Towards an ecological approach to sanitation - Uno Winblad1

¹ WKAB, Pataholm 5503, 5-384 92 ALEM, Sweden. The views expressed in this article are controversial and not necessarily shared by all members of the Working Group on Promotion of Sanitation or the World Health Organization. However, the author's viewpoint stimulates thinking and debate in the sector and may encourage further research, development and field trials of alternative sanitation systems. Some of the alternative systems are featured in other articles in this book.

Many of us have a bathroom; we turn a tap and get water, we flush the toilet and get rid of whatever we have put there. We take these facilities for granted. But most people in the world have no piped water in the house and many (WHO estimates nearly 3000 million) lack even the most basic sanitation (1).

There is a need for a paradigm shift away from the present non-ecological, “flush-and-discharge” approach, to a holistic approach, taking into account that sanitation is a system where the environment is an important component. To meet the requirement for ecological sanitation we must have ecological toilets. This article presents a tentative list of criteria for ecological sanitation systems and gives examples of ecological toilets from around the world. The basic theme of this article is: Don't mix!

Definition

“Sanitation” is a better term that “toilets”. A flush toilet is basically a machine for mixing human urine, faeces and water. Sanitation, on the other hand, is a system. The main components of that system are nature, society, process and device (Figure 1).

When discussing sanitation, and particularly sanitation in relation to the environment, we have to consider all these components. We cannot afford to neglect any one of them.

The crisis in sanitation

Sanitation is a problem that in many places around the world has reached crisis proportions (2). The main reasons behind this global sanitation crisis are rapid population growth and an unsuitable technological response.

Rapid population growth

Rapid human population growth results in ever increasing densities, in urban growth, in the establishment of squatter areas and in a high burden of disease.

Figure 1. The main components of a sanitation system

Figure 2. Human population density changes over the last 10 000 years; 1 dot = 5 million people (3).

Densities. There was a time in history when sanitation was less of a problem - or no problem at all: the human population was small and dispersed over a large area.

But the situation is changing rapidly. The human population is now 1000 times greater than it was 10 000 years ago. Over the past 30 years it has doubled and it may double again in the next 40-50 years. One consequence of this population growth is that we now live closer together, at ever increasing densities, putting higher and higher pressure on the environment. The closer together we live, the more important it is for us to have access to, and make use of, good sanitary facilities (Figure 2).

Urban growth. Today 2500 million people live in urban areas. Thirty years from now the urban population will reach 5000 million (Figure 3).

Figure 3. Urban population 1995-2025, less developed and more developed countries (4).

Squatter areas. If present trends continue the majority of urban dwellers in the world will live in unplanned, unserviced squatter areas in small and medium-sized towns. The typical urban dweller of the next century is not going to live in a pleasant, comfortable flat or house, with paved streets, electricity, a sufficient, pure and reliable supply of water, flush toilet, garbage collection and everything else that we tend to take for granted. Twenty to thirty years into the next century the typical urban dweller is more likely to live in a health-threatening environment: in a temporary shack along a filthy unpaved lane, water collected from a communal tap with erratic supply or bought from a water vendor, no toilet, and no garbage collection.

Disease burden. There is a marked difference in health between those who live in poor and in non-poor areas as reflected in the respective infant mortality rates. Infant mortality rates (meaning number of infant deaths per 1000 live births in one year) are far higher in the poor sections of many cities than in better-off sections. The examples in Table 1 show that the infant mortality rate in poor areas is 3-10 times higher than in the non-poor areas (5).

Table 1. The effect of poverty on the infant mortality rate

City	Poor	Non-poor
Manila, Philippines	210	76
SPaulo, Brazil	175	42
Guatemala	113	33
Karachi, Pakistan	152	32
Delhi, India	180	18

Poor environmental conditions give rise to high rates of diarrhoeal diseases, to helminth infections like ascariasis and hookworm, and to vector-borne diseases like malaria, dengue fever and Japanese encephalitis. More than three million people die of diarrhoea every year, most of them infants and young children; 1500 million people are currently infected with intestinal worms, all of which are spread through human excreta (6).

Unsuitable technological response

Conventional sanitation based on flush toilets, sewers and central treatment plants cannot solve these problems. Nor can they, in high-density urban areas, be solved by systems based on pit latrines of different kinds.

Flush-and-discharge. Flush-and-discharge systems make the problems of sanitation much worse. Under these systems a relatively small amount of dangerous material - human faeces - is allowed to pollute a huge amount of water. In spite of this, flush-and discharge is universally regarded as the ideal option for urban areas. Almost without question it is promoted in cities and town around the world, even in poor countries where people cannot afford it and in arid areas where there is hardly enough water for drinking (Figure 4).

Figure 4. Flush-and-discharge

This glorification of flush-and-discharge is based on a number of assumptions:

- that the problem is one of “sewage disposal”;
- that fresh water is an unlimited resource;
- that at the end of the pipe the sewage is treated; and
- that the environment can take care of the discharge from the treatment plant.

However, none of these assumptions is correct;

- the basic problem is the disposal of human faeces and urine, not “sewage”;

- outright shortage of water is, or will very soon become, a major problem for most Third World cities;

- only a tiny fraction of all sewage produced in the Third World is treated; and

- all over the world we can find examples of natural ecosystems destroyed by the discharge of untreated or partly treated sewage.

Each of these points is discussed in more detail below.

Sewage disposal vs. management of urine and faeces. A human body does not produce “sewage”. Sewage is the product of a particular technology. The human body produces urine and faeces. These are often referred to as “human excreta” but it is important to remember that they are in fact two different substances which leave the body through separate openings and in different directions.

Each person produces about 500 litres of urine and 50 litres of faeces per year. Fifty litres of faeces should not be too difficult to manage. It is not a very pleasant product and may contain pathogenic organisms. But the volume is small: when dehydrated it is actually no more than a bucketful per person per year. The real problem is that in the flush-and-discharge system faeces are not handled on their own. They are mixed with urine. This means that instead of 50 litres of a heavily polluted substance we have to take care of 550 polluted, dangerous and extremely unpleasant litres.

One of the reasons behind the unpleasantness of the mixture of urine and faeces is that faeces contain a bacterium, Micrococcus ureae, which when mixed with urine produces a very unpleasant smell (7).

Water scarcity. A flush system does not work without water. To flush away the 550 litres of faeces and urine in a sewered toilet each person uses about 15 000 litres of pure water every year. In most cities in the world there is nowhere near enough water to provide that amount for each of its inhabitants. The typical Third World city solves this problem by providing flush-and-discharge only to the rich, which of course means that there is even less water available to the poor.

Globally, some 80 countries with 40 per cent of the world's population are already suffering from water shortages at some time during the year (8). Chronic freshwater shortages are expected by the end of the decade in much of Africa, the Middle East, northern China, parts of India and Mexico, the western United States, northeastern Brazil and in the former Soviet Central Asian republics. China alone has 300 cities facing serious water shortages (9).

Wastewater treatment. Ninety-five per cent of all sewage in the Third World is discharged completely untreated into surface waters (10). Many cities do not have any sewage treatment system at all, and of those that do, most serve only a small fraction of the population.

Even where there is treatment, the vast majority of sewage treatment technologies in use today still contribute significant amounts of pollutants to the environment. Even modern treatment facilities cannot cope with for example phosphates and nitrates. Nor are treatment plants designed to detoxify chemical wastes. Primary treatment simply filters out floating and suspended material; secondary treatment facilitates the biological degradation of faeces and urine and other similar material; and disinfection destroys infectious organisms. Most of the industrial and household toxic wastes released into sewers are either discharged into receiving waters, or remain in the sludge.

Ecosystem overload. In the past it was a common assumption that the pollution which results from conventional sanitation technologies can be safely assimilated by the environment. This assumption is not correct. Some chemicals will decompose and be removed by natural processes, but most will remain in the environment. The inevitable end products of a sewage system are polluted waters and toxic sludge.

The four conventional sludge disposal methods are ocean dumping, landfilling, incineration and application on agricultural land. From an environmental point of view all these methods are unacceptable and from all over the world we have reports of the degradation of the environment due to sewage discharge and sludge disposal.

Drop-and-store. The alternative to flush-and-discharge is “drop-and-store” (Figure 5).

Such systems can be simple and relatively low-cost, and they are easy to understand and to operate. But they have many drawbacks: smell, fly breeding, risk of pit collapse, and often a relatively short life. From time to time new pits have to be dug. This may be difficult on crowded sites. In many cases drop-and-store systems cannot be used at all: on rocky ground, where the groundwater table is high and in areas periodically flooded. Recent experiments using biotracers indicate that the risk of groundwater contamination from pit latrines is greater than generally assumed (11).

Figure 5. Drop-and-store

Drop-and-store systems resulting in large number of excreta-filled pits are not feasible in densely built up urban areas. Nor is the Japanese jokaso system (“jokaso” is a Japanese technology for collection and treatment of nightsoil) a realistic option for poor countries. With manual collection the jokaso system is unacceptable for health reasons. With collection by vacuum pump truck, as in Japan, the system is extremely expensive in terms of initial investment, operation and maintenance.

A new approach

Conventional sanitation in the form of flush-and-discharge offers no solution to the global sanitation crisis. We need a new approach, a new paradigm in sanitation.

The major question in sanitation today is: How can a rapidly growing city short of money and water and with limited institutional capabilities achieve safe, non-polluting sanitation for all its inhabitants?

A new approach to sanitation must be based on equity, prevention and sustainability. Sanitation systems of the future should:

- ensure equity in the distribution of water;
- prevent harm to human health;
- achieve zero pollution discharge;
- enable us to recycle human urine and faeces as plant nutrients;
- adjust to small municipal budgets and low-income households; and
- offer a level of convenience comparable to that of conventional options.

We can call this new paradigm ecological sanitation. The first principle of ecological sanitation is: Don't mix!

Don't mix:

- human urine and faeces;
- human excreta and water;
- blackwater and greywater;
- household wastes and industrial wastes; or
- wastewater and rainwater.

By keeping urine and faeces apart, problems of bad odours and fly-breeding are reduced or even eliminated, and storage, treatment and transport are made easier.

If urine is not going to be used, it can be soaked into the ground or evaporated. However it is better to recycle urine because it contains nitrogen and phosphates in forms that are easily absorbed by plants. Urine, diluted with water, can be used directly in the garden or it can be stored and used at a later date (Figure 6).

Figure 6. Alternatives for managing urine

Faeces can, if necessary, be processed in several steps before they are reused (Figure 7).

In an ecological toilet, that is a dry toilet with urine separation, they are subject to primary treatment, basically dehydration, which also effectively destroys most of the pathogenic organisms. If this local primary treatment is insufficient, the dry output from the toilet can be transported to a neighbourhood composting station for secondary treatment. If a sterile product is required a tertiary treatment could be incineration.

The amount of treatment required depends on the health status of the users as well as on the intended end use of the product. Most pathogenic organisms can be destroyed by the primary on-site treatment which is usually dehydration or decomposition. Where intestinal parasites are common, some form of secondary treatment may be required, for example high-temperature composting. Tertiary treatment by incineration, for example, should not be necessary but remains an option in exceptional circumstances.

By not mixing human excreta and flushing water the sanitation problem is limited to managing a comparatively small volume of urine and faeces. As a result, a lot of water can be saved, expenditure on pipe networks and treatment plants is reduced, jobs are created and the environment is preserved.

By not mixing greywater and blackwater a number of relatively simple on-site treatment methods can be used for the wastewater generated by food preparation and washing.

By not mixing stormwater and wastewater relatively simple methods can be used to store, treat and recycle stormwater locally (12).

Industrial wastewater containing dangerous, poisonous chemicals must of course be taken care of at source, by the industry generating it. All the heavy metals and toxic chemicals used in industrial processes must be retained in closed loops. This can be accomplished by the introduction of the polluter-pays principle. Such a change is economically and technically feasible but in many places politically difficult.

Figure 7. Treatment of faeces in stages

Examples of ecological sanitation

“Don't mix” is central to the new paradigm and to the concept of ecological sanitation.

There are three methods by which urine and faeces can be kept apart (Figure 8). The most straightforward method is never to mix the two. This way the urine remains relatively sterile and can be reused without any further treatment. Another possibility is to mix and then drain. The third possibility is to mix and then evaporate. These different methods are illustrated in the examples of ecological sanitation, some old, some new, described below.

The first example is from Sanaa in Yemen (Figure 9): a one-chamber dehydrating toilet with urine separation placed in a bathroom several floors above street level. In a traditional Yemeni town house the upper floors have toilet-bathrooms next to a vertical shaft that runs from the top of the house down to the level of the street. The faeces drop through a hold in the squatting slab. The urine drains away through an opening in the wall of the house, down a vertical drainage surface on the outer face of the building. Anal cleaning with water takes place on a pair of stones next to the squatting slab.

Figure 8a. Ways of separating urine and faeces - keep separate

Figure 8b. Ways of separating urine and faeces - mix then drain

Figure 8c. Ways of separating urine and faeces - mix then evaporate

The water is drained away the same way as the urine. As Sanaa has a hot, dry climate the faeces quickly dry out. They are collected periodically and used as fuel (13).

The second example is from Vietnam and Guatemala. It is a two-chamber dehydrating toilet with urine separation (Figure 10). The toilet chambers are built above ground. Urine is collected and piped into a container or soakpit. Faeces are dropped into one of the chambers, the other one is kept closed. Papers used for anal cleaning are put in a metal bucket and burnt.

Each time they defecate, people sprinkle some ashes, lime or soil on the faeces. When the chamber is nearly full it is topped up with soil and the drop hole is sealed with mud. (In Guatemala a plastic bag is placed over the seat.) The second chamber is then used. When that one is nearly full, the first chamber is opened and emptied. The dehydrated faecal material is used as a fertilizer and soil conditioner.

Figure 9. Section through a house in the old part of the town of Sanaa. On the upper floors there are bathrooms with urine-separating toilets

Figure 10. The Vietnamese double-vault, dehydrating toilet, here shown without superstructure. The LASF toilet in Guatemala is of similar design although provided with two seat-risers rather than a squatting slab with two holes

This type of latrine is also used in high-density urban squatter areas, for instance in Hermosa Provincia, in the centre of San Salvador, the capital of El Salvador (Figure 11).

In a further development of the LASF toilet is has been equipped with a solar heater. The main purpose of the heater is to increase evaporation from the chamber. The example below is from the community of Tan near San Salvador (Figure 12).

Figure 11. LASF toilets in a densely-populated squatter area in central San Salvador

Figure 12. A dehydrating toilet with urine separation and solar-heated vault. El Salvador

Figure 13. A composting toilet with solar heating but no urine separation, Mexico

A prefabricated version of the solar-heated toilet has been produced in Mexico for more than 15 years (Figure 13). It can be used either as a dehydrating toilet or as a composting toilet; there are versions with and without urine separation and with one or with two chambers.

Ecological sanitation is not only for poor countries. In Sweden a number of ecological toilets have been on the market for many years. One type, “WM Ekologen” system, is based on urine separation and dehydration (Figure 14). Urine is stored in an underground tank until reused as a fertilizer. Faeces are dehydrated in a bucket directly under the toilet seat. The toilet is placed indoors. The system is usually combined with separate, on-site treatment of greywater.

Another example, the Clivus Multrum (Figure 15), has no urine separation and is based on decomposition of faeces and organic household wastes. Urine and faeces are mixed with organic household refuse, in this case via a refuse chute from the kitchen. The chamber is placed in the basement, directly under the bathroom and kitchen. This system is by now well tested in Scandinavia as well as in North America and has actually been on the market for nearly 50 years.

Figure 14. A dehydrating toilet with urine separation, Sweden

The failure of conventional sanitation technologies to prevent pollution is of particular concern on small islands. Nearly every Pacific island nation has identified critical environmental problems resulting from conventional disposal methods. The CCD toilet in Yap was developed by Greenpeace in an attempt to achieve zero-discharge (Figure 16). It is a single-chamber composting toilet combined with a greenhouse for evapo-transpiration of urine and water. A nylon fishing net, hanging from hooks imbedded in the chamber walls, is used to separate solids from liquids. A mat woven from palm leaves sits in the net to catch solid materials deposited through the toilet seat. In some units, strips of polyester from old clothing hang from the net to enhance evaporation by acting as wicks to draw up liquids into the airflow generated by the large diameter vent pipe (14).

Figure 15. A composting toilet without urine separation, Sweden

Figure 16. The CCD composting toilet with evapo-transpiration, Yap

The final example is a two-chamber, solar-heated composting toilet from Ecuador, high up the Andes mountains (Figure 17) (15). At this altitude there is no need for urine separation as natural evaporation takes care of any excess liquid. Although called a “composting toilet” it is more likely to function as a dehydration toilet.

Figure 17. A solar-heated dehydrating toilet developed by FUNHABIT in Ecuador

These examples from around the world show that ecological sanitation exists, that it works and is feasible.

Conclusions

This article has raised a number of issues related to the environment and toilets. The conclusions are short and simple: Don't mix! Don't flush! Don't waste!

· Don't mix urine and faeces - keep separate!
· Don't flush away faeces - dehydrate!
· Don't waste a valuable resource - fertilize!

Ecological sanitation is not merely an option for the future of our cities - it is a necessity!

References

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(2) Black M. Mega-slums: the coming sanitary crisis. London, WaterAid, 1994.

(3) Boyden S, Dover S. Natural-resource consumption and its environmental impacts in the western world - impacts of increasing per capita consumption. Ambio, 1992, 21(1):63-69.

(4) UN. World urbanization prospects 1994. New York, United Nations, 1995.

(5) EHP (Environmental Health Project) Health and the environment in urban poor areas - avoiding a crisis through prevention. In: Capsule Report, No 1, March 1996. Cambridge, Massachusetts, USA, 1996.

(6) WHO. Community water supply and sanitation: needs, challenges and health objectives. Report of the Director General. Forty-eighth World Health Assembly, Provisional agenda item 32.1, Geneva, World Health Organization, 1995 (unpublished document A48/INF.DOC/2).

(7) Wolgast M. Rena vatten - om tankar i kretslopp. Uppsala, Creanom HB, 1993 (in Swedish).

(8) UN Habitat. Water crisis to strike most developing world cities by 2010. UN Habitat press release, Nairobi, 1996.

(9) UNDP. Habitat II, Dialogue III: Water for thirsty cities, Report of the Dialogue. United Nations Development Programme, United Nations Conference on Human Settlements, June 1996, Istanbul.

(10) WRI. World resources, 1992-1993. New York, Oxford University Press, 1992.

(11) StenstrA. Water microbiology for the 21st century. Paper presented at workshop 3, Stockholm Water Symposium, 7 August 1996, Stockholm.

(12) Niemczynowicz J. New aspects of urban drainage and pollution reduction towards sustainability. Water Science and Technology, 1994, 30(5).

(13) Winblad U, Kilama W. Sanitation without water. London, Macmillan, 1985.

(14) Rapaport D. Sewage pollution in Pacific island countries and how to prevent it. Eugene, Oregon, Centre for Clean Development, 1995.

(15) Dudley E. The critical villager - beyond community participation. London, Routledge, 1993.

© Uno Winblad, 1996, edited by WHO with permission of Uno Winblad, 1997.