Effluent volume and pollutant loads at an inland, low-salinity, shrimp farm in Alabama

An inland, low-salinity shrimp farm in Alabama released 50–60% of stored water during harvests in 2008 and 2010. Maximum concentrations of potential pollutants occurred in the final 5% of water discharged from ponds during harvest. Average, weighted concentrations of variables were lower than maximum values, but greater than concentrations in the receiving stream upstream of the farm outfall. Nevertheless, chloride was the only variable for which the concentration found downstream of the farm outfall exceeded the permissible concentration limit of the Alabama stream classification system. Pollutant loads per tonne of shrimp for the 2 years averaged were 444.9 kg total suspended solids, 51.3 kg 5-day biochemical oxygen demand, 15.2 kg total nitrogen, 1.33 kg total phosphorus, and 4402 kg chloride. Concentrations and loads of most potential pollutants could be lessened by passing farm discharge through a settling basin before final discharge, releasing less water during harvest, and improving the feed conversion ratio.

► An inland shrimp farm discharged about 50% of pond water during harvest.
► Water discharged had elevated concentration of several potential pollutants, especially dissolved salt.
► Nitrogen and phosphorus discharge was 1.33 kg phosphorus and 15.2 kg nitrogen per tonne shrimp.