Ecological Sanitation Closing the Loop 35

oday, nearly half of humanity has no access to any type of sanitation (WHO and UNICEF 2000). The rest of humanity relies on conventional approaches to sanitation, which fall into one of two categories: water-borne systems and pit latrines. Both 'flush and discharge' and ' drop and store' technologies were built on the premise that the nutrients we excrete have little value, and that waste is suitable only for disposal. Consequently, the environment is polluted, nutrients are lost, and a wide array of health problems result (Esrey 2000). Ecological sanitation (Esrey 1998) represents a shift in the way people think about and act upon human excreta. It is an ecosystem approach (Figure 1) that recognis-es the need and benefit of promoting human health and well-being, while at the same time recovering and recycling nutrients, and conserving and protecting water sources. It represents a closed-loop approach, and is an attempt to move away from linear solutions of waste disposal towards a circular flow of nutrients. DESIGN FEATURES Conventional sanitation solutions assume that the environment can handle the waste, or they shift the burden to downstream communities. Ecological sanitation, on the other hand, minimises the reliance on external inputs, while simultaneously reducing the output of wastes from the system. There are two basic design features of ecological sanitation. One is urine-diversion, in which urine and faeces are never mixed (see figure 2). The pedestal has a dividing wall, in which the urine exits from the front of the toilet, and faeces drop below the toilet from the back of the bowl. Another design combines urine and faeces, at which point urine and faeces can be processed together or sepe-rated. In either case, it is possible to manage urine, faeces or excreta with little or no water, and it is also possible to keep the end-product out of ground and surface waters. Pathogens are treated close to the point of excretion. Nearly all pathogens in excreta are found in faeces, while urine is sterile with few exceptions (e.g. Schistosoma haemotobium-a trematode worm which causes Bilharzia or Schisto-somiasis). If faeces are kept separate from urine, the pathogens in faeces are much more easily treated in an ecological toilet without the use of harmful chemicals or complex processes and treatment plants. Microbiological testing on urine diversion toilets is being done in a number of countries. Evidence to date (Stenström 1999) indicates that the addition of …