Faecal sludge management (FSM) is the collection, transport, and treatment of fecal sludge from pit latrines, septic tanks or other onsite sanitation systems. Fecal sludge is a mixture of human excreta, water and solid wastes (e.g. toilet paper or other anal cleansing materials, menstrual hygiene materials) that are disposed of in pits, tanks or vaults of onsite sanitation systems. Fecal sludge that is removed from septic tanks is called septage.
FSM is necessary in densely populated areas where a proportion of the population is not connected to a sewerage network, and the covering and rebuilding of pit latrines is not possible. This is the case in most urban areas in developing countries, but such services are also used in developed countries where sewerage systems are unavailable. FSM services are usually provided by formal and informal private sector services providers, local governments, water authorities and utilities. However, in many developing countries FSM services are often unavailable, or if they are available are often informal, unregulated, unhygienic and unsafe. This can lead to surface water and groundwater pollution, the spreading of pathogens into the environment and adverse public health impacts. It can also result in unreliable services with relatively high costs to the households which need them.
Faecal sludge collection services can be made available on a scheduled basis or on a call-for-service basis (also known as on-demand, on-request or non-scheduled services). The collected fecal sludge may be transported to treatment plants using a vacuum truck; a tank and pump mounted on a flatbed truck; a small tank pulled by a motorcycle; or in containers on a hand cart. Mobile or permanent transfer stations can be used to improve the efficiency of fecal sludge transportation by transferring the waste to larger tankers for haulage to treatment. The wider use of multiple decentralized sludge treatment facilities within cities (to avoid long haulage distances) is currently being researched and piloted.
The collected fecal sludge should preferably be processed at dedicated fecal sludge treatment plants, instead of being co-treated with sewage in municipal sewage treatment plants, unless these plants are able to take the additional load, and facilities to separate liquids and solids are available. A variety of mechanized and non-mechanized processing technologies may be used, including constructed wetlands, anaerobic digestion, and waste stabilization ponds. The treatment process can produce useful products such as treated effluent that can be used for irrigation. Another possibility is to use the treated fecal sludge after composting as a soil conditioner or for the production of biogas, charcoal, biodiesel, powdered industrial fuel and electricity. Historically, the term night soil was used for fecal sludge.
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