Safe and sustainable business models for water reuse in aquaculture in developing countries

Abstract

For many people, the nutritional benefits derived from pond-based aquaculture systems can be substantial. The use of wastewater can add additional environmental and financial benefits where freshwater is scarce and nutrients in the wastewater can be recovered as free fish feed instead of contributing to water eutrophication. Wastewater-fed aquaculture has a long history, especially in Asia. While the planned use of wastewater appears to be declining due to increasing urbanization and the concomitant lack of space, unplanned and unsafe water reuse is common because of widespread water pollution. This report examines the win-win situations of planned integrated wastewater treatment and aquaculture production systems that support human nutrition and food security while contributing to the sustainability of wastewater treatment through cost recovery. The report briefly reviews different wastewater-fed fish production systems and explores two empirical business cases from Africa (both public-private partnerships) and one from Asia (a nongovernmental organization and private sector partnership), which have been analyzed for their safety, value propositions, financial feasibility, socioeconomic and cultural acceptance, health risk reduction measures, as well as their scaling-up potential. The main section ends with special attention on the required standards for water quality monitoring given the importance of public health risks and risk perceptions. From an aquaculture entrepreneur’s perspective, the combination of fish farming and wastewater treatment in common waste stabilization ponds (WSPs) allows significant savings on capital (pond infrastructure) and running costs (wastewater supporting fish feed). On the other hand, the party who owns the treatment plant will have the benefit of a partner with high interest in taking direct or indirect care of the plant’s operational and infrastructure maintenance. Like other waste-based businesses, the success of wastewater-based aquaculture depends strongly on market perceptions and acceptance as well as compliance with the regulatory environment, in particular safety guidelines. In wastewater-based production systems, health concerns can relate to many parties, but most affected are the farm workers and fish consumers. While in WSPs, fish are usually reared in the final maturation pond(s) to be followed by depuration and/ or smoking of the fish as measures for risk reduction, an alternative model presented in the report limits the wastewater contact to broodstock. Fish eggs are extracted from the broodstock for the production of fingerlings which are raised in clean water. Another presented alternative is to produce fish feed (only) in the wastewater, such as duckweed, while fish are cultivated in clean water tanks as shown in the case study from Bangladesh. The financial analysis of the presented systems shows profitable options for the fish farmer, operational and in part capital cost recovery for the treatment plant, and as the treatment plant operators can stop charging households a sanitation fee, eventually a triple-win situation for both partners and the served community. The different models and partnership constellations can easily be replicated given the ubiquity of WSP systems, and emphasize the important role of an intersectoral dialogue for turning a highly subsidized waste burden into a potentially profitable business in support of a circular economy.