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Ecological sanitation

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Ecological sanitation, or EcoSan, is the term used in WASH circles to describe sanitation systems which are dispersed (rather than being based on sewers and large municipal wastewater treatment works) and which aim to encourage people to view their own waste as a potential resource rather than as a problem.[1] This has wide applicability in countries that have complex sewerage systems as the "flush and forget" mentality is found almost everywhere.

Ecosan and composting toilets are terms that are often used interchangably and can be poorly defined. It is probably best to consider composting toilets as part of Ecological Sanitation, which can and should contain a range of other processes.

Features[edit]

The UNDP lists the principles of ecological sanitation as follows:

  • Prevent disease - must be capable of destroying or isolating faecal pathogens;
  • Protect the environment - must prevent pollution and conserve valuable water resources;
  • Return nutrients - must return plant nutrients to the soil;
  • Culturally acceptable - must be aesthetically inoffensive and consistent with cultural and social values;
  • Reliable - must be easy to construct and robust enough to be easily maintained in a local context;
  • Convenient - must meet the needs of all household members considering gender, age and social status;
  • Affordable - must be accessible to all households in the community.

Resource recovery[edit]

The end-of-pipe sanitary systems that are used today are based on the modern misconception that human excreta are simply wastes with no useful purpose and must be disposed of.[2]

The resources contained in excreta and wastewater are recovered in ecosan and reused. These resources in wastewater are:

  • Nutrients, which can be used for agriculture.
  • Energy; biogas or other substances/products can be made/derived from human and animal waste- see Energy from wastewater. This is often not a focus of EcoSan

Technologies used in ecosan[edit]

  • Composting toilets
  •  ?

In practice[edit]

In practice, Ecosan is used to describe devolved sanitation systems whereby users are expected to manage their own systems and (usually) deal with their own sludge. People often mean different things, but usually it involves a Composting toilet, which might be a Single pit latrine, a Single Ventilated Improved Pit latrine or a Double Ventilated Improved Pit latrine whereby users have added ash, sawdust or other material in an effort to encourage breakdown and the destruction of pathogens. Material is usually stored for an extended period of time, sometimes is subject to secondary treatment (such as co-composting) and spread to agriculture.

Urine Diversion Dry Toilets are often considered to be a useful concept in ecosan as the urine has a relatively low risk of pathogen infection, and so can be kept clean and used directly in agricultural production.

This concept might be contrasted with Open defecation where untreated excrement is left on the soil surface as a waste and health hazard and even large pit latrines where sludge is left in a large tank over a period of time and is liable to drain into groundwater and affect the quality of drinking water.

Use of feces from composting toilets[edit]

To reduce risk, material from composting toilets should never be put directly onto food crops. After the recommended storage time of the feces in the chambers of the composting toilets has expired, the material is moved (ideally with minimum handling) and given a secondary treatment. The simplest secondary treatment systems are community scale co-composting or vermiculture, which have shown to be effective at sanitisation if managed properly.

During this treatment, workers may be at high risk of infection, so need to wear protective clothing. Even after treatment, feces compost should not be used on any food crop which will come into direct contact with humans - such as leaves or tubers. Ideally the compost should never be used on food crops at all.

References[edit]

Ecological Sanitation Handbook 2004, Stockholm Environment Institute

See also[edit]