Newsletter and Technical Publications
<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