Aquaculture wastewater management presents unique problems in treatment technology. Current methods employ settling of biosolids (fish and uneaten feed) as the primary means of treating aquaculture wastewater. Due to their fragile nature and constant contact with water, biosolids break into smaller sizes during waste collection. The suspended solid fraction, which requires more time to settle out, is carried into other rearing ponds of the receiving stream instead of being piped into offline settling basins. These solids represent a significant impact to receiving streams. Polyacrylamide (PAM) is effective in reducing soil and associated nutrient losses in irrigated agriculture by complexing soil particles to increase settling rate. PAM has also been shown to reduce bacteria and may reduce dissolved nutrients in wastewater. We propose to identify appropriate PAM products and determine concentrations which cost-effectively improve water quality of aquaculture waste supernatant through improved settling efficiency of fish waste. Reductions in suspended solids, phosphorus, nitrogen, BOD, and bacteria will be quantified in treated test solutions of fish waste. Phosphorus leach rates from treated solids and residual PAM levels in supernatants will be determined. ANTICIPATED RESULTS & POTENTIAL COMMERCIAL APPLICATIONS OF RESEARCH Successful development of PAM treatments for aquaculture wastewater will provide a cost-effective means of recovering additional biosolids and associated nutrients from aquaculture discharges through more efficient settling. Employing PAM in aquaculture waste management will improve water quality, help reduce undesirable aquatic vegetation in receiving streams, and may facilitate reuse of nutrients through stabilization of solids and reduce leaching. PAM-enhanced settling may allow for increased fish production without additional impacts to the resource. Treatment of turbid water supplies in low flow facilities could also improve fish health and provide for additional production using otherwise marginal water supplies.
