Effluents from an Aquaculture Research Station and Stream Water Quality

Abstract

Lower Station of the E. W. Shell Fisheries Center discharges into Saugahatchee Creek. Ponds of the Fish Genetics Research Unit and the Aquaculture Production Research Unit are the main sources of anthropogenic pollution to Lower Station Creek. However, the Fish Genetics Research Unit effluent enters the stream above the water supply reservoir (FP-11). Natural, biological and physiochemical processes in FP-11 improve water quality, and outflow from FP-11 is of superior quality to water in Lower Station Creek upstream of the Fish Genetics Research Unit. Thus, the main source of pollution to Lower Station Creek is discharge from the Aquaculture Production Research Unit. Concentrations of total nitrogen, total phosphorus, chloride, total alkalinity, total hardness, specific conductance, total suspended solids, turbidity, and biochemical oxygen demand increase between the outflow of FP-11 and the entrance of Lower Station Creek into Saugahatchee Creek. The major increases in concentrations of the variables tend to occur during fall and early winter when ponds of the Aquaculture Production Research Unit are drained for harvest. The highest concentrations of potential pollutants are discharged in the final stages of draining a pond for harvest. Effluents from ponds at different stages of drawdown are combined in the common drains tending to mash the concentration peaks at the outfalls of the common drains. Because a large portion of the pollution is discharged during pond draining, measures to reduce overflow from ponds during the rest of the culture period do not have a large effect on annual pollution loads. Water quality at the mouth of Lower Station Creek is better than water quality in Saugahatchee Creek. Thus, discharge from the Lower Station does not contribute to further water quality degradation in the already-polluted Saugahatchee Creek. Discharge of Lower Station Creek has higher concentrations of several possible pollutants than typically found in less-polluted streams, but only total suspended solids and turbidity exceeded concentration limits typically imposed on effluents discharged into Alabama streams classified for fish and wildlife propagation. The Lower Station produces over 45,454 harvest kilograms of fish annually and discharges 30 days or more per year. According to the U.S. Environmental Protection Agency rules, it is a concentrated aquatic animal production (CAAP) facility and qualifies for National Pollutant Discharge Elimination System (NPDES) permitting. In Alabama, NPDES permits for effluents from CAAP (aquaculture) facilities apparently will require implementation of best management practices (BMPs). The only practical means of removing suspended solids and turbidity from the discharge of the Aquaculture Production Research Unit would be retention for at least 24 hours in a sedimentation basin before final discharge.