative sources. In contrast, the cost of using recharged groundwater for domestic water supply purposes, of $0.05 to $0.15 per person per year, is reasonable, especially in areas where there is a shortage of water. The initial investment and operating costs are many times less than those required for supplying potable water using tankers, for example, and, when the recharge systems are constructed by state governments as relief works, thereby eliminating the labour costs, the capital cost to the beneficiary community is further reduced. Combining technologies can also result in cost savings. For example, in Maharashtra, the capital cost of an hybrid, connector well-tank scheme was about $900 (the cost of the borehole) compared to the cost of a comparable percolation tank system needed to achieve a similar degree recharge (estimated to be about $120 000). Table 41 summarizes the costs of various artificial recharge methods.

TABLE 41. Economics of Various Artificial Recharge Methods

Artificial Recharge Structure Type	Capital Cost/1 000 m3 of Recharge Structure	Operational Cost/1 000 m3/year
Injection well (Alluvial area)	$55	$21
Injection well (Hard rock)	$2	$5
Spreading channel (Alluvial area)	$8	$20
Recharge pit (Alluvial area)	$515	$2
Recharge pond or percolation pond (Alluvial area)	$1	$1
Percolation tank (Hard rock area)	$5	$1
Vasant Bandhava of Check dam	$1	$1
Tidal regulator	$56	$15

Effectiveness of the Technology

The various techniques used for the artificial recharge of groundwater aquifers proved to be effective in storing water for human use in all of the states of India, with the possible exception of the coastal zone, where the extreme porosity of the aquifer and its connection to the sea resulted in less water being available for harvest than was injected. In general, recharge was effective in minimizing water loss due to evaporation compared with similar surface storage systems.

Advantages

Among the spreading methods, subsurface dikes are most desirable because they need little maintenance, are safe from natural catastrophes, minimize evaporative losses, and avoid many of the environmental problems arising from surface storage. There is also no loss of agricultural lands or forests by inundation as would occur behind a surface storage structure. In cases where channels are used for groundwater recharge, multiple benefits may be achieved by combining irrigation and infiltration channels in a number of river basins.

Disadvantages

One of the main disadvantages of recharge structures, such as ponds, trenches, and percolation tanks, is that they require regular maintenance to avoid siltation and subsequent clogging of the recharge basin. There is also the possibility of waterlogging in some areas due increased groundwater levels. Further, injection and connector wells are costly schemes requiring high order of quality control of the infiltration source water.

Further Development of the Technology

The use of this technology requires a knowledge of the geological conditions; rock formations with moderate permeability are most desirable as low permeabilities limit storage volumes and high permeabilities do not allow adequate retention of the recharged water. The relative cost of recharged water also limits its application to augmenting domestic water supplies as it is not economically viable for irrigation purposes in India. Groundwater recharge is often best accomplished as a byproduct of an integrated water resources development scheme; e.g., increasing groundwater recharge by way of reservoir and canal seepage, injection and infiltration of recycled irrigation water, enhanced infiltration of rainfall as a result of levelling fields for irrigation purposes, and basin development schemes involving the construction of check dams and minor irrigation dams. Proper systems of maintenance of structures through the participation of government agencies, cultivators and communities are also required.

Information Sources

National Drinking Water Mission and Department of Rural Development 1989. Rain Water Harvesting, Government of India, New Dehli.

5.9 Integrated water conservation - Bhilai steel plant, India

Introduction

Bhilai and its adjoining areas in the Durg and Raipur Districts of Madhya Pradesh State in India experience severe water shortages. For example, in 1988, the Bhilai area, in the vicinity of the steel plant, received only 636 mm of rainfall, compared to the long-term average rainfall of 1 300 mm. As a result, the reservoirs of the Mahanadi Reservoir Project and Tandula Complex, which supply water to Raipur and Durg Towns and village nistari tanks for irrigation, industries and drinking purposes, were reduced in volume to 22.3% of their full supply capacity, or to a live storage of 391 million m³. In comparison, the annual consumption of water at the Bhilai Steel Plant during the previous financial year (1987-88) was 297 million m³. Given the available storage in the reservoirs in 1988, it became essential to reduce the consumption of water until the next monsoon.

Technical Description

As a first step in preparing a comprehensive strategy for managing water resources at the Bhilai Steel Plant, an inventory was prepared identifying areas in the plant where reuse and recycling could be achieved, and an audit conducted of water uses to identify areas in the plant where water consumption could be reduced. In terms of these studies, a number of rain water outlets in the plant, carrying substantial quantities of effluent, which had a potential to be recycled, into the Marida-I Reservoir, were intercepted and diverted to various pump houses so that their recycling was possible. Similarly, the ash slurry from Power Plants-1 and -II was conveyed to an Ash Pond (No. 2) for settlement of solids and recycling of the clarified water. Approximately 1 000 m³/hr was conserved in this manner and returned into the pressure mains for reuse in the Rolling Mills area of the plant. Likewise, the Horizontal Secondary Settling Tanks (HSST) and the overflow channels were found to be poorly maintained, resulting in substantial spillages, which were eliminated by cleaning the return channels so as to ensure that the settled water is contained within the rain water outlet system for later recovery. Additional reenforced concrete pipes were laid to interconnect the rain water outlets to avoid any effluent spills. In addition to the effluent recycling from selected outlets, seepage from the Marida-I Reservoir was also intercepted and routed via the pump house into the recycling system, and water discharges from the Plate Mill, previously routed to a subsoil soakaway, were diverted as make up water to the circulating water pump house at the Plate Mill and to the CAS-III Pump House. The water supply to the townships was also checked and the supply hours were reduced to an half hour in the morning and an half hour in the evening. Such a practice did not cause any serious inconvenience in the townships but helped conserve 1 000 m³/hr of water.

In addition to the recycling schemes, other actions designed to reduce water consumption were also taken, including stopping the water supply to any Mill that was taken out of production for whatever reason; stopping overflows from the suction pumps in the pump houses and cooling towers; improving maintenance of, and stopping leaks in, industrial water supply lines; isolating damaged lines to stop wastage; minimizing the use of water by the Horticulture Department for gardening; and, using posters and public announcements to raise awareness of the need for water conservation amongst staff and township residents.

Extent of Use

All the major schemes were completed within five months. There was no major resistance to the water conservation measures from the staff of the plant or from the residents of the townships towards water conservation efforts.

Operation and Maintenance

The major operation and maintenance aspects considered were "good housekeeping" at the facility, constant monitoring and preventive maintenance to minimize losses through leakages, improving operations and supervision of the pumping stations, and monitoring of concentrations of potential pollutants in the effluents and the quality of the Maroda-I Reservoir.

Level of Involvement

The public sector was completely responsible for the implementation of the recycling and conservation programme at the steel plant. However, community involvement was important in conserving water in the residential townships.

Costs

The capital costs incurred for water conservation at this facility included procurement and installation costs associated with the upgrading of pumping facilities prior to implementation of the recycling programme. In addition, costs were incurred for pump operation, for cleaning and maintenance of the effluent and water pipes, and for descaling and the removal of sludge from pipes. The actual cost figures are not available.

Effectiveness of the Technology

Due to the implementation of the water conservation strategies, the industrial make up water consumption was reduced from 16 740 m³/hr to 3 000 m³/hr at the additional cost of pumps, interconnecting pipes, cleaning and pump operation. Table 35 shows that the industrial water consumption per tonne of steel produced has been reduced from 52.2 m³ to 9.3 m³, a substantial reduction in water use.

Advantages

The advantages of implementing water conservation measures include a lower water supply costdue to a five- to tenfold decrease in water consumption, the ability to continue operations despite reduced water resource availability, the conservation of 14 000 m³/hr of water, an heightened awareness of the need for water conservation amongst the plant staff as well as the residents of the township, and a priority being given to water conservation by the senior management.

Disadvantages

Amongst the disadvantages were an increase in hardness, and suspended and dissolved solids and chloride concentrations in the plant effluent which required increased monitoring to meet pollution control and process water quality standards and an increased frequency of backwashing ion exchange columns, and which led to a marginally greater degree of impairment of water quality (particularly, increased turbidity) in the Maroda-I Reservoir. To mitigate the latter impact, sodium metaphosphate has been added to the Maroda-I Reservoir to inhibit turbidity and discourage scaling in the pipelines by forming a film within the pipes. A further disadvantage of this technology was that, as the water conservation measures use pumping as the principal means of circulating the recycled waters, the water conservation system incurred higher energy costs.

TABLE 42. Reduction in Water Consumption at the Bhilai Steel Plant.

Period	Total water consumption m3/hr	% Savings	Industrial water consumption per tonne of crude steel
April to August 1988 (average)	25550	-	52.2
September 1988	21245	16.8	48.3
October 1988	19852	22.3	36.9
November 1988	13863	45.7	18.8
December 1988	11448	55.2	12.2
January 1989	9165	64.1	5.2
February 1989	12278	51.9	10.3
March 1989	10771	57.8	4.8
April 1989	12777	50.0	9.5
May 1989	13728	46.3	12.3
June 1989	11453	55.2	10.3

Further Development of the Technology

Water conservation efforts within public sector enterprises such as Bhilai Steel clearly demonstrate that significant opportunities exist for the conservation of large quantities of water, in this case 14000 m³/hr, using relatively simple methods such as better maintenance, reuse of process water, and recycling. However, it is also important to concomitantly explore water reduction, through technological modifications, for example, in addition to focussing on reuse. Such a strategy, in the longer term, could reduce the relatively high operating costs of the recycling-based scheme to a great extent.

Information Sources

Tambe, G.N. 1990. Journal of Indian Water Works Association, Jan-March, pp. 33-36.

5.10 Drip irrigation - India

Introduction

Drip irrigation is of recent origin, and, in India, is being used on a limited scale in Tamil Nadu, Karnataka, Kerala and Maharashtra States, mainly for coconut, coffee, grape and vegetable production. Drip irrigation systems (DIS) are extremely effective in arid and drought prone areas where water is scarce, and have been used experimentally in India for over 15 years: in the States of Tamil Nadu, Karnataka, Maharashtra, and Andhra Pradesh, progressive farmers started using this method of irrigation in the late-1970s without the benefit of any subsidies or support from central or state governments. However, as a result of subsequent, sustained efforts by the state and central governments, agricultural universities, and private sector manufacturers, use of drip irrigation systems spread through the drought prone areas of southern and western India. The use of DIS, however, is primarily to irrigate high value, horticultural crops. In states like Maharashtra, Karnataka, and Tamil Nadu, DIS are sometimes used for irrigation of vegetable and other commercial crops. The sharp rise in the area under DIS irrigation between 1988 and 1989 is due, in large part, to the significant increase in the use of these systems in the Maharashtra State.

Technical Description

Drip irrigation systems deliver water and agrochemicals (e.g., fertilizers and pesticides) directly to the root zones of the irrigated plants at a rate best suited to meet the needs of the plants being irrigated. Thus, this system makes efficient use of water, especially when compared to conventional methods of irrigation such as furrow, border, basin and sprinkler irrigation systems, which, under arid and drought conditions, suffer from an high rate of water loss and have a low degree of water use efficiency.

Extent of Use

Drip irrigation systems are used throughout the arid parts of India, especially in Maharashtra, Haryana, Meghalaya, and Rajasthan. At Rahuri, in Maharashtra State, the use of drip irrigation of pomegranates, grown in gravely soils, resulted in a savings of about 44 cm of irrigation water, or 44%, over the conventional check basin irrigation systems previously used, as shown in Table 43. The water use efficiency was also much higher using the drip method of irrigation, especially when combined with the use of mulch, which effected a further savings of irrigation water of 14% when compared to un-mulched plots. Similarly, at Dapoli in the Konkan Region of Maharashtra State, where, despite an annual rainfall of about 4 000 mm, the period between December and May is often a time of severe drought, drip irrigation systems were used to irrigate mango and cashew crops. The soils of the Region are highly porous laterites, which are poorly suited to supporting conventional, pond-fed irrigated agriculture, particularly of row crops. Nevertheless, the Region has an high potential for the production of crops like mangoes and cashews. However, to establish mango or cashew orchards, it is essential to provide adequate water during the first two to three years after transplanting the seedlings, which, during the dry season, can only be supplied through irrigation, In the mango orchards, an indigenously designed drip irrigation system was installed using a common, earthen pitcher placed at an higher elevation than the plants and a siphon to direct the water to the trees by means of two to three drippers per stem. This system helped to quickly establish the orchards, with a considerable savings in irrigation water compared to prevalent practice of hand watering the trees. As shown in Table 44, there was also substantial improvement in plant growth, as measured by height, girth, and plant spread, using drip irrigation compared to the conventional hand watering method. The application of about 45 I/plant/week of water appeared optimal.

In Haryana and Rajasthan States, drip irrigation of potatoes grown in loamy sand soils at Jobner, of onions, sugar beets, and potatoes grown in sandy loam soils at Hissar, and of bhindi and sugarcane grown in clay soils at Rahuri (clay soil) resulted in improved crop yields and a savings in irrigation water of between 18% and 40%, except at Jobner where few differences were apparent between irrigation methods used. Nevertheless, there was substantial improvement in the water use efficiency of the crops at all three centres.

TABLE 43. Yield of Pomegranates Using Different Irrigation Methods on Gravel Soils.

Treatments		Yield (q/ha)	Depth of Irrigation (cm)	Water Use Efficiency (kg/ha/cm)
I. Check basin
	a) Without mulch	78.6	108	72.7
	b) With mulch	74.8	92	81.3
	Mean	76.7	100	77.0
II. Drip Method
	a) Without mulch	68.4	60	113.5
	b) With mulch	70.6	52	175.2
	Mean	69.5	56	244.3

TABLE 44. Effect of Drip Irrigation on the Growth of Mango Plants.

Quantity of water applied/plant/week (l)	Percentage increase in
	Height	Girth of Scion	East-West Spread	North-South Spread
Using Drip Irrigation
15	20.1	31.6	31.1	28.4
30	25.5	33.4	34.8	31.4
45	25.2	38.6	34.4	32.0
60	28.6	37.8	38.8	36.7
Using Hand Watering
60	17.5	29.8	25.1	22.3

Similarly, at Hissar, the use of drip irrigation systems supplied with irrigation water from a poor quality source (having an electrical conductivity of 6.5 mmhos/cm) resulted in only a 12% decrease in the yield of radishes using drip irrigation compared to surface irrigation methods using the same poor quality source water, which resulted in a decrease in yield of 39.5%. Even under these conditions, water use efficiency increased almost threefold with drip irrigation compared to conventional surface irrigation techniques as shown in Table 46. A well-managed drip irrigation system supports the use of poor quality of water because the irrigation water is applied continuously, ensuring that the root zone does not dry out and that the salts move away from the root zone. Thus, the accumulated salt is leached to the edge of the wetted soil mass where it does not interfere with the growth of the plants. Also, since a much smaller quantity of water is applied to the soil, the total salt load applied is likewise lower.

TABLE 45. Yield of Radishes Using Drip Irrigation.

Irrigation method	Canal water		Poor quality water
	Root yield (q)	Water Use Efficiency (q/ha/cm)	Root yield (q)	Water Use Efficiency (q/ha/cm)
Surface	163.5	13.7	98.9	8.7
Drip	268.1	29.8	236.0	26.2

TABLE 46. Yield of Brinjals Using a Salt Water Drip Irrigation System.

Salinity (ppm)	Conductivity (mmhos/cm)	Salinity (at 10 cm depth and 10 cm away from root zone)	Salinity (at 20 cm depth and 20 cm away from root zone)	Yield (kg/ha)
850	660	21	361	5250
2500	1680	19	110	5 127
7500	3290	27	129	4738
10000	4500	558	180	4122

In Meghalaya, some of the tribal farmers use a drip irrigation system constructed of bamboo to irrigate betel, pepper and arecanut crops. The system is indigenously designed using locally available materials. The hillsides on which this system is used have a rock and soil mixture with poor water holding and retention capacities that require frequent applications of irrigation water. Using this system, water from natural stream is diverted at a point of higher elevation than the plot to be irrigated, and is conveyed by gravity through bamboo channels, supported on ground surface by wooden or bamboo supports, to the point of application. The discharge at the head channel varies from 15 to 20l/min and is reduced to between 10 and 30 drops/min at the point of irrigation water application. The elevation of the head channel may be up to a few metres higher than the irrigated field elevation, whereas the elevation of the last channel may be less than 10 cm to 15 cm above the ground surface.

At Jobner in Rajasthan, earthen pitchers and porous cups have been used successfully for irrigating vegetable crops, such as crops of cabbage, cauliflower, and knolkhol. The technique uses earthen cups of 500 ml capacity embedded in the soil at the site of the seedlings. The cups are filled to the brim with water at intervals of 4 to 5 days. Because of their underground situation, the cups experience little water loss due deep percolation and/or evaporation. At Karnal, using a similar technology, earthen pitchers of about 15 l capacity have been used for irrigating cucumbers and radishes. This technology provides irrigation water to the crops at a rate of less than 2 cm/ha. These innovative technologies permit the cultivation of vegetables and cash crops in areas where it is not practical or possible to grow crops using conventional surface irrigation methods.

Operation and Maintenance

The principle operation and maintenance requirements associated with the implementation of this technology include the need for regular cleaning of the system and careful monitoring of the quality of the source water, as the drip irrigation systems are very sensitive to the clogging of the drippers. The systems also require a relatively high degree of skill to design, install and operate, and are susceptible to theft, damage and disruption by rodents that destroy the drip pipes and drippers.

Level of Involvement

The use of this technology requires skilled personnel. Because of the relatively high capital cost of the piping systems necessary to implement this technology, the initial funding for the project may require some level of government involvement. Regular operation and maintenance of the system is the responsibility of the individual operator.

Costs

The capital costs involved in the establishment of a drip irrigation system are high compared to the costs of establishing conventional irrigation systems. However, the labour requirements and operational costs are low. The net result is that the benefit-cost ratio for DIS is very favourable compared to conventional systems since the payback period for investment very short. In the case of the orchard crops in Maharashtra, the cost of DIS ranged from $450/ha to $1 150/ha in 1990. Elsewhere, the cost of using drip irrigation systems for sugarcane irrigation averaged $715/ha, for banana irrigation $1 150/ha, and for cotcrus-fruit irrigation $575/ha, with the payback periods ranging from 2 months for banana crops, 12 months for cotcrus-fruit crops, and 18 months for surgarcane crops. Comparative benefit-cost ratios for various crops ranged from 1.64 for groundnuts (peanuts), to 4.84 for pomegranates, to 5.15 for tomatoes, to 8.58 for grapes, to 15.0 for mosambi. These ratios compare to benefit-cost ratios of 1.80, 2.20, 3.96, 6.38, and 9.81, respectively, using conventional irrigation systems.

Effectiveness of the Technology

In almost all of the cases reported, excepting the Jobner case, there was an improvement in crop yields and savings in water use of between 18% and 40%. Consequently, there was a substantial improvement in the water use efficiency that ranged up to three times that of water use efficiencies achieved using conventional surface irrigation methods, even with the use of poor quality irrigation water. Because of the directed delivery of irrigation water, it is possible to utilize poor quality irrigation water using the drip irrigation system. The performance of this technology is summarized in Tables 40 and 41. The data presented in Table 40 are based upon water savings and increased yields achieved in Maharashtra State using drip irrigation systems. In addition to the improved yields and water savings, for crops such as sugarcane there is a savings in labour costs that equals the savings in water.

Advantages

The advantages of drip irrigation systems include an high efficiency of water use and greater crop yields compared to other irrigation methods. In addition, crops irrigated using drip irrigation systems generally require less tillage and are of better quality. DIS also contribute to improved plant protection and reduced occurrences of plant diseases and greater efficiencies in the use of fertilizers, because water containing the agrochemicals is applied directly to the plant roots in the quantities necessary for optimal plant production. For a similar reason, DIS can also make use of lower quality water, and results in no return flows, tail water losses or increased soil erosion. Because water is applied in optimal quantities, plants generally have a shorter growing season and produce fruit earlier, with less weed growth and pest damage than conventionally irrigated crops. The lower labour requirements result in relatively low operational costs, with savings in labour of up to 90% of the costs associated with conventional systems, in part, because mechanical operations can be carried out simultaneously with the application of irrigation water. DIS can be used in hilly terrain and on lands with problem soils, and results in improved infiltration in soils with low conductivity. Drip irrigation systems are low pressure systems, which can be adapted for use in greenhouses, and with automated control systems.

Disadvantages

Drip irrigations systems have a sensitivity to the clogging of the drippers, which may require pretreatment of turbid source waters, and, if not properly installed, can cause moisture distribution problems. The systems are also susceptible to rodent damage. The systems have an high cost compared to conventional irrigation methods, and require higher levels of skill for design, installation, and operation, which make them liable to damage or theft.

TABLE 47. Water Savings and Increased Yields Achieved Using Drip Irrigation.

Crop	Water used by drip irrigation systems (mm/ha)	Water used by conventional irrigation systems (mm/ha)	% Saving of water	Yield using drip irrigation system (q/ha)	Yield using conventional irrigation systems (q/ha)	% increase in yield
Sugarcane	-	-	50	100000 tonnes	-	35
Bananas	-	-	50	29000 tonnes	-	50
Cotcrus-Fruit	-	-	50	80% harvest	10% harvest	50
Grapes	278	532	65-70	325 tonnes	264 tonnes	30
Pomegranates (plants spaced at 12-foot intervals)	785	1440	50-55	109 000	75000	30
Guavas	-	-	55-60	-	-	25
Caster Apples	-	-	50-55	-	-	20
Mosambi	640	1 660	60	150000	100000	50
Groundnuts (Peanuts)	580	900	35	3200	2675	20
Tomatoes	222	324	30	48000	32000	50

TABLE 48. Effect of Irrigation Method on Crop Yield and Water Savings.

Soils/Crops	Method of Irrigation	Crop yield (q/ha)	Depth of Irrigation	Water Use Efficiency (kg/ha/cm)	% Savings of water
Jobner (Loamy sand)
Potatoes	Surface	141.0	240.0	58.7	-
	Drip	141.0	173.0	81.5	27.9
Hissar (Sandy Loam)
Onions	Surface	93.0	620.0	15.0	-
	Drip	112.0	466.0	24.0	24.8
Sugar beets	Surface	418.4	492.0	85.0	-
	Drip	489.9	401.0	122.0	18.4
Potatoes	Surface	235.7	203.0	116.0	-
	Drip	344.2	152.0	227.0	25.1
Rahuri (Clay)
Bhindi (Pusa-Sawni)	Furrow	157.7	62.7	25.2	-
	Drip	177.2	32.4	54.6	39.6
Sugarcane (Co7219)	Furrow	1 221.0	231.0	528.0	-
	Drip	1 464.0	162.0	902.0	29.5

Further Development of the Technology

This is a proven technology suitable for use with high value crops. Several crops which can be irrigated using drip irrigation systems include sugarcane, groundnuts or peanuts, coconuts, cotton, coffee, grapes, potatoes, and all fruit crops, spaced vegetable crops, and flowers.

Information Sources

R.S. Saksena, Consultant Planning Commission and Chief Engineer (MI, Retd.), Ministry of Water Resources, Government of India, New Delhi.

Annex 1 - Additional references

Centre for Water Resources 1993. Biennial Report of 1991 and 1992: Alternative Approaches to Tank Rehabilitation and Management - An Experiment, Anna University, Madras.

Chakravarty, R.B. 1985. Necessity and Considerations for Conservation of Water, Journal of Institution of Engineers, Civil Engineering Division, 66:18-20.

Chandra, S. 1985. Recent Trends of Water Conservation in Drought Prone Areas, Journal of Institution of Engineers, Civil Engineering Division, 66:1-11.

Chaturvedi, A.C. 1985. Water Use and Reuse, Journal of Institution of Engineers, Civil Engineering Division, 66:42-45.

Deb, S.M. 1985. Utilizing otherwise Non-Utilizable Water Resources - A Thought and a Case Study, Journal of Institution of Engineers, Civil Engineering Division, 66:38-41.

Dhruva, V.V. 1985. Soil and Water Conservation in India - Problems and Prospects, Journal of Institution of Engineers, Civil Engineering Division, 66:30-37.

Gould, J.E. 1991. Rainwater Catchment Systems for Household Water Supply, Environmental Sanitation Reviews, No.32.

Ministry of Housing and Physical Planning and US Peace Corps-Nepal 1989. Rainwater Catchment Tank Construction Technical Manual, His Majesty's Government of Nepal, Kathmandu.

Mistry, J.F. and M.U. Purohit 1985. Attempts for Greater Conservation and Better Utilization of Water Resources in Gujarat, Journal of Institution of Engineers, Civil Engineering Division, 66:12-17.

Murti, N.G.K. 1985. Conservation of Water Resources and Recycling in India, Journal of Institution of Engineers, Civil Engineering Division, 66:26-29.

Prasad, T. 1985. Water Resource Planning - A Primary Step for Conservation of Water, Journal of Institution of Engineers, Civil Engineering Division, 66:21 -25.

Pundarikanthan, N.V. and L. Jayasekhar 1995. Proceedings of the National Workshop on Traditional Water Management for Tanks and Ponds, Centre for Water Resources and Ocean Management, Anna University, Madras.

Shankari, U. and E. Shah 1993. Water Management Traditions in India, PPST Foundation, Madras.

Shrestha, S.H. 1987. Economic and Human Geography of Nepal.

Sud, S.C. and M. Sivdas 1994. Water Resources Development in India - An Overview, Journal of Indian Water Works Association, July-September, pp 135-139.

Verma, H.N. and K.N. Tiwari 1995. Current Status and Prospectus of Rain Water Harvesting, INCOH Secretariat, National Institute of Hydrology, Roorkee, India.

Annex 2 - Table of conversion factors for metric and U.S. customary units

This water quantity equivalents and conversion factor lists is for those interested in converting units. The right-hand column includes units expressed in two systems - US Customary and International System (metric). Units, which are written in abbreviated form below, are spelled out in parentheses the first time they appear. To convert from the unit in the left-hand column to that in the right, multiply by the number in the right-hand column. Most of the quantities listed were rounded to five significant figures. However, for many purposes, the first two or three significant figures are adequate for determining many water-quantity relations, such as general comparisons of water availability with water use or calculations in which the accuracy of the original data itself does not justify more than three significant figures. Quantities shown in italics are exact equivalents - no rounding was necessary. Regarding length of time, each calendar year is assumed (for this list) to consist of 365 days.

US Customary		US Customary or Metric
Length
1 in (inch)	=	25.4 mm (millimetres)
1 ft (foot)	=	0.3048 m (metre)
1 mi (mile, statute)	=	5280. ft
	=	1,609.344 m
	=	1.609344 km (kilometres)
Area
1 ft2 (square foot)		0.09290304 m2 (square metre)
1 acre	=	43,560. ft2
	=	0.0015625 mi2
	=	0.40469 ha (hectare)
1 mi2	=	640. acres
	=	259.00 ha
	=	2.5900 km2 (square kilometres)
Volume or Capacity (liquid measure)
1 qt (quart, US)	=	0.94635 l(litre)
1 gal (gallon, US)	=	231. in3 (cubic inches)
	=	0.13368 ft3 (cubic foot)
	=	3.78541
	=	0.0037854 m3 (cubic metre)
1 Mgal (million gallon)	=	0.13368 Mft3 (million cubic feet)
1 Mgal	=	3.0689 acre-ft (acre-feet)
	=	3,785.4m3
1ft3	=	1,728. in3
	=	7.4805 gal
	=	28.317 1
	=	0.028317 m3
1 Mft3	=	28,317. M3
1 acre-ft (volume of water, 1 ft deep, covering an area of 1 acre)	=	43.560.ft3
	=	0.32585 Mgal
	=	1,233.5 m3
1 mi3 (cubic mile)	=	1,101.1 billion gal
	=	147.20 billion ft3
	=	3.3792 million acre-ft
	=	4.1682 km3 (cubic kilometres)
Speed (or, when used in a vector sense, velocity)
1 ft/s (foot per second)	=	0.3048 m/s (metre per second)
	=	0.68182 mi/hour (mile per hour)
1 mi/hr	=	1.4667 ft/s
	=	0.44704 m/s
Volume per Unit of Time (discharge, water supply, water use, and so forth)
1 gpm (gallon per minute)	=	0.00144 mgd (million gallons per day)
	=	0.0022280 ft3/s (cubic foot per second)
	=	0.0044192 acre-ft/d (acre-foot per day)
	=	3.7854 l/min (litres per minute)
	=	0.063090 l/s (litres per second)
1 mgd	=	694.44 gal/min
	=	1.5472 ft3/s
	=	3.0689 acre-ft/d
	=	1,120.0 acre-ft/d (acre-feet per year)
	=	0.043813 m3/s (cubic metre per second)
	=	3,785.4 m3/d (cubic metres per day)
1 billion gal/yr (billion gallons per year)	=	0.0013817 km3/yr (cubic kilometre per year)
1 ft3/s	=	2.7397 mgd
	=	448.83 gal/min
	=	0.64632 mgd
	=	1.9835 acre-ft/d
	=	723.97 acre-ft/yr
	=	28.317 l/s
	=	0.028317 m3/d
	=	2,446.6 m3/d
	=	0.00089300 km3/yr
1 acre-ft/yr	=	892.74 gal/d (gallons per day)
	=	0.61996 gal/min
	=	0.0013813ft3/s
	=	3.3794 m3/d
1 acre-ft/d	=	0.50417 ft3/s
Volume, Discharge or use per Unit of Area
1 in of rain or runoff	=	17.379 Mgal/mi2
	=	27,154. gal/acre (gallons per acre)
	=	25,400. m3/km2 (cubic metres per square kilometre)
1 in/yr	=	0.047613 (Mgal/d)/mi2
	=	0.073668 (ft/s)/mi2
1 (Mgal/d)/mi2	=	21.003 in/yr (inches-of rain or runoff - per year)
1 (ft3/s)/mi2	=	13.574 in/yr
	=	0.010933 (m3/km2 (cubic metre per second per square kilometre)
Mass (pure water in dry air)
1 gal at 15° Celsius (59° Fahrenheit)	=	8.3290 lb (pounds avoirdupois)
1 gal at 4° Celsius (39.2° Fahrenheit)	=	8.3359 lb
1 lb	=	0.45359 kg (kilogram)
1 ton, short (2,000 lb)	=	0.90718 Mg (megagram) or ton, metric

Prepared by John -C. Krammer, US Geological Survey (National Water Summary 1990-1991)

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