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Ecological sanitation, also known as ecosan or eco-san, is a sanitation process that uses human black-water and sometimes immediately eliminates faecal pathogens from any still present wastewater (urine) at the source. The objectives are to offer economically and ecologically sustainable and culturally acceptable systems that aim to close the natural nutrient and water cycle.
Ecological sanitation (ecosan) offers a new philosophy of dealing with what is presently regarded as waste and wastewater. Ecosan is based on the systematic implementation of reuse and recycling of nutrients and water as a hygienically safe, closed-loop and holistic alternative to conventional sanitation solutions. Ecosan systems enable the recovery of nutrients from human faeces and urine for the benefit of agriculture,thus helping to preserve soil fertility, assure food security for future generations, minimise water pollution and recover bioenergy. They ensure that water is used economically and is recycled in a safe way to the greatest possible extent for purposes such as irrigation or groundwater recharge.
To reduce the health risks related to sanitation, contaminated water and waste.
To prevent the pollution of surface and ground water.
To prevent the degradation of soil fertility.
To optimise the management of nutrients and water resources.
In a very broad sense the recovery and use of urine and faeces has been practised over millennia by almost all cultures. The uses were not limited to agricultural production (although for modern application this maybe of most relevance), like the Romans who were well aware of the disinfecting attributes of urine and also used it for washing clothing.
The most widely known example of the diligent collection and use of human excreta in agriculture is China. Reportedly, the Chinese were aware of the benefits of using excreta in crop production before 500 B.C., enabling them to sustain more people at a higher density than any other system of agriculture. The value of “night soil” as a fertiliser was clearly recognised with well developed systems in place to enable the collection of excreta from cities and its transportation to fields. Elaborate systems were developed in urban centres of Yemen enabling the separation of urine and excreta even in multi-story buildings. Faeces were collected from toilets via vertical drop shafts, while urine did not enter the shaft but passed instead along a channel leading through the wall to the outside where it evaporated. Here, faeces were not used in agriculture but were dried and burnt as fuel.
In Mexico and Peru, both the Aztec and Inca cultures collected human excreta for agricultural use. In Peru the Incas had a high regard for excreta as a fertiliser, which was stored, dried and pulverised to be utilised when planting maize.
In the Middle Ages, the use of excreta and grey-water was the norm. European cities were rapidly urbanising and sanitation was becoming an increasingly serious problem, whilst at the same time the cities themselves were becoming an increasingly important source of agricultural nutrients. The practice of using the nutrients in excreta and wastewater for agriculture therefore continued in Europe into the middle of the 19th Century. Farmers, recognising the value of excreta, were eager to get these fertilisers to increase production and urban sanitation benefited.
The increasing number of research and demonstration projects for excreta reuse carried out in Sweden from the 1980s to the early 21st century aimed at developing hygienically safe closed loop sanitation systems. Similar lines of research began elsewhere, for example in Zimbabwe, in the Netherlands, Norway and Germany. These closed-loop sanitation systems became popular under the name “ecosan”, “dewats”,“desar”, and other abbreviations. They placed their emphasis on the hygenisation of the contaminated flow streams, and shifted the concept from waste disposal to resource conservation and safe reuse.
Ecological sanitation (Ecosan) is a new holistic paradigm in sanitation, which is based on an overall view of material flows as part of an ecologically and economically sustainable wastewater management system tailored to the needs of the users and to the respective local conditions. It does not favour a specific sanitation technology, but is rather a new philosophy in handling substances that have so far been seen simply as wastewater and water-carried waste for disposal.
Prevents disease and promotes health.
Protects the environment and conserves water.
Recovers and recycles nutrients and organic matter.
Ecosan offers a flexible framework, where centralised elements can be combined with decentralised ones, waterborne with dry sanitation, high-tech with low-tech, etc. By considering a much larger range of options, optimal and economic solutions can be developed for each particular situation.
Thus, the most important advantages of ecological sanitation systems are:
Improvement of health by minimising the introduction of pathogens from human excreta into the water cycle.
Promotion of safe, hygienic recovery and use of nutrients, organics, trace elements, water and energy.
Preservation of soil fertility.
Contribution to the conservation of resources through lower water consumption, substitution of mineral fertiliser and minimisation of water pollution.
Improvement of agricultural productivity and food security.
Preference for modular, decentralised partial-flow systems for more appropriate cost-efficient solutions adapted to the local situation.
Promotion of a holistic, interdisciplinary approach.
Material flow cycle instead of disposal of valuable resources.
Guangxi province, China - large-scale project of urine diverting dehydration toilets. The dissemination programme of ecological dry toilets for Hsinchu County, Guangxi province, one of the poorest provinces in China, started in 1997 with support of UNICEF, SIDA and the Red Cross and has been expanded to 17 provinces until the year 2003. By this year, the scale of the project had increased to approximately 685,000 toilet units – today more than one million double vault urine diversion dehydration toilets (UDDTs) are installed in rural areas of China.
In UDDTs, urine and faeces are collected separately: The urine is collected in the front and lead by a plastic pipe to a storage canister from where it can be used as a fertiliser in agriculture, the faeces fall at the back in one of two ventilated storage chambers and are covered with ash for better dehydration. After about one year of storage the dried material can be removed and used as a soil conditioner in agriculture.
KfW, Frankfurt, Germany - vacuum toilets + grey-water treatment The sanitation concept of the modern office building “Ostarkarde” of the KfW Bankengruppe in Frankfurt is based on a separate excreta and grey-water collection. While urine and faeces are collected via vacuum toilets and a vacuum sewerage using much less water for flushing, the grey-water from hand washing and kitchen is collected and treated separately in a compact activated sludge reactor combined with membrane filtration. The treated grey-water is then reused for toilet flushing and cleaning water. The amount of grey-water can be reduced by 76% by this cost-efficient system which could be one of the prior choices for sanitation systems of newly constructed office buildings.
Tanum Municipality in Sweden has introduced urine separation toilets to recover phosphorus.
Often, water used in flush toilets is of drinking quality. Only 1% of global water is drinkable, therefore, it is a precious resource. Water fit to be drunk is being used for other purposes that can use lesser quality water, such as toilets.
Mixing faeces and urine makes treatment difficult. All waste water treatment plants use some natural/biological processes, but nature does not normally have this waste water, so there are no microbes that can deal with this mix. In order to treat waste, treatment plants have to do this in stages. Each stage treats a different component of the mix by creating the right environment for microbes to do their work (aerobic, anaerobic, anoxic and the right pH). This is costly and requires energy.
A mix of domestic and industrial effluent in water cannot be treated properly, for heavy metals and other pollutants make this water unsuitable for reuse. This is normally discharged into the ground or water bodies.
Because of the complexity of the treatment process, treatment plants tend to be large. This requires costly infrastructure to build and maintain it, often out of the reach of poorer communities.
Each person's urine and manure contain approximately enough nutrients to produce enough food to feed that person. Urea is the major component of urine, yet we produce vast quantities of urea by using fossil fuels. By properly managing urine, treatment costs as well as fertiliser costs can be reduced. Faeces also contains recognised nutrients, and could be used for modern agriculture, as micro-nutrient deficiency is a significant problem. “ecosan”, “dewats”,“desar”, and other abbreviations. They placed their emphasis on the hygenisation of the contaminated flow streams, and shifted the concept from waste disposal to resource conservation and safe reuse.