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Ecological sanitation, also known as ecosan, is a modern alternative to conventional sanitation techniques. The objectives are to offer economically and ecologically sustainable and culturally acceptable systems that aim to close the natural nutrient and water cycle. Unlike most traditional sanitation methods, ecological sanitation processes human waste to recover nutrients that would otherwise be discarded.
Additional recommended knowledge
Introduction to ecological sanitation
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, minimize 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. 
According to the 10 Recommendations for Action, published at the 2nd international ecosan symposium 2003 in Lübeck, Germany, the main objectives of ecological sanitation are :
History of reuse-oriented sanitation approaches
In a very broad sense the recovery and use of urine and faeces has been practiced over millennia by almost all cultures. The uses were not limited to agricultural production (although for modern application this may be 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. It is reported that 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-storey 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 great 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 utilized when planting maize.
In the Middle Ages, the use of excreta and greywater 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. 
Concepts of ecological sanitation
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. 
According to Esrey et al. (2003)  ecological sanitation can be defined as a system that:
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. 
The figure below shows the potential positve impacts of an optimal ecosan approach:
Thus, the most important advantages of ecological sanitation systems are:
Technologies of ecosan systems
It is not easy to determine ecosan systems as ecological sanitation is not just one specific technology, but a new approach based on an ecosystem-oriented view of material flows.
The following diagram gives an overview of the different collection, treatment and reuse possibilities of the five flow streams considered in ecological sanitation systems:
Further information on ecosan technologies can be found in "Ecological Sanitation" by Winblad et. al. , in "Toilets that make compost" by Peter Morgan  or in the gtz-ecosan technical data sheets , among other relevant literature.
Examples for ecosan projects can be found among others in the collection of project data sheets of gtz ecosan  or on the Enhanced Global Map of ecosan activities by EcoSanRes . In the following some examples are given that underline the diversity of ecosan projects:
Gunaxi province, China - large-scale project of urine diverting dehydration toilets The dissemination programme of ecological dry toilets for Guanxi 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 fertilizer 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 + greywater treatment The sanitation concept of the modern office building “Ostarkarde” of the KfW Bankengruppe in Frankfurt is based on a separate excreta and greywater collection. While urine and faeces are collected via vacuum toilets and a vacuum sewerage using much less water for flushing, the greywater from hand washing and kitchen is collected and treated separately in a compact activated sludge reactor combined with membrane filtration. The treated greywater is then reused for toilet flushing and cleaning water. The amount of greywater 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. 
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Ecological_sanitation". A list of authors is available in Wikipedia.|