Biotreatment of fish farm effluents using the cyanobacterium Phormidium bohneri

The potential environmental impact of effluent from fish farms is of increasing environmental concern. Although concentrations in total nitrogen and phosphorus are usually low, their impact on the environment cannot be ignored because of the high nutrient mass flows utilized during fish farming. In this paper we investigated the use of a non-toxic cyanobacterium, Phormidium bohneri, to remove dissolved inorganic nutrients from fish farm effluents. Wastewater was directed toward three completely mixed 70 1 photobioreactors with retention time of 8, 12 and 24 h, respectively. Average efficiencies of ammonia nitrogen removal from rainbow trout (Oncorhynchus mykiss) effluent was 82% and 85% for soluble orthophosphate, over a 1 month period. From these results, the potential use of P. bohneri as an alternative for the tertiary treatment of fish farm effluents is analyzed. (C) 1998 Elsevier Science B.V.