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Towards an ecological approach to sanitation This article was prepared by Uno Winblad, Director of a SANRES, an international research project which is seeking environmentally sound and sustainable sanitation options, especially for the urban poor. It was delivered as a speech at the International Toilet Symposium, Toyama, Japan, October 1996. It is included in the Kit to offer new ideas and stimulate discussion and debate concerning sanitation systems of the future. Introduction 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, according to WHO estimates nearly 3 000 million, lack even the most basic sanitation (WHO 1996). In my speech today I shall discuss the theme of the Symposium, "the environment and toilets", in this global perspective. My conclusion is that we need a paradigm shift - a shift away from the present non-ecological, "flush-and-discharge" approach, to a holistic approach, taking account of the fact that sanitation is a system where the environment is an important component. What we need is ecological sanitation and to get that we must have ecological toilets. In this paper I shall present a tentative list of criteria for ecological sanitation systems. In the second half of my presentation I shall show examples of ecological toilets from around the world. The basic message of my presentation is: Don’t mix! Definition I prefer to talk about "sanitation" rather than "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: 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 It is no exaggeration to state that sanitation is a problem that in many places around the world has reached crisis proportions (Black 1994). The main reasons behind this global sanitation crisis are rapid population growth and an unsuitable technological response. Rapid population growth The rapid population growth results in ever increasing densities, in urban growth, in the establishment of squatter areas and in a high burden of disease. 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 1 000 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. Urban growth. Today 2 500 million people live in urban areas. Thirty years from now the urban population will reach 5 000 million. 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. 20–30 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, 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 1 000 live births in one year) are far higher in the poor sections of many cities than in better-off sections. The examples in the table below show that the Infant Mortality Rate in poor areas is 3–10 times higher than in the non-poor areas (EHP 1996). 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. 1 500 million people are currently infected with intestinal worms, all of which are spread through human excreta (WHO 1995). 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 towns around the world, even in poor countries where people cannot afford it and in arid areas where there is hardly enough water for drinking. This glorification of flush-and-discharge is based on a number of assumptions:
However, none of these assumptions is correct:
Let me elaborate on each of these points:
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. 50 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 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 they contain a bacterium, Micrococcus ureae, which when mixed with urine produces very bad smell (Wolgast 1993). Water scarcity. A flush system does not work without water. To flush away our 550 litres in a sewered toilet each of us is using something like 15 000 litres of pure water every year. Most cities in the world don’t have enough water to provide anything like 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 (UN Habitat 1996). Chronic fresh water 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 (UNDP 1996). Wastewater treatment. 95 per cent of all sewage in the Third World is discharged completely untreated into surface waters (World Resources Institute 1992). 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 phosphorous and nitrogen. 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 be decomposed and 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". 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 for 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 (Stenström 1996). Drop-and-store systems resulting in large numbers 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 fundamental rethinking of the problem. 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:
Don't mix:
Urine, if we don’t want to use it, can be infiltrated or evaporated. Better still is to reuse it because urine 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. Faeces can, if necessary, be processed in several steps before they are reused. 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 treatment taking place on site, usually through dehydration or decomposition. Where intestinal parasites are common, some form of secondary treatment may be required, for example high temperature composting. Tertiary treatment by for example incineration 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. We save a lot of water, we save on pipe networks and treatment plants, we create employment and we preserve the environment. By not mixing greywater and blackwater we can use a number of relatively simple on-site treatment methods for the wastewater generated by food preparation and washing. By not mixing stormwater and wastewater we can, with relatively simple methods, store, treat and recycle stormwater locally (Niemczynowicz 1994). Industrial wastewater containing dangerous, poisonous chemicals must of course be taken care of at the source, by the industry where it is generated. 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. It is not a technical question because it can be done, nor an economic one because prevention is bound to cost less than treatment. The question is political. Examples of ecological sanitation "Don't mix" is central to the new paradigm and to the concept of ecological sanitation. I shall now go through a number of concrete examples, some old, some new, from various parts of the world. First a few words about the technicalities of keeping urine and faeces apart. The most straightforward methods is of course 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. The first example is from Yemen: 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 hole 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. 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. (Winblad and Kilama 1985.) The second example is from Vietnam and Guatemala. It is a two-chamber dehydrating toilet with urine separation. The toilet chambers are built above ground. Urine is collected and piped into a container or a 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. 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. In a further development of the LASF toilet it 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 Técpan near San Salvador. A prefabricated version of the solar-heated toilet has been produced in Mexico for more than 15 years. 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. Here is one example ("WM Ekologen" system) based on urine separation and dehydration. 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 one, the Clivus Multrum, 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 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. The failure of conventional sanitation technologies to prevent pollution is of particular concern in small islands. Nearly every Pacific island nation has identified critical environmental problems resulting from conventional disposal methods. The CCD toilet in Kiribati was developed by Greenpeace in an attempt to achieve zero-discharge. 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. (Rapaport 1995). Finally an example from Ecuador, high up the Andes mountains: a two-chamber, solar-heated composting toilet (Dudley 1993). At this altitude there is no need for urine separation. The natural evaporation takes care of any excess liquid. Although called a "composting toilet" it is more likely to function as a dehydration toilet. These examples from around the world show that ecological sanitation exists, that it works and is feasible. Conclusions In this presentation I have raised a number of issues related to the environment and toilets. My conclusions are short and simple: Don’t mix! Don’t flush! Don’t waste!
For the future of our cities ecological sanitation is not only an option, it is a necessity! Updated 03/03/03 |
