Recovery and characterization of by-products from egg processing plant wastewater using coagulants

The effectiveness of precipitation or coagulation technology to treat commercial egg processing plant wastewater, using such coagulants as lignosulfonate, bentonite, carboxymethylcellulose, and ferric chloride, was evaluated. For simulated and industrial waste-water, chemical oxygen demand, turbidity, and total solids were reduced over 90, 97, and 95%, respectively, for all coagulants tested. Protein and fat recoveries were over 95% for all coagulants. The optimal coagulant concentration for maximum by-product recovery depended on initial wastewater concentrations of protein, total solids, and fat. The dried by-products contained high concentrations of protein (30 to 50%) and fat (30 to 40%) and had similar essential amino acid profiles as standard proteins from the United Nations Food and Agricultural Organization (FAO). The relative protein digestibilities of each recovered solid (carboxymethycellulose, lignosulfonate, bentonite, and ferric chloride) and corn meal relative to a liquid whole egg standard were approximately 80, 90, 60, 30, and 56%, respectively. These compositional and in vitro digestibility studies suggest that the recovered by-products could be useful as livestock feed ingredients or for other applications.