Newsletter and Technical Publications
<International Source Book On Environmentally Sound Technologies
for Wastewater and Stormwater Management>
9.1.5 Stage of development of society
A review of the history and current status of wastewater-fed aquaculture
(Edwards, 2000) suggests that it may progress through three successive
developmental phases depending on the stage of development of society (box 2):
A major question is can those societies in which wastewater-fed aquaculture
currently exists, and those in which it has potential, move from phase 2 to 3?
Without favourable policy to recognize and capitalize on the social and
environmental benefits of wastewater-fed aquaculture, and to introduce adequate
environmental pollution control, the practice is likely to continue to decline.
Major constraints in developed countries, which increasingly correspond to phase
3, are an increase in living standards, improved sanitation and imagined public
health problems. With rising living standards there is a change in consumer
preference from low-value herbivorous and omnivorous species that can be
cultured in wastewater-fed systems to higher-value carnivorous fish and shrimp.
This trend is being compensated for to some extent by a general increase in the
price of fish so that fish species previously considered unacceptable are being
marketed throughout the world. Improved sanitation is also increasingly
associated with decreased availability of wastewater for reuse because of the
increasing trend to install mechanical wastewater treatment systems. Perhaps the
most serious constraint, despite a growing environmental awareness as
educational standards rise, is the real or imagined threat to public health from
pathogens and pollutants. National food regulatory agencies are likely to oppose
the concept of wastewater reuse because of both public health, and social or
aesthetic concerns. An example to support this contention is experience in the
USA where during the 1970s several experimental waste reuse systems were studied
but none have ever been implemented commercially (Ryther, 1990).
|Box 2. Developmental phases in wastewater-fed aquaculture
- Phase 1 - wastewater-fed aquaculture developed in densely populated,
pre-industrial societies in which limited resources favoured waste reuse.
On-site sanitation or cartage and available sites also favoured the
development of the practice
- Phase 2 - the installation of wastewater in early or rapidly industrializing
societies initially favoured wastewater-fed aquaculture by providing
a more readily available source of nutrients. However, rapid urbanization
and industrialization soon limit the practice because of numerous constraining
factors as illustrated by recent experience of most current systems
in Asia today. Rapid urbanization leads to high opportunity cost and
limited availability of peri-urban land; and hypereutrophication of
surface waters may constrain the practice because of excessive organic
matter and nutrient levels. Rapid industrialization without adequate
pollution control leads to increasing volumes of mixed domestic and
industrial wastewater streams. A policy vacuum in most developing countries
limits the introduction and enforcement of favorable social and environmental
legislation that would favour wastewater-fed aquaculture, including
the crucial control of industrial effluents to safeguard public health.
- Phase 3 - a hypothetical late industrial phase in which there is environmental
awareness in society about the need to close nutrient cycles and reuse
wastewater; and favourable policy to implement industrial wastewater
control and monitoring so that the practice is safe from a public health
point of view.