Use of coagulants to treat seafood processing wastewaters

A Sea Grant-funded project was initiated in 1978 to study suspended solids (TSS) removal from seafood processing wastewater. The initial phase of the project involved a series of laboratory and pilot plant tests using hydrocyclones as solids-liquid separation devices. Our testing was used to ascertain appropriate coagulant dosages, pH, mixing time, and other parametes. Next, pilot plant testing was performed in Kodiak to confirm feasibility of the proposed system. Results indicate that hydrocyclones followed by coagulant addition and dewatering can produce a clarified effluent low in particulates and concentrate TSS by a factor of approximately 100. Chitosan and ferric sulfate were effective coagulants for crab, salmon, and shrimp processing wastewaters. The proposed system may not be economical for Alaskan processors, but changes in the by-product market can alter this conclusion.