Confronting the realities of wastewater aquaculture in peri-urban Kolkata with bioeconomic modelling

Wastewater reuse for aquaculture is a reality in several Asian countries, however, traditional practices face constraints including inadequate or contaminated wastewater inputs and growing concern over health risks. Based on Kolkata and a wastewater flow of 550,000 m3 d−1, rational and conventional designs for lagoon-based wastewater treatment and reuse through aquaculture were compared using bioeconomic modelling. Outcomes showed the rational design required a larger area than the conventional or traditional systems, but that financial returns, nutrient retention and fish production were higher; gross fish production employing rational and conventional designs was 45,500 and 11,560 t, respectively. However, limited land availability and constraints to reconfiguring the existing system make implementation of the rational design unlikely. Findings suggest traditional practices could be enhanced by adopting wastewater treatment prior to reuse, modifying fish production strategies, and monitoring to safeguard health. Bioeconomic modelling constitutes a useful tool in comparing treatment and reuse options, permitting the sensitivity of financial returns to changing costs and recent revisions to WHO guidelines for safe wastewater reuse to be assessed, however, social and environmental consequences demand consideration.