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


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<International Source Book On Environmentally Sound Technologies
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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.

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