A case study of a pilot high rate algal pond for the treatment of fish farm and domestic wastewaters

BACKGROUND: Microalgae-based technologies have emerged as a promising approach for simultaneous wastewater treatment and fish food production able to overcome the main limitations in the aquaculture sector. The current study focused on the mechanisms of carbon and nutrient removal from fish farm and domestic wastewaters in a 180 L outdoors pilot high rate algal pond (HRAP) at different hydraulic retention times (HRTs) considering water evaporation losses. RESULTS: Maximum chemical oxygen demand, total Kjeldahl nitrogen and total phosphorus removal efficiencies of 77 ± 9%, 83 ± 10% and 94 ± 6%, respectively, were recorded during the treatment of fish farm wastewater at 10 d of HRT. Carbon and nitrogen were removed by assimilation into biomass (52 ± 12% and 74 ± 22%, respectively) and stripping, while phosphorus was mainly assimilated into biomass (69 ± 23%). Carbon stripping, along with the low carbon and nutrient loading rates supplied, resulted in low biomass productivities (maximum of 5 g m −2 d −1 ). A successful solids removal was achieved in the settler (82 ± 18%), which entailed effluent solid concentrations below the maximum permissible discharge limit.