Technological Group

Technology

Sector of Use

Countries of Use (as presented at the Workshops)

Agriculture: Irrigation and/or Livestock

Domestic Water Supply

Industrial and/or Mining

FRESHWATER AUGMENTATION

Rainwater harvesting

· roof catchments

x

x

Argentina, Barbados, Brazil, British Virgin Islands, Costa Rica, Dominican Republic, El Salvador, Guatemala, Haiti, Honduras, Jamaica, Montserrat, Netherlands Antilles, Paraguay, Saint Lucia, Suriname, Turks and Caicos, US Virgin Islands.

· in situ

x

Argentina, Brazil, Paraguay.

Fog harvesting

x

x

x

Chile, Ecuador, Mexico, Peru.

Runoff collection

· paved and unpaved roads

x

Argentina, Brazil, Venezuela.

· surface structures

x

x

x

Argentina, Aruba, Brazil, Chile, Costa Rica, Dominican Republic, Ecuador, Panama, Saint Lucia, Suriname, Venezuela.

· underground structures

x

Brazil.

Flood diversion

x

Argentina, Brazil, Venezuela.

Water conveyance

· marine vessels

x

Antigua, Bahamas, Barbuda.

· pipelines, rural aqueducts, water tankers

x

x

x

Costa Rica, Dominican Republic, Ecuador, Jamaica, Panama, Saint Lucia.

Artificial recharge of aquifers

· infiltration barriers and canals, water traps, cutoff waters, surface runoff drainage wells, septic tanks, effluent disposal wells, and diversion of excess flow from irrigation canals into sinkholes.

x

x

Argentina, Brazil, Paraguay, Barbados, Jamaica, Netherlands Antilles.

Groundwater pumping using non-conventional energy sources

· hydraulic pumps, hydraulic ram, rope pumps, hand pumps, windmill driven pumps, and photovoltaic pumps.

x

x

Argentina, Bolivia, El Salvador, Haiti, Honduras, Panama, Peru.

WATER QUALITY IMPROVEMENT

Desalination

· reverse osmosis

x

x

x

Antigua and Barbuda, Argentina, Bahamas, Brazil, British Virgin Islands, Chile, Turks and Caicos, U.S. Virgin Islands.

· distillation

x

x

Antigua and Barbuda, Aruba, Chile, Netherlands Antilles, U.S. Virgin Islands.

Clarification

· plants and plant material

x

Bolivia, El Salvador, Guatemala, Peru.

Disinfection

· boiling

x

Dominican Republic, Ecuador.

· chlorination

x

Guatemala, Montserrat.

Filtration

· residential filters, slow sand filters, rapid sand filters, dual and multimedia filters

x

Dominican Republic, Ecuador, El Salvador, Guatemala, Mexico.

WASTEWATER TREATMENT & REUSE

Wastewater Treatment

· oxidation ponds, stabilization lagoons, septic tanks, anaerobic filtration, sludge layer systems, hydroponic cultivation/root zone treatment, activated sludge in vertical reactors

x

Aruba, Brazil, Colombia, Dominican Republic, Mexico, Netherlands Antilles.

Wastewater Reuse

x

x

Argentina, Barbados, Brazil, Guatemala, Jamaica.

WATER CONSERVATION

Water Conservation

· raised beds and waru-waru cultivation

x

Peru

· small scale clay pot and porous capsule irrigation systems

x

Argentina, Bolivia, Ecuador, Panama, Dominican Republic.

· automatic surge flow and gravitational tank irrigation systems

x

Mexico.

· dual water distribution systems

x

Saint Lucia, U.S. Virgin Islands, Turks and Caicos Islands.

· other

x

x

x

Brazil, Chile, Jamaica, Venezuela.

Name of Technology: Rainwater Harvesting from Rooftop Catchments

1.1

Sector: Domestic water supply; some agriculture

Technology Type: Freshwater Augmentation

Technical Description: There are three components to a rainwater harvesting system: the collection area, the conveyance system, and the storage facility. The collection area is usually the individual rooftop of a house or other building. Large communal catchments including hillsides and airport runways may also be used. The conveyance system is a series of gutters that carry the rainwater from the collection area to the cistern. The cistern or storage facility varies from steel drums and polyethylene tanks of various sizes to underground concrete tanks. It could be a part of the home or constructed separately, above ground or subterranean. The amount of water that can be collected depends upon the effective area of the collection surface, the volume of storage, and the amount of rainfall.

Extent of Use: This technology is widely used in Latin America and the Caribbean, mainly for domestic purposes. In some Caribbean islands, such as the U.S. Virgin Islands, use of rainwater harvesting systems has been mandated by the government and the specifications for the systems are overseen by the national agency.

Operation and Maintenance: Operation requires little attention. Maintenance includes periodic cleaning, preferably with a chlorine solution; repair of occasional cracks in the cistern; regular cleaning of the gutters; and inspection to ensure that the system is free of organic matter.

Level of Involvement: Government participation varies in the different countries of Latin America and the Caribbean. In areas where the government regulates the design and use of the system, participation is high; elsewhere, participation is generally low. As long as the system remains inexpensive, community participation will increase.

Costs: Costs vary depending on the location storage facilities location and type of materials used. Costs can range from as low as $2 to $5/1 0001 collected. Generally, this is considered to be a very cost-effective technology.

Effectiveness of Technology: Rainwater harvesting is widely used, generally inexpensive, and very effective, especially in the Caribbean, where cisterns provide the principal source of water for many homes, and has been an excellent source of emergency water.

Suitability: Most suitable in arid and semi-arid regions with no public water supply. Suitability decreases as other sources of water supply become available.

Cultural Acceptability: Rainwater harvesting is widely acceptable.

Advantages:
· Rooptop systems are easy and, in general, inexpensive to construct, owner operated and managed.
· They are an essential back-up water supply in times of emergency.
· They often lead to better building foundations when cisterns are included in substructure.
· Rainwater quality may be higher than that of other water sources.
· Rainwater provides an excellent freshwater supply where surface and groundwaters are unavailable, scarce, or contaminated.

Disadvantages:
· Rainfall is not a dependable water supply source during droughts.
· Rainwater may be contaminated by animals and organic matter.
· The cost of constructing a home with a cistern is higher.
· Standing water in the cistern may provide potential breeding sites for mosquitoes; contaminated systems may create some health risks.
· In some cases, initial costs are higher.
· Public utility revenues may be slightly reduced.

Further Development of Technology: There is a need for better quality control of rainwater harvesting systems, for promoting rainwater harvesting as an alternative and supplement to utility water, for assistance in building large-capacity storage tanks, and for developing proper regulatory guidelines for cisterns.

Information Sources: Final Report of the Workshop on Alternative Technologies for Freshwater Augmentation in the Caribbean (Barbados, 24-27 October 1995), and Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Peru, 19-22 September 1995), OAS/UNEP.

Name of Technology: Rainwater Harvesting in situ

1.2

Sector: Agriculture and livestock

Technology Type: Freshwater Augmentation

Technical Description: This technology consists of using topographic depressions, either natural or artificial, to store rainwater where it falls for future use. Construction of furrows and raised beds is a normal practice in this technology.

Extent of Use: This technology is used extensively in northeastern Brazil, in the Chaco region of Paraguay, and in Argentina, primarily for livestock watering and agricultural purposes.

Operation and Maintenance: Once the area is properly prepared, little maintenance is required. Maintenance includes keeping the area free of debris and unwanted vegetation.

Level of Involvement: Government agencies and agricultural organizations are involved.

Costs: Principal costs are in preparing the site. Costs range between $180 and $2 000 in Brazil; and up to $4 500 in Paraguay.

Effectiveness of Technology: Rainwater harvesting increases water supplies for irrigation and livestock watering. In some cases, it has been used effectively for domestic supply.

Suitability: In arid and semi-arid regions of low topographic relief for cultivation and livestock watering.

Cultural Acceptability: This technology has been practiced for many years by the agricultural communities of Brazil, Paraguay, and Argentina, and should be accepted in other countries with similar topographic and climatic conditions.

Advantages:
· In situ harvesting requires little additional labor.
· Systems can be constructed prior to or after planting.
· In situ harvesting makes better use of rainwater for irrigation.
· Retaining water on-site provides flexibility in soil utilization.
· It also provides artificial recharge for aquifers.

Disadvantages:
· In situ harvesting cannot be implemented where the slope of the land is greater than 5%.
· It is difficult to implement on rocky soils.
· The area needs to be cleared and earthworks created.
· The technology works best in highly impermeable soils with natural topographic relief.
· Evaporation will decrease the effectiveness of water storage in low areas.

Further Development of Technology: There is a need for improvements in the equipment used for soil preparation and the development of new soil conservation practices.

Information Sources: Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru, 19-22 September 1995), OAS/UNEP.

Name of Technology: Fog Harvesting

1.3

Sector: Domestic water supply; agriculture and livestock; industrial

Technology Type: Freshwater Augmentation

Technical Description: The water in fog can be harvested through simple systems known as fog collectors. Factors to be considered when establishing a system include the fog water content, the frequency of fog in the geographic area under consideration, and the overall design of the system. Fog collectors are made of fine nylon net strung between poles in areas known to have frequent fogs. The nets face into the wind. These systems can be made up of individual panels, each with a surface area of up to 48 m², or they can be composed of a group of joined panels. Water droplets in the fog condense on the net and, when enough have gathered, coalesce and run off into a conveyance system which carries the water to a cistern or other storage area.

Extent of Use: This technology is primarily utilized in mountainous coastal regions with high levels of fog and recurring winds, such as those found in Chile, Peru, Ecuador, and Mexico. It also has been utilized in arid countries (such as the Middle East) around the world.

Operation and Maintenance: Maintenance includes tightening the nets, cables and cable fasteners periodically, cleaning or replacing the nets as wear occurs, and ensuring that the conveyance system and cisterns are free from contamination by cleaning periodically with chlorine and calcium chloride.

Level of Involvement: Community participation is recommended at all levels so that the shared maintenance costs are kept low and the users feel a sense of responsibility for the system. Government subsidies may be necessary, particularly in the early stages.

Costs: Costs vary from region to region. Often, the most expensive item is the conveyance system connecting the collection nets to the storage area. Installation costs average about $90 per m² of mesh, but may vary with the efficiency of the system, the pipeline length, and the size of the storage tank. Production costs in Chile are around $3/1 0001.

Effectiveness of Technology: Fog harvesting is one of the most effective water augmentation technologies for arid and mountainous areas (30% of the water contained in fog can be harvested). Its use, however, is limited by the length of the fog season and the capacity of storage tanks.

Suitability: In coastal, arid, mountainous regions where fog is common and other sources of water supply are not available.

Cultural Acceptability: This is a relatively new, largely experimental technology. Acceptability may be limited until its effectiveness has been demonstrated.

Advantages:
· Fog harvesters are easy to install and, in general, less expensive than most other sources of potable water.
· They can create viable communities in inhospitable areas.
· Water quality is better than existing water sources used for agricultural and domestic purposes.

Disadvantages:
· A pilot project must first be undertaken to evaluate the feasibility of fog harvesting in any given region.
· A back-up system is recommended in case fog conditions change.
· High costs may result from pipeline lengths required.

Further Development of Technology: The distribution system should be made more cost-effective; the design of the collectors needs to be improved and made more durable; and the community should receive basic information about this technology before it is implemented in order to utilize it effectively.

Information Sources: Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru, 19-22 September 1995), OAS/UNEP.

Name of Technology: Runoff Collection from Paved and Unpaved Roads

1.4

Sector: Agriculture

Technology Type: Freshwater Augmentation

Technical Description: Runoff from paved and unpaved roads can be collected in drainage ditches or street gutters, and stored temporarily. This water may then be transported through conduits and underground galleries to cultivation areas where it is used. In some cases, the water may be kept in swales and used for forestation projects along roadways. In some situations, the roadways themselves may be used as dikes for water diversion.

Extent of Use: This technology of runoff capture and storage has been used in semi-arid areas of Brazil, Argentina, and Venezuela, primarily for agricultural purposes.

Operation and Maintenance: Ditches and swales must be cleared of debris. Control of insects in standing water may be required.

Level of Involvement: Government participation is expected when the collected water is used for forestation. Private participation is common in the agricultural sector.

Costs: A forestation project in Argentina using water from 1 km of paved roadway cost $2 000. Costs are generally low and justifiable in terms of water supply benefits.

Effectiveness of Technology: Using water from this source, carob trees grew by an average of 30 cm/yr, while pepper trees grew by an average of 35 cm/yr, during the period between 1985 and 1995 in a plantation in Mendoza, Argentina.

Suitability: In arid and semi-arid regions where the runoff from the roadways is normally lost from the system.

Cultural Acceptability: Use of road runoff is well accepted by public works agencies in arid and semi-arid regions.

Advantages:
· Runoff collectors are easy to operate and maintain.
· Runoff collection may enhance the growth of native flora.
· It enhances the ability to cultivate lands in arid and semi-arid areas.
· Collectors have a low cost, especially if installed at the time the roadways are constructed.
· They may reduce erosion and sedimentation problems if properly designed and operated.

Disadvantages:
· Runoff-based systems may require irrigation of plants during the dry season and drought periods (i.e., a secondary water source).
· Irrigated areas and water storage areas need to be fenced to control animal grazing.
· The technology requires appropriate soil conditions to be implemented.
· Water collected from roadways may be contaminated by litter and debris deposited on road surfaces, and by chemical pollutants deposited by vehicular traffic, especially in urbanized areas.

Further Development of Technology: This technology should be combined with other runoff collection and storage technologies, such as in situ and regional impoundments, in order to be most effective.

Information Sources: Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru, 19-22 September 1995), OAS/UNEP.

Name of Technology: Runoff Collection using Surface and Underground Structures

1.5

Sector: Agriculture and livestock; domestic water supply, industry and mining

Technology Type: Freshwater Augmentation

Technical Description: There are two types of structures commonly used: local impoundments and dams. Local impoundments are storage ponds dug into the ground, while dams are designed to increase the storage capacity of areas of a river or stream by intercepting runoff and storing it for future use. Three types of dams are generally used: earth dams, rockfill dams, and concrete arch dams. Their use is typically dictated by the subsurface geology, available materials, and length of storage required. Local impoundments, in contrast, are often dug into the soil in naturally impervious areas, or lined with clay or other material so as to be made impermeable. The shape of the structures is usually rectangular or round. A filter or chlorinator unit should be added if the water in the impoundment is used for domestic supply. Construction site criteria for both types of structures are similar.

Extent of Use: Runoff collection has been used throughout Latin America and the Caribbean. Argentina, Brazil, Costa Rica, Ecuador, Panama, and Venezuela have built dams and impoundments to increase water supplies for domestic use and irrigation. Aruba and Suriname have also been involved in the development of similar projects.

Operation and Maintenance: Collection areas should be impermeable to avoid loss of water. Periodic testing of soil permeability is advisable. Control of sedimentation is necessary. Proper maintenance of instrumentation and the distribution system is required; operation and maintenance of the system by trained personnel is desirable.

Level of Involvement: Government participation is essential in the site selection, design, and construction of large projects; small projects may be built privately, but should be subject to government inspection and regulation. Large private organizations involved in hydroelectric power production or agricultural production may be substituted for governmental involvement in the construction and operation of these structures.

Costs: Costs vary depending on the size and type of the structure. In Ecuador, costs range between $0.10 and $2/m³ of water stored; in Argentina, costs range between $0.60 and $1.20/m³ of water stored. In Brazil, a 3 000 m³ project cost $2 000.

Effectiveness of Technology: The effectiveness of this technology is measured by the degree to which the technology meets demands for water through the additional storage provided: in Argentina, an increase in irrigation efficiency of between 5% and 15% was observed; in Brazil, a 90% increase in industrial water demand was met; and in Suriname, the availability of water increased tenfold while the saltwater wedge of the Suriname River moved 30 km downstream.

Suitability: In areas where the temporal and spatial distribution of rainfall is highly variable, and additional storage is required to meet demand.

Cultural Acceptability: This is a widely accepted technology, given preferential use, where applicable, by engineers and local communities.

Advantages:
· Runoff collection allows agricultural production in arid and semi-arid areas.
· Structures may provide a source of water for hydroelectric power production.
· The technology may promote and enhance the native flora and fauna of an area.
· Pollutants are generally diluted.
· Perennial flows may reduce salt water intrusion in coastal areas.
· Impoundments provide recreational opportunities.

Disadvantages:
· Dam construction requires the availability of land to be inundated, and suitable topography.
· Surface structures are subject to high evaporative losses.
· Structures require impermeable soils.
· Structures have high construction costs.
· There is a risk of flooding adjacent lands during wet periods.
· Dams may have significant environmental impacts both upstream and downstream, including alteration of flooding regimes, scour and sediment deposition patterns, and micro-climatic conditions.
· There is a risk of flooding due to dam failure.

Further Development of Technology: Research has improved the efficiency of dam and reservoir construction and operation techniques. Further improvements to reduce the costs of construction, especially of small schemes, and increase the efficiency distribution systems are required. Methods to reduce evaporative losses are needed.

Information Sources: Final Report of the Workshop on Alternative Technologies for Freshwater Augmentation in the Caribbean (Barbados, 24-27 October 1995), and Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru, 19-22 September 1995), OAS/UNEP.

Name of Technology: Flood Diversion

1.6

Sector: Agriculture and livestock

Technology Type: Freshwater Augmentation

Technical Description: Flood diversion structures are used to divert flood waters for water supply augmentation. Transverse dikes, small-scale diversion structures (toroba), and water traps are commonly used. Both transverse dikes and water traps are built of clay or other impermeable materials across portions of streams or rivers. The toroba, built of wooden poles, vegetation residue and logs, are used to divert stormwater runoff.

Extent of Use: Transverse dikes have been used in Sao Paulo State, Brazil; water traps have been used in the Province of Mendoza, Argentina; and toroba have been developed and used in the state of FalcVenezuela.

Operation and Maintenance: Diversion structures are generally simple to operate. Maintenance is required to repair diversion structures, especially after heavy rainfalls. Extremely large flood events may require replacement of the structures. Mitigation of erosion is necessary, especially in the vicinity of wing walls.

Level of Involvement: Small-scale structures can be constructed by local communities with technical support from government or large private enterprises. Dikes and water traps require government and private-sector involvement.

Costs: The cost of dikes varies from about $10 000 to several millions, depending on the scale of the project. Water traps for small projects in Argentina have an estimated cost of $ 130 to $ 170. The toroba, being constructed of natural materials, have a negligible cost.

Effectiveness of Technology: In addition to providing water supply as needed, this technology has been successful in reducing erosion and increasing groundwater recharge.

Suitability: In large river basins where sufficient volumes of water can be diverted.

Cultural Acceptability: This is a widely accepted technology for water supply augmentation and erosion control among engineers. Its acceptance among local communities is variable.

Advantages:
· Diversion to storage makes use of flood waters.
· Structures provide a basis for sedimentation and erosion control when properly operated.
· Structures may serve as a source of groundwater recharge.
· Structures reduce water velocities in streams.
· This technology may contribute to biodiversity protection and ecosystem restoration,
· The retention of soils may improve soil fertility.

Disadvantages:
· This technology is disruptive to vegetation cover during construction.
· Structures may fail or be damaged when subjected to conditions that exceed design storm conditions.
· Structures may have adverse environmental impacts on aquatic flora and fauna.

Further Development of Technology: Additional data collection is needed to improve structure performance. Educational programs to encourage the use of this technology as a river basin management tool should be implemented.

Information Sources: Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru, 19-22 September 1995), OAS/UNEP.

Name of Technology: Water Conveyance by Marine Vessels

1.7

Sector: Domestic water supply

Technology Type: Freshwater Augmentation

Technical Description: Water transport by marine vessels is used when water must be moved between islands or across the sea. Barges are a very efficient means of transportation, but storage tanks must be (1) properly sized so that shipping costs are effective, and (2) properly designed to prevent surges during transportation. The barges are usually pulled by tugs. Once the destination is reached, the storage tanks are emptied and water is either pumped directly into the distribution system or distributed to consumers on tanker trucks.

Extent of Use: This technology is suitable for all regions as long as there is adequate space along the shoreline for the barge to unload and onshore for the facilities needed to store and distribute the water to consumers. Barging of freshwater using marine vessels has been used to augment supplies in Antigua, the Bahamas, and other Caribbean islands.

Operation and Maintenance: The biggest factors influencing this system are inclement weather and mechanical failure. Each of these causes the loss of several working days a year in a typical barge operation. Also, machinery often needs to be replaced, which leads many owners to carry duplicate parts in the event of a breakdown. Generally, skilled personnel are not required, apart from the barge pilot.

Level of Involvement: The costs involved in this technology are so high that only public utilities, government agencies, or companies that have a high number of consumers, such as resorts or industries, can afford to use it.

Costs: Costs of water conveyance by marine vessels are high compared to other systems. However, if large quantities are shipped on a regular basis, costs decline. Also, creating the distribution infrastructure can be quite expensive if some component is not already in place. Estimated costs of shipping water to the Bahamas are $5.80/1 000 gal. shipped (including fuel).

Effectiveness of Technology: Due to its high cost, shipping freshwater has had mixed results. Some countries have had less expensive and better results with desalination while other countries have found it less costly to build the necessary infrastructure to supply all their domestic water needs by transported water.

Suitability: On small islands where marine vessels are readily available and water is scarce.

Cultural Acceptability: Not widely acceptable, in view of the high costs, compared with other technologies.

Advantages:
· This technology has a short start-up time (3-6 months).
· It does not require highly skilled personnel.
· It is not as expensive as desalination plants.

Disadvantages:
· Weather has a big impact on efficiency.
· The cost of transportation is high, often prohibitively so.
· Product quality is not guaranteed.
· This technology needs an adequate distribution infrastructure.

Further Development of Technology: Infrastructure must be developed for distribution. However, it is difficult to justify this cost when most countries rarely use this technology.

Information Sources: Final Report of the Workshop on Alternative Technologies for Freshwater Augmentation in the Caribbean (Barbados, 24-27 October 1995), OAS/UNEP.

Name of Technology: Water Conveyance by Pipelines, Rural Aqueducts, and Water Tankers

1.8

Sector: Domestic water supply; agriculture; industry and mining

Technology Type: Freshwater Augmentation

Technical Description: Conveyance of water by pipelines involves the transfer of water from ground and surface water sources in an area where the available resources exceed demand to an area where demand exceeds available resources. The system of conveyance may be gravity-flow or pumped.

Extent of Use: Water conveyance in pipelines, rural aqueducts, and tanker trucks is found throughout Latin America and the Caribbean. Water tankers are utilized primarily in areas served by aqueducts. Interbasin transfer schemes using pipelines have been used in Jamaica and Panama to supply water to rural areas.

Operation and Maintenance: Maintenance of aqueducts requires some technical skills and periodic repairs and cleaning of the system.

Level of Involvement: Water distribution projects have a high level of government participation. Planning and design of these systems usually involves private consultants. Community participation may be required in the operation and maintenance of the systems.

Costs: Costs vary depending on the complexity of, and materials used to construct, the system.

Effectiveness of Technology: The technology is very effective in Jamaica and Panama, where 30% to 40% of the water used in one basin is transferred from an adjacent basin.

Suitability: In regions where there is an "excess" of water in one area and a "deficit" in another; this situation is common in many countries.

Cultural Acceptability: It is a well-accepted technology in areas with insufficient water supply.

Advantages:
· Water tankers are less complex than other systems.
· Pipelines and rural aqueducts allow for large shipments of water, can improve irrigation, and can transform previously underdeveloped areas into potential areas for agroindustrial enterprise development.

Disadvantages:
· Prices of water from water tankers are high.
· Water tankers require adequate road infrastructure.
· Pipelines involve high capital costs, and require skilled workers.
· Interbasin transfer could cause environmental impacts.

Further Development of Technology: Development of improved, low-cost pipe materials would increase the use of this technology. Better quality control and training of local users is necessary.

Information Sources: Final Report of the Workshop on Alternative Technologies for Freshwater Augmentation in the Caribbean (Barbados, 24-27 October, 1995), and Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru, 19-22 September 1995), OAS/UNEP.

Name of Technology: Artificial Recharge of Aquifers

1.9

Sector: Domestic water supply; agriculture

Technology Type: Freshwater Augmentation

Technical Description: There are several different artificial recharge techniques used in Latin America and the Caribbean: infiltration basins and canals; water traps; cutwaters; surface runoff drainage wells; septic tank system effluent disposal wells; and the diversion of excess flows from irrigation canals into sinkholes. Infiltration canals utilize high circulation velocities to eliminate waste buildup, resulting in higher infiltration rates. Water traps are designed for use under conditions of infrequent rainfall and are used to increase productivity in-situ. Cutwaters are excavations built on top of permeable strata in areas without rivers or creeks. Drainage wells divert runoff for storage purposes. Soak-aways utilize wastewater discharged from septic tanks. Sinkhole injection of excess flows diverts water flow into a reception basin, where the water is treated and recharged.

Extent of Use: The different variations of this technology have been widely used throughout Latin America and the Caribbean. Use will most likely increase as water demands increase and surface water resources become less available.

Operation and Maintenance: Most of the techniques require minimal maintenance. However, sinkhole injection systems can require extensive cleaning and repairs.

Level of Involvement: There is extensive participation by both governments and the private sector in the implementation of this technology. Generally, the government provides financing and technical expertise, while the private sector is responsible for the initial development and maintenance of the technology once it is in place.

Costs: The reported costs of infiltration basins is $0.20/m³, while water traps in Argentina have been reported to cost between $133 and $167 per trap. The initial capital cost of a cutwater has been estimated at $6 300 for a 5 700 m³ cutwater; maintenance costs for cutwaters tend to decline with time. The initial capital cost of a sinkhole-based application in Jamaica was approximately $ 15000, with maintenance costs estimated at $ 6000.

Effectiveness of Technology: All of the technologies have been successfully utilized over the years in different regions. Some have been particularly successful in arid regions. The low cost and low maintenance requirements make this an attractive option. In addition, the salinity in aquifers is often reduced, thereby leading to a wider range of uses for the water.

Suitability: Some variations are better suited to specific climatic zones: water traps are successful in arid regions; cutwaters, because they are primarily used in conjunction with rainwater, are successful in more humid areas; and the utilization of sinkholes as injection points is most successful in karst areas.

Cultural Acceptability: There are no cultural limitations on the use of these technologies. They are a well-accepted practices.

Advantages:
· The techniques are easy to master and easy to operate.
· Additional materials to extend or augment these systems are relatively cheap.
· The technology can improve aquifer water quality, even reducing salinity.
· It is advantageous in arid regions, where surface water resources are scarce.
· It has a low cost and requires low maintenance.

Disadvantages:
· Wells are often not maintained.
· There may be high nitrate levels in the groundwater, especially in agricultural areas.
· Aquifers may be degraded if the quality of injected water is poor.
· Sustained use of water from aquifers may not be economically feasible unless they can be recharged.
· Use of water from aquifers may deplete the water table and destroy local soils and vegetation.

Further Development of Technology: The system design should be improved to eliminate the possibility of contamination and increase recharge efficiency; there should be greater knowledge of sedimentation processes.

Information Sources: Final Report of the Workshop on Alternative Technologies for Freshwater Augmentation in the Caribbean (Barbados, 24-27 October 1995), and Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru, 19-22 September 1995), OAS/UNEP.

Name of Technology: Groundwater Pumping Using Non-Conventional Energy Sources

1.10

Sector: Domestic water supply; agriculture

Technology Type: Freshwater Augmentation

Technical Description: A variety of water pumps use non-conventional energy sources. These include hydraulic pumps, windmill-driven pumps, and photovoltaic pumps. The hydraulic pump uses the hydrologic energy from streams. Hydraulic rams work by altering water pressures to elevate water to a higher level. The rope pump is attached to a pipe axis, which rotates by turning a handle. Handpumps are widely utilized and can be placed above or below ground and operate in much the same way as the rope pump. Windmill-driven pumps use wind power to turn a rotor, which, in turn, moves the pump pistons. Photovoltaic pumps utilize solar radiation to power the electric pump motors.

Extent of Use: Non-conventional energy sources are used throughout both Latin America and the Caribbean to pump water. The technique used varies according to local topographical and geological conditions. The hydraulic pump is primarily limited to high volume rivers, while the hydraulic ram, rope pump, and windmill pump can be easily adapted to most conditions. In contrast, the photovoltaic pump needs an area with consistent and high irradience. Honduras, with its varying terrain and high levels of sunlight, provides ideal conditions for the use of photovoltaic pumps.

Operation and Maintenance: The operation of most of these pumping systems does not require highly skilled personnel or a high level of maintenance. However, most of the systems require frequent oiling and protection of exposed metal surfaces, as well as valve cleaning. Photovoltaic systems may require new parts and frequent checks.

Level of Involvement: Central governments have had little involvement in supporting non-conventional pumping technologies. The primary participants are local communities and NGO's, which have provided the necessary technical and financial support.

Costs: The capital cost of the hydraulic ram pump increases in proportion to the size of the pump. The average initial cost of a windmill pump is from $800 to $1 000, while the photovoltaic pump requires an initial investment of $6 000 to $ 12 000. Given the high costs and lack of government funding for some of these techniques, the extent of utilization is restricted in many areas.

Effectiveness of Technology: The yield of the rope pump depends on the user's physical condition. The windmill pump's efficiency is in direct proportion to the speed of the wind (higher wind speeds yield higher output).

Suitability: In areas where conventional energy sources such as fossil fuels are scarce, expensive, or unavailable.

Cultural Acceptability: Widely accepted in most rural areas.

Advantages:
· These pumps have low installation and maintenance costs.
· They have a negligible environmental impact.
· Rope pumps do not require skilled labor and have low contamination levels.
· Windmill-driven pumps are easy to install and can withstand inclement weather.
· Photovoltaic pumps are easy to install, reliable, long-lasting, and adaptable, having low maintenance and a readily available energy source.

Disadvantages:
· Hydraulic pumps may suffer damage due to their proximity to river beds and currents.
· Hydraulic rams are limited to small irrigation areas.
· Rope pumps cannot lift water higher than the surface of the well.
· Windmill-driven pumps cannot easily extract water from depths greater than 20 m.
· Replacement parts for photovoltaic systems are usually imported, making repairs difficult and costly.
· Initial and maintenance costs of photovoltaic pumps are high.

Further Development of Technology: People should be trained in the use and maintenance of these pumps; the design of the connections should be improved; quality control mechanisms should be developed; and corrosion resistance of exposed parts needs to be enhanced.

Information Sources: Final Report of the Workshop on Alternative Technologies for Freshwater Augmentation in the Caribbean (Barbados, 24-27 October, 1995), and Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru, 19-22 September 1995), OAS/UNEP.

Name of Technology: Desalination by Reverse Osmosis

2.1

Sector: Domestic water supply; industry and mining; agriculture

Technology Type: Water Quality Improvement

Technical Description: Desalination reduces the salt content of saline water to minimal levels, generally less than 1 000 mg/l. Suitable saltwater sources are seawater and brackish water. Reverse osmosis forces saline water through a semi-permeable membrane, which removes salt ions from the water. A concentrated salt solution remains on one side of the membrane while pure water collects on the other side. Energy is required to create the pressure needed to force saline water through the membrane. There are two by-products of desalination using reverse osmosis: brine and pure water. Brine may be discharged into aquifers or diluted with effluent and sprayed over golf courses or other public areas. Pure water can be used for domestic, agricultural, or industrial purposes.

Extent of Use: Desalination plants exist in many Caribbean countries and in many rural areas of South America. On many Caribbean islands, desalinated water has become the main source of drinking water. However, the expansion of this technology remains limited due to the high energy costs involved.

Operation and Maintenance: Day-to-day monitoring by trained personnel is required. The most important maintenance required includes repair and adjustment of pumps; cleaning and replacement of membranes and filters; calibration of instruments; replenishment of the necessary chemicals; and acquisition and maintenance of an inventory of parts for the system.

Level of Involvement: Due to the high costs involved, only public water supply companies with large numbers of consumers, and industries, have undertaken desalination. In most cases, government involvement includes paying for land, taxes, and providing assistance in plant operations.

Costs: Costs depend on the location, plant size, and type of water being desalinated (seawater being the most expensive). Other major costs, apart from the high initial capital investment, include energy, replacement parts, and skilled labor to operate the plants. In the Bahamas production cost ($/m³) ranges between 4.60 and 5.10. In rural areas of Brazil, 0.12 to 0.37.

Effectiveness of Technology: Over time, reverse osmosis systems have become more efficient, and improvements in desalination technology have reduced costs. The technology is being increasingly used by the industrial sector. Current reverse osmosis membranes can separate 98% of the salt from water with a dissolved solids level of 25 000-30 000 mg/l, using pressures of 13.6 to 19.0 atm. These membranes are guaranteed to work for five years before requiring replacement.

Suitability: In coastal areas and on small islands where other conventional methods are not practicable.

Cultural Acceptability: This is an expensive technology, generally acceptable in situations where economic necessity dictates its use.

Advantages:
· A reverse osmosis plant is a simple, prepackaged system that can be easily installed.
· Operation and maintenance costs are low when the system is properly utilized.
· The water source is "unlimited".
· Inorganic contaminants can be easily removed.
· Plant size can easily be expanded.
· The system has a negligible environmental impact if brine is properly disposed of.

Disadvantages:
· The membrane may fail if not maintained properly.
· Inclement weather may interrupt the desalination process.
· Reverse osmosis requires a high level of material, equipment, and spare part support which may not be locally available.
· Brine must be disposed of.
· Reverse osmosis plants require a dependable energy source.
· This technology is expensive when compared to other technologies.

Further Development of Technology: This technology can be improved by developing higher quality membranes, capable of operating at lower pressures and less susceptible to clogging than the present, high pressure systems; by making the systems easier to operate; and by employing combination technologies such as the reliable and low-cost centrifugal reverse osmosis system developed in Canada.

Information Sources: Final Report of the Workshop on Alternative Technologies for Freshwater Augmentation in the Caribbean (Barbados, 24-27 October 1995), and Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru, 19-22 September 1995), OAS/UNEP.

Name of Technology: Desalination by Distillation

2.2

Sector: Domestic water supply; industry and mining; agriculture

Technology Type: Water Quality Improvement

Technical Description: Distillation separates freshwater from saline water by heating it until water vapor is produced. The water vapor is then condensed to produce freshwater. In distillation plants, boiling occurs at lower temperatures than "normal" by manipulating pressures and recycling heat through the interchange of condensation heat and vaporization heat. There are three major types of distillation processes: multiple-stage flash processes (MSF), multieffect distillation processes (MED), and vapor compression processes (VP).

Extent of Use: Distillation plants are used in the Caribbean, particularly in the U.S. Virgin Islands and Cura, and in some Latin American countries mainly to provide potable water to local communities and for industrial purposes.

Operation and Maintenance: This technology requires skilled personnel and high levels of maintenance. Maintenance includes repair of cracks in the system; removal of biological growth in the system; cleaning and inspection of the vacuum system, pumps, and motors; and the addition of anti-corrosive chemicals to the water to avoid corrosion and equipment breakdown.

Level of Involvement: Participation in this technology has been limited to use in the private sector by some foreign firms. As a consequence, most of the water processed by distillation is used industrially. Costs are still too high for more general use by government utilities. However, it is expected that this technology could spread rapidly if costs are lowered.

Costs: Costs vary depending on the type of distillation process used, plant capacity, salinity level, and the skill level of local personnel. Costs usually increase when plant size increases. Current distillation costs reportedly range between $1.47/m³ in Chile and $4.31/m³ in The Netherlands Antilles.

Effectiveness of Technology: The multi-stage flash process (MSF) is generally considered to be more effective than distillation by reverse osmosis. Although desalination is fairly expensive compared to other methods of obtaining freshwater, it is very efficient when properly maintained, producing water of high quality.

Suitability: This technique is used in the Middle East, North Africa, and the Caribbean. However, plant operation and implementation is limited by the lack of fuel, chemicals, spare parts, and trained personnel.

Cultural Acceptability: This technology is generally viewed as highly technical and expensive. It is acceptable for small projects of limited scope located near the coast.

Advantages:
· Distillation plants can be fully automated and, except for brine disposal, have a minimal environmental impact.
· When they are operated properly, maintenance costs are low.
· Low temperature distillation reduces energy requirements and production costs.
· High quality water can be produced.

Disadvantages:
· Some techniques require large energy inputs, regardless of plant size.
· Brine disposal may be a problem.
· Distillation requires a high level of technical skill and training.
· Distillation requires the use of chemicals and other materials which must be handled carefully.

Further Development of Technology: Future development includes reduced costs and improvement of system efficiency; reduction in required operating temperatures; ensuring a high level of thermal efficiency; and reduction of overall energy costs.

Information Sources: Final Report of the Workshop on Alternative Technologies for Freshwater Augmentation in the Caribbean (Barbados, 24-27 October 1995), OAS/UNEP.

Name of Technology: Clarification using Plants and Plant Material

2.3

Sector: Domestic water supply

Technology Type: Water Quality Improvement

Technical Description: Two applications of native plants are used to improve water quality. Bean, peach, or coconut seeds are used to prepare solutions that act as coagulant or clarifying agents. The second application involves the use of aquatic plants such as cattails, totora, water hyacinths, and duckweeds in wetland ecosystems to purify water and treat wastes. Aquatic plants can absorb many chemical compounds and remove suspended solids. For this system, 1 m² of plants is required for each m³/day of water treated. Factors to be considered when designing the system include the volume and flow rate of water to be treated, the initial concentrations of chemicals in the water, the desired water quality of the effluent to be discharged, and any subsequent use of the treated water.

Extent of Use: The use of native plant materials for water treatment is prevalent throughout Central and South America for treatment of river water for domestic use. Aquatic plants are a low-cost, low-energy system that is particularly well suited to hot climates. A number of water-hyacinth-based systems are being used in Mexico to remove chemical contaminants from water, and totora is used in both Bolivia and Peru to treat wastewater from small communities. Wetland systems may have potential for treating wastewater from larger communities. Wetlands may also be of use as a means of pretreating surface waters prior to use for domestic supply.

Operation and Maintenance: Operation and maintenance are simple and there are few requirements. The totora treatment system may require infrequent harvesting plants or dredging the sediments; the water-hyacinth-based system requires regular removal of excess plants and the addition of a low levels of chlorine to disinfect the effluent. In wetlands, mosquito breeding should be avoided. This is easy to do if personnel are aware of mosquito habitats.

Level of Involvement: This technology is utilized primarily by the private sector in rural areas, and by universities and governments for research and development purposes. Some governments have dedicated financial and technical resources to the development of aquatic plant systems for wastewater treatment.

Costs: There is little information on the seed treatment systems. The main cost involves acquiring the seeds. The costs for implementation, operation, and management of the totora system range from insignificant in Bolivia to $65 000 per system in Peru. The cost of wetland treatment systems rises in proportion to the amount of wastewater treated.

Effectiveness of Technology: Seed treatment has proved particularly effective in the clarification of turbid waters. In general, the higher the initial turbidity, the higher the rate of removal. With aquatic plants, heavy metals can be removed very quickly, while the absorption of other elements may require a longer retention time.

Suitability: In areas with concentrations of plants having coagulant properties and/or areas where wetlands exist or can be established.

Cultural Acceptability: There are no cultural barriers to the use of this technology.

Advantages:
· This technology has a very low cost, and is easy to implement and use.
· It is easy to construct and generally requires a small surface area, depending on the volume of water or wastewater to be treated.
· Plants can absorb heavy metals.
· Wetland systems can produce fertilizer (mulch), economically important plant materials, and animal food supplements.

Disadvantages:
· Plant seeds may not be readily available.
· Totora systems may require high initial investments.
· Aquatic systems need appropriate climatic conditions, sometimes requiring construction of a greenhouse.
· Metals or toxic substances may accumulate in the plants and require proper disposal.
· Water hyacinth may grow too quickly, clogging waterways or creating stagnant water which fosters mosquito breeding.

Further Development of Technology: Research should be conducted to identify similar qualities in other species of plants, and to improve the efficiency of the plants after several cleanings. The appropriate density of aquatic plants for treating certain types of waters should be determined.

Information Sources: Final Report of the Workshop on Alternative Technologies for Freshwater Augmentation in the Caribbean (Barbados, 24-27 October 1995), and Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en America Latina (Lima, Peru, 19-22 September 1995), OAS/UNEP.

Name of Technology: Disinfection by Boiling and Chlorination

2.4

Sector: Domestic water supply

Technology Type: Water Quality Improvement

Technical Description: Disinfection of water for domestic purposes can be accomplished by boiling or chlorination Boiling kills most of the pathogenic organisms that cause waterborne diseases Chlorination of water may be accomplished by several methods In gas chlorination, a chlorinator meters the gas flows and mixes it with water The mixture is injected into wastewater to disinfect it A floating chlorinator has also been developed which administers doses of hypochlorite tablets However, the safety of the resulting water has been questioned As a result, gas chlorinators are more common Hypochlorination uses a chemical metering pump to inject chlorine solutions of different strengths into wastewater The dosing rate is constant and the hypochlorinator can operate under pressures as great as 100 psi.

Extent of Use: Boiling is applicable at the household level, and it is considered a short-term or emergency method As for chlorination, this method is practiced throughout the world Because chlorine is available at low cost, easy to use, and easy to procure, it is the most common system of disinfection in the Caribbean Usually, it is recommended that chlorine be manufactured locally This may constitute a limitation on its use, especially when using seawater, since seawater contains heavy metal ions which interfere with the stability of the chlorine solutions produced

Operation and Maintenance: Periodic cleaning and replacement of flasks, adjustment of dosage levels and checking the residual chlorine levels, periodic replacement of chemicals, and clearing of the tubing of all sludge and crusts are required

Level of Involvement: Boiling is used at the individual level only Small chlorination systems are managed by the private sector, while medium-sized systems or larger usually involve a public utility company Large systems sometimes require government involvement

Costs: Boiling costs depend on the cost of the energy used Chlorination systems vary depending on the location and the type of system used gas chlorination systems are usually more expensive than hypochlorination systems Generally, costs increase in proportion to the amount of water treated

Effectiveness of Technology: Boiling is recommended only as secondary technology Chlorination efficiency depends on the initial quality of water being chlorinated and the chlorination method used Gas chlorination is more efficient However, hypochlorination is preferred by users since it is easier to use

Suitability: Boiling is most suitable in rural areas where more sophisticated treatment methods are not available, and/or in case of emergency Chlorination is considered universally suitable

Cultural Acceptability: A widely accepted technology, recognized especially as a means of preventing the spread of waterborne diseases

Advantages:
· Boiling is a simple and effective means of disinfecting small amounts of water for personal consumption
· Chlorination systems are easy to construct, reliable, and affordable
· Floating chlorinators may be adapted for small communities
· Dosages and amounts of residual chlorine can be controlled in gas chlorinators

Disadvantages:
· Boiling requires considerable energy
· Chlorine gas is corrosive and potentially fatal in large quantities
· Chlorination may form potentially carcinogenic chlorinated hydrocarbons
· Chlorine oxidizes ammonia and other metals, and can cause explosions if not properly handled
· Hydrochlorinated compounds can cause fires when they come in contact with organic materials

Further Development of Technology: Chlorination technologies can be improved through improved handling and distribution methods, utilization of other compounds not as reactive as chlorine, and development of more cost-effective processes

Information Sources: Final Report of the Workshop on Alternative Technologies for Freshwater Augmentation in the Caribbean (Barbados, 24-27 October 1995), and Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru, 19-22 September 1995), OAS/UNEP

Name of Technology: Filtration

2.5

Sector: Domestic water supply use

Technology Type: Water Quality Improvement

Technical Description: Filtration systems are used to purify water for domestic consumption. There are several types of filters in use throughout Latin America and the Caribbean, including residential filtration systems, slow and rapid sand filtration systems, quarry filters, and vertical-flow filtration systems. Residential filters for household use are made with local materials, and partially remove contaminants. Slow sand filters are boxes with a layer of sand which can process between 2.5 and 6.0 m³/m²/day. Rapid sand filters can process 50 times as much water as slow sand filters.

Extent of Use: Filters are widely used throughout Latin America and the Caribbean in areas where poor quality water can cause waterborne diseases if not treated. The types of filtration systems used depend on local conditions. Most areas use a combination of filter types.

Operation and Maintenance: Most filters have low maintenance requirements, and only need periodic changing or cleaning of the filtering medium. Rapid sand filtration plants are more complicated and require constant monitoring by trained personnel who must backwash the filters for optimal performance.

Level of Involvement: The technology is often introduced by governments or NGOs. Implementation involves the entire community. In many countries, the private sector has also become involved in implementation.

Costs: Costs of residential filters vary according to size. Slow sand filters and rapid sand filters generally decrease in construction and maintenance costs as filter size increases to serve larger populations. Construction costs of sand filters average between $7 (rapid sand filters) and $22 (slow sand filters) per capita of population served for populations of 500 to 2 499; and between $3 (rapid sand filters) and $7 (slow sand filters) per capita of population served for populations greater than 50 000.

Effectiveness of Technology: Filters vary in efficiency in decreasing the level of contamination in the water. Residential filters may pass some contaminants after treatment, whereas quarry filters can remove up to 90% of the bacteria. Sand filters have generally proved most effective at slower filtration rates, with up to 99% of the bacteria being removed. In vertical-flow pre-filters, turbidity and color reductions are in the ranges of 23% to 45% and 34% to 56%, respectively.

Suitability: In most regions, but primarily in urban and rural areas where water quality is poor.

Cultural Acceptability: This technology is well accepted as an effective method of treatment at the household and municipal levels.

Advantages:
· Filters have a low construction cost, and are easy to install and operate.
· In general, there is little or no chemical use or power source required.
· Skilled personnel are not usually required.
· Filters adequately meet local household needs.
· They have minimal environmental impacts.
· Large quantities of washwater are not needed.

Disadvantages:
· Filtering media may not be available locally.
· Some filtration methods require skilled personnel.
· Some filtration methods require pre-treatment.
· Sand filters must be washed; a backwash facility is needed and some sand may need to be stored before it can be washed.
· There may be a lack of quality control in rural areas.
· Filtration is not effective for highly contaminated water, or water contaminated with dissolved substances.

Further Development of Technology: A more efficient filtration medium needs to be researched and developed; educational programs should also be implemented in rural areas to encourage the use of disinfectants with filtration systems.

Information Sources: Final Report of the Workshop on Alternative Technologies for Freshwater Augmentation in the Caribbean (Barbados, 24-27 October 1995), and Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru, 19-22 September 1995), OAS/UNEP.

Name of Technology: Wastewater Treatment Technologies

3.1

Sector: Agriculture; landscape irrigation; industry, and mining

Technology Type: Wastewater Treatment and Reuse

Technical Description: Wastewater treatment technologies can be categorized into three main groups: mechanical, aquatic, and terrestrial. Mechanical treatment systems require mechanical devices to perform the treatment function and include technologies such as oxidation, extended aeration, sequencing batch reaction, and trickling filtration. Aquatic treatment systems use lagoons or wetlands as the fundamental treatment unit and include technologies such as facultative lagoons, aerated lagoons, and hydrograph-controlled holding ponds, and may occur in combination with sand filtration systems, constructed wetlands, and aquaculture systems. Terrestrial systems involve the use of large parcels of land to treat wastewater by infiltration and include technologies such as slow-rate infiltration, rapid infiltration, overland flow, and subsurface infiltration systems. Other methods commonly used include activated sludge, biological vertical reactors, and septic tank systems. Most of these systems are aerobic, although some, such as septic tanks and anaerobic filtration systems, are anaerobic. Facultative lagoons and some activated sludge systems are both aerobic and anaerobic, the former being aerobic at the surface and anaerobic at the bottom, and the latter alternating aerobic and anaerobic sludge tanks.

Extent of Use: These technologies have been extensively used in most Latin American and Caribbean countries. Argentina, Bolivia, Brazil, Colombia, Cura, Chile, Jamaica, Mexico, and Saint Lucia have used different types of terrestrial and aquatic treatment systems, usually combined with wastewater reuse technologies. Chile, Colombia and Barbados have activated sludge plants, while Brazil has used biological vertical reactors.

Operation and Maintenance: Most of the systems require careful operation and some degree of maintenance, including preventive maintenance. Periodic cleaning, removal of algae and oily materials, and disposal of dried sludges are necessary in most systems. Wetland systems require periodic removal of plants and sediments. If hydroponic cultivation is practiced, use in combination with a dual water use technology is recommended.

Level of Involvement: Government involvement is essential in the implementation of most of these technologies. The private sector, particularly the tourism industry, has used treatment plants in conjunction with water reuse technologies. Selection and construction of appropriate technologies is usually initiated by government, with operation and maintenance being undertaken by the private sector.

Costs: Capital costs of these systems vary depending on the degree of mechanical complexity. Treatment plant costs range between $3 and $11/gal/day of wastewater treated. Lagoon system costs range from $1 to $5/gal/day. Terrestrial system costs range from $4 to $8/gal/day.

Effectiveness of Technology: Aerobic technologies effectively remove 90% to 95% of the biological oxygen demand (BOD) and suspended solids. Anaerobic technologies remove between 25% and 60% of the BOD and suspended solids. Wetland systems and hydroponic cultivation systems remove between 65% and 75% of the organic matter.

Suitability: Mechanical treatment systems are suitable in urban areas and for regional use in areas where space is a constraint. Aquatic and terrestrial systems are suitable in areas where space is available.

Cultural Acceptability: Most Latin American countries do not recognize the need to treat wastewaters for the protection of their natural and water resources.

Advantages:
Mechanical treatment systems have:
· High treatment efficiencies.
· Minimal land requirements.
· A wide range of applicability in communities of various sizes.

Disadvantages:
Mechanical treatment systems have:
· High capital costs.
· A need for sludge disposal.
· A need for qualified human resources for optimal operation and maintenance.
· High energy requirements.

Aquatic treatment systems have:
· Low capital costs.
· Low operation and maintenance costs.

Aquatic treatment systems have:
· A requirement for a large land area.
· Undesirable odors under certain conditions.
· A need for some mechanical devices, depending on the topography of the treatment plant site.
· A need for further development prior to large-scale application.

Terrestrial treatment systems have:
· The potential to provide groundwater recharge.
· Low operation and maintenance costs.
· A requirement for a low level of technically trained human resources.
· An ability to be incorporated into water reuse schemes.

Terrestrial treatment systems have:
· A requirement for a large land area with permeable soils.
· A requirement for the establishment of a suitable, water-tolerant vegetative cover to extract nutrients and retain soils on site.
· High initial costs.
· Relatively low efficiencies of treatment.

Further Development of Technology: New advances in wastewater treatment technologies are under way to improve efficiencies and reduce costs. Their application in situations requiring complex treatment in developing countries requires further analysis.

Information Sources: Final Report of the Workshop on Alternative Technologies for Freshwater Augmentation in the Caribbean (Barbados, 24-27 October 1995); Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru, 19-22 September 1995), OAS/UNEP; Ernesto Perez, Technology Transfer Chief, USEPA, Atlanta, Georgia, U.S.A.

Name of Technology: Wastewater Reuse Systems

3.2

Sector: Agriculture; landscape irrigation; industry and mining

Technology Type: Wastewater Treatment and Reuse

Technical Description: Wastewater reuse technologies produce an effluent suitable for irrigation or industrial purposes. Secondary treatment is the minimum requirement for the reuse of wastewaters for irrigation of food crops that are to be processed, and for irrigation of lawns and golf courses. Caution is required to avoid contamination of potable water wells. Additional nitration and chlorination/disinfection is required if wastewaters are used for irrigation of pastures and unprocessed food crops. A distribution system is usually required to convey the treated wastewaters from the wastewater treatment facility to the areas of reuse. Cross-contamination between distribution systems conveying potable water and treated wastewater should be avoided.

Extent of Use: This technology is commonly used by resort hotels in the Caribbean islands to irrigate golf courses. Treated wastewaters have been used in Chile for agricultural irrigation, and in Brazil as cooling waters for mining operations.

Operation and Maintenance: Operation and maintenance is minimal and primarily related to the distribution system and the wastewater treatment facilities. Clogging of pipes can be a problem; cleaning of pumps and filters is more frequent when using wastewater as a raw supply.

Level of Involvement: Primarily used in the private sector; encouragement of wastewater reuse by the government is necessary. Government is involved in the setting of guidelines for water reuse and monitoring its performance, primarily to avoid public health impacts.

Costs: Cost savings may be expected from the use of this technology, although cost estimates have not been reported. Expenses are related to operation of the treatment facilities and the need for a dual distribution system.

Effectiveness of Technology: The effectiveness of this technology is in the improvement of water quality in natural watercourses where wastewater was previously discharged. In Jamaica, significant reductions in BOD, nutrient concentrations, and faecal coliform levels occurred when wastewater reuse was implemented at a resort hotel.

Suitability: For applications such as watering of golf courses and lawns, cooling of industrial and mining equipment, and irrigation of non-edible crops.

Cultural Acceptability: A large percentage of domestic water users are afraid of using reclaimed wastewater, primarily for health reasons. Time, public information, and successful experimental applications will be needed before this technology is widely implemented.

Advantages:
· Demand for potable water drawn from raw water sources is reduced.
· Smaller treatment facilities are required.
· Environmental impacts associated with wastewater discharges are reduced.
· Water pollution of freshwaters and coastal waters is reduced.
· Capital costs are relatively low.
· Operation and maintenance requirements are simple.
· Reuse facilitates frequent watering of lawns, golf courses, and non-edible crops in water-scarce areas.

Disadvantages:
· Reuse can result in groundwater contamination.
· Human contact with irrigated effluents can cause skin irritations and other public health problems.
· Reuse requires installation of a second distribution system, which increases capital and operation and maintenance costs.
· It is inefficient during the wet season.
· Gases produced during extended wastewater treatment operations can cause chronic health problems if not controlled.

Further Development of Technology: Expansion of experimental facilities to full-scale implementation is required. Dual distribution systems should be incorporated into new developments to make use of reclaimed wastewater.

Information Sources: Final Report of the Workshop on Alternative Technologies for Freshwater Augmentation in the Caribbean (Barbados, 24-27 October 1995), and Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru, 19-22 September 1995), OAS/UNEP.

Name of Technology: Raised Planting Beds and Waru-Waru Cultivation

4.1

Sector: Agriculture

Technology Type: Water Conservation

Technical Description: This technology is a combination of the rehabilitation of marginal soils, drainage improvement, increased water storage, more efficient use of radiant energy, and attenuation of the effects of frosts The technology consists of a system of embankments and channels The embankments serve as raised beds for cultivation, while the channels are used for water storage Water uptake in the raised beds is by diffusion and capillary movement of water from the channels There are three types of raised beds, the use of which is determined by the source of the water rain-driven systems, fluvial systems, and phreatic systems Design considerations include the depth of the water table, soil characteristics, and climatic conditions

Extent of Use: This technology has been used in the Lake Titcaca drainage basin in Peru and Bolivia for irrigation of potatoes and quinoa

Operation and Maintenance: Periodic reconstruction of the embankments is needed to repair eroded areas Cultivation in raised beds of different heights can mitigate erosion of soils during torrential downpours Animals should be excluded from cultivated areas Use of fungicides and insecticides may be required

Level of Involvement: This technology has been promoted, with technical assistance provided, by governmental agencies in Peru NGOs have also assisted in implementing this technology in Bolivia Farmers are responsible for the operation and maintenance of these systems

Costs: The cost of establishing this technology for the cultivation of potatoes in Peru was $14 60/ha cultivated Once established, the technology operates well for a period of three years, after which it should be reconstructed or extensively overhauled

Effectiveness of Technology: Preliminary results suggest an increase in crop production Effectiveness is affected by climatic conditions

Suitability: In areas with extreme climatic variation, ranging from droughts to floods, mountainous areas, and arid regions

Cultural Acceptability: This is an ancient and traditional technology, well accepted in the countries where it is used

Advantages:
· This technology mitigates the effects of extreme climatic variability
· It has a low cost
· It increases production of selected crops

Disadvantages:
· The technology has a relatively short lifespan before reconstruction is required
· Appropriate soil texture and composition are required
· It requires maintenance and period repair

Further Development of Technology: Despite its ancient heritage, this technology is experimental Application in other regions with different climatic and soil conditions should be evaluated

Information Sources: Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru, 19-22 September 1995), OAS/UNEP

Name of Technology: Small-Scale Clay Pot and Porous Capsule Irrigation

4.2

Sector: Agriculture

Technology Type: Water Conservation

Technical Description: This is a low-volume irrigation technology that uses clay pots or porous capsules, interconnected by plastic pipes, to deliver water to the soil. This ancient irrigation system has been modernized and applied in water-scarce areas. Clay pots are open at the top and are usually constructed from locally mined clay, or clay and sand, baked in home kilns or ovens. Capsules are closed and sometimes work under pressure, being regulated by a constant-level tank or reservoir. The number of pots or capsules required is a function of the volume of the container and the area of cultivation, soil conditions, and climatic conditions.

Extent of Use: This technology has been used in small-scale irrigation projects in arid and semi-arid areas of Argentina, Bolivia, Brazil, Ecuador, and Mexico. It is also used during drought periods in tropical countries including Guatemala, the Dominican Republic, and Panama.

Operation and Maintenance: Operation is simple, requiring only the opening and closing of valves to replace the water in the clay pots and porous capsules that has been used for irrigation. Installation requires care, especially in soil preparation. Hydrostatic pressures should be maintained at a constant level. Replacement of pots and capsules is required every 3 to 5 years. Maintenance includes checking for leaks when pressures cannot be maintained.

Level of Involvement: Community participation is essential to the implementation of this technology. Government institutions may participate in field testing of this procedure.

Costs: Costs vary according to the materials used and type of system employed. In Brazil, the cost of using clay pots was estimated at $1 300/ha, and of using porous capsules at $1 800/ha.

Effectiveness of Technology: Use of this technology has improved the stability of soils. Tests performed in Panama with the cultivation of fruit trees resulted in a yield of 6 fruits per plant or three times the yield obtained using conventional methods. In Bolivia, significant increases in the yield of potatoes were reported.

Suitability: In arid and semi-arid areas for small-scale agricultural applications, and in drought-prone areas.

Cultural Acceptability: This technology is gaining acceptance in agricultural communities in arid and semi-arid regions. It has been well accepted as a technology for use in household gardens.

Advantages:
· This technology has a low cost.
· It improves agricultural production.
· It reduces infiltration losses.
· It eliminates unwanted weeds.
· The systems are easy to operate and maintain.
· It can reduce the use of artificial fertilizers.
· It prevents soil erosion.
· It has minimal environmental impact.

Disadvantages:
· The technology is difficult to use in rocky soils.
· Broken pots or capsules can disrupt operation.
· Acquisition of pots or capsules may be difficult in certain areas.
· It is only applicable in small-scale applications.

Further Development of Technology: Improvements in the construction of the capsules by using a mixture of materials to increase or maintain porosity are proposed. Extension of the technology to larger-scale applications is required, as is educational programming to promote the use and benefits of the technology.

Information Sources: Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru, 19-22 September, 1995), OAS/UNEP.

Name of Technology: Automatic Surge Flow and Gravitational Tank Irrigation

4.3

Sector: Agricultural use

Technology Type: Water Conservation

Technical Description: This technology was developed to provide intermittent irrigation supplies for small-scale agriculture. The automatic surge flow irrigation system consists of a tank kept at a certain head and equipped with one or more siphons. Water for irrigation use is provided by siphoning water from the tank when required. The gravitational tank system is a similar system equipped with a discharge pipe, gate and float valve which allows the cyclical opening and closing of the gate. The design of these systems must consider irrigation water use, available hydraulic head, topography of the irrigated area, dimensions of the irrigated parcel, and soil characteristics.

Extent of Use: This technology has been used extensively for irrigation of small-scale plots of up to 4 ha in arid and semi-arid areas of Mexico.

Operation and Maintenance: These systems function automatically, using flow control devices, and need no external energy source. Maintenance is simple, requiring periodic cleaning of tanks, siphons, and discharge pipes.

Level of Involvement: The Mexican government, through educational institutions and small private agricultural enterprises, has promoted the use of this technology.

Costs: Capital costs of a surge flow automatic irrigation system capable of irrigating an area of 4 ha, manufactured in Mexico, was $600. The cost of a similar system using the graviational tank was $1400. The gravitational tank system has a longer life expectancy and greater efficiency of operation.

Effectiveness of Technology: Irrigation efficiencies of up to 75% have been achieved in the State of Zacatecas, Mexico. This is 50% higher than the irrigation efficiencies achieved with traditional systems. Savings in energy costs of up to 25% have also been reported.

Suitability: In arid and semi-arid areas with small storage areas and depleted aquifers.

Cultural Acceptability: It is well accepted in the areas of Mexico where it has been used and tested.

Advantages:
· This technology uses hydrologic energy as a driving force; it requires no external power source.
· It can use small wells, streams or reclaimed water as the water source.
· It has a low cost.
· Irrigation time and labor requirements are reduced.
· It is more efficient than traditional irrigation techniques.
· It is easy to operate and maintain.

Disadvantages:
· This technology is suitable for small-scale irrigation only.
· Significant preparation of the land is required; irrigated parcels should be levelled for best results.

Further Development of Technology: A fertilizer dispensing device is presently being developed as an additional element of the gravitational tank irrigation system. Informational programming on the utilization and efficiency of these systems is required.

Information Sources: Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru, 19-22 September, 1995), OAS/UNEP.

Name of Technology: Dual Water Distribution

4.4

Sector: Domestic water supply

Technology Type: Water Conservation

Technical Description: This technology involves the use of water supplies from two different sources, delivered to the user in two separate distribution systems. The supply of potable water is provided through one distribution system, and non-potable water through a separate system. The non-potable water is used for fire-fighting, sanitary flushing, and irrigation/watering. In most cases, the non-potable water source is either seawater or treated wastewater. The system requires a duplicate distribution system comprising pipes, pumping stations, and control valves. The piping is generally ductile or cast iron or fiberglass.

Extent of Use: The system is used in the Caribbean islands, on Saint Lucia and the U.S. Virgin Islands, to supply water for fire-fighting and street cleaning.

Operation and Maintenance: Problems have been experienced with this technology: valves have needed frequent servicing to remove fungal growths, pumps and motors consume much fuel and oil, and frequent testing of the systems is required to ensure efficient operation in the event of an emergency.

Level of Involvement: This technology is a government operation.

Costs: The cost of building a dual distribution system is almost exactly double that of building a single sourced system. The cost depends on the area served and the intended use of the system.

Effectiveness of Technology: This technology is highly efficient in supplying water for fire-fighting and street cleaning.

Suitability: In areas where a secondary source of water (usually seawater) is available and plentiful. Islands and coastal areas are best suited for implementation of this technology.

Cultural Acceptability: It is acceptable as an alternative source of supply for non-potable use; however, concerns about possible human health impacts due to cross-contamination of supplies remain.

Advantages:
· It allows use of secondary water supplies, unsuited to potable use, for non-potable purposes.
· The volumes of water and wastewater requiring treatment are reduced.
· This technology leaves more potable water available for domestic consumption.

Disadvantages:
· The cost of this technology can be twice that of a single-sourced distribution network.
· The public health risk due to cross-contamination of supplies is increased.
· Seawater sources are highly corrosive and can increase maintenance requirements and costs.
· Maintenance is more difficult and costly due to the greater number of pumps, pipes and valves, and the need to prevent cross-contamination.
· Should seawater-based effluents be returned to a wastewater treatment facility, the efficiency of the plant may decline.

Further Development of Technology: Development of corrosion-resistant pipes, pumps and valves, and the use of fiberglass as a substitute for iron piping, would increase the use of this technology; use of PVC pipes, values and fittings would reduce maintenance requirements; and reduced costs of materials for a dual distribution system would encourage more widespread use of this technology by making it more cost-effective.

Information Sources: Final Report of the Workshop on Alternative Technologies for Freshwater Augmentation in the Caribbean (Barbados, 24-27 October, 1995) and Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru, 19-22 September, 1995), OAS/UNEP.

Name of Technology: Other Water Conservation Practices

4.5

Sector: Domestic water supply; agriculture; industry and business

Technology Type: Water Conservation

Technical Description: Water conservation practices vary depending on the use. Residential users can conserve water by using low-flow plumbing fixtures, sometimes provided at reduced prices by water utilities through retrofit programs. The most common domestic low-flow devices are low-flush toilets, low-flow showerheads, pressure reduction valves, tap aerators, and the reuse of grey water in household gardens. Landscape water conservation practices include the use of low-volume sprinkler systems and xeriscaping. Agricultural water conservation practices include soil compaction and levelling, diking to prevent runoff, and selection of irrigation rates and schedules to minimize evaporative losses. Industrial and commercial water conservation practices include water recycling, particularly in cooling systems and washing of equipment. Regional water supply companies and water utilities can encourage water conservation by programs of leak detection and repair, programs of distribution network maintenance and rehabilitation, metering and pricing policies, well-capping, retrofit programs, drought management planning, and public awareness programming, focussing on demand and supply management by their customers/users.

Extent of Use: Most of the conservation measures have been used in the U.S.A., particularly in water-stressed states such as Arizona, California and Florida. Some Latin American countries, including Brazil, Chile, and Mexico, have used water recycling. Chile has encouraged the development of a water market which has resulted in a shift toward less water-intensive agricultural practices.

Operation and Maintenance: Low-flow water conservation devices require maintenance and repair. Leak detection equipment and meters require periodic calibration and maintenance.

Level of Involvement: Installation and maintenance of low-flow household devices may require government incentives to promote acceptability to the consumer. Government regulations and incentives are necessary in order to implement most water conservation measures. Agricultural extension efforts may be needed to encourage outdoor water conservation practices such as irrigating in the early morning or late afternoon to minimize evaporative losses. Community participation, especially in voluntary conservation of water, is a necessary prerequisite for a successful water conservation program.

Costs: The cost of low-flow devices is usually higher than that of conventional fixtures, although long-term savings usually more than compensate for the added cost. Significant savings have been reported by industrial users adopting water recycling systems.

Effectiveness of Technology: Water savings of 20% to 80% have been documented. A reduction in water pressure of 50% can result in a water saving of about 33% of the preexisting use. Early morning or late afternoon irrigation can result in measurable water savings. The conversion to a recycling cooling system in an industrial plant in the state of California, U.S.A., resulted in an estimated water saving of 20 000 to 28 000 l/day.

Suitability: In all areas, but particularly in high water-use sectors, such as industries and agricultural operations, in drought-prone areas. The technology is well suited to individual water users in developing countries.

Cultural Acceptability: Most water conservation measures have been implemented as a result of government regulation. Nevertheless, most practices have been well-accepted, especially by users who realize an economic benefit, although industrial, agricultural, and commercial users have been more receptive to these benefits than domestic users.

Advantages:
· Low-flow devices produce significant water savings over conventional fixtures.
· Water recycling significantly reduces industrial water use.
· Leak detection and metering can reduce water use by 30% to 50%.
· Metering introduces accountability for water use.
· Pricing schemes provide economic incentives for water conservation.

Disadvantages:
· Initial cost of low-flow devices is higher than for conventional fixtures.
· Use of treated wastewater for irrigation poses some degree of health risk.
· Modification of manufacturing processes and/or changes to plumbing/piping can make recycling costly to implement.
· Implementation of leak detection and metering systems is costly and will affect the price of water in the short term.

Further Development of Technology: Low-flow plumbing devices need to be made more cost-effective; improvements in equipment used in leak detection and metering are needed to increase durability and efficiency; and widespread implementation of public awareness programs to encourage water conservation, and focussing particularly on its economic and environmental benefits, is needed.

Information Sources: Informe Final del Seminario-Taller sobre Tecnolog Alternativas para Aumentar la Disponibilidad de Agua en Amca Latina (Lima, Peru. 19-22 September, 1995), OAS/UNEP, and USEPA, "Cleaner Water Through Conservation," Washington, D.C., 1995 (Report 841/8-95-002).