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<International Source Book On Environmentally Sound Technologies
for Wastewater and Stormwater Management>

9.1.2 Current wastewater-reuse practice

The term "wastewater" is used generically to cover the range of forms in which human excreta is reused in aquaculture, rather than restricting it to water-borne excreta or sewage. There is great diversity of systems involving cultivation of animals, (mainly fish) (Photo 1) and plants (mainly aquatic vegetables such as water spinach) (Photo 2) (Table 2.6).

Most reuse systems have been developed by farmers and local communities rather than by scientists and engineers; the primary motivating factor has been reuse of nutrients for food production rather than wastewater treatment, and with scant attention to either waste treatment or to public health.

Photo 1: Fish cultured in wastewater-fed East Lake, Wuhan, China

Photo 2: Harvesting water spinach cultivated in sewage in Vietnam.

Fresh excreta or nightsoil may be used directly through overhung fishpond latrines (Photo 3); and nightsoil and septage may be transported (cartage) by various means to fishponds for use as a fertilizer. Overhung latrines are widespread on fish ponds in China, Indonesia and Vietnam. Duckweed is also cultivated in small ponds fertilized directly with nightsoil from a latrine in Bangladesh and is harvested for feeding to fish in nearby ponds. Cartage of nightsoil (manually on foot or bicycle, by boat, or by vacuum truck), and to a lesser extent septage, for use as a fish pond fertilizer is widespread in China and Vietnam.

Photo 3: An overhung latrine on a fish pond in Vietnam

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