Fecal sludge management

Fecal sludge management (FSM), also spelled faecal sludge management in British English, is a management system that safely collects, transports, and treats fecal sludge (also called septage) from pit latrines, septic tanks or other onsite sanitation facilities (OSSF). In other words, it deals with the mixture of human excreta and water that is collected in certain types of decentralized toilets and sanitation systems, instead of going into centralized Wastewater systems. FSM is particularly important in quite densely populated areas where much of the population is not connected to sewerage network, as is the case in most urban areas of developing countries. FSM is generally carried out as a service by local governments, water authorities, water utilities or the formal or informal private service providers. In many developing countries, however, this service is often not provided at all or not done properly, leading to, among others, surface water and groundwater pollution, spreading of pathogens into the environment, adverse health impacts and relatively high costs to households.

For citywide programs in developing countries, fecal sludge collection may be either on a scheduled or on a call-for-service basis. If the fecal sludge is liquid enough, it is usually collected by using vacuum pumps or centrifugal style booster pumps. A variety of manual and motorized devices designed to excavate thick and viscous sludge and accumulated trash are also available in the market.

The collected fecal sludge may be transported to treatment plants via a vacuum truck, a motorcycle tanker, or even a hand cart. Often, mobile or permanent transfer stations are used to improve the efficiency of fecal sludge transportation.

This material should preferably be processed at dedicated fecal sludge treatment plants, instead of being co-treated with sewage in municipal sewage treatment plants, unless these are able to take the additional load. A variety of mechanized and non-mechanized technologies may be used, including constructed wetlands, anaerobic digestion, and waste stabilization ponds. Useful products of the treatment process may include treated effluent that can be used for irrigation, biosolids that can be utilized as a soil amendment in agriculture, biogas, biodiesel, and electricity. These have the potential to offset some of the costs of the program, thereby reducing tariffs for the public. However, value addition all the way to biogas, biodiesel and electricity is difficult to achieve in practice due to technological and operational challenges.

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