Abstract: A process is disclosed for treating food wastewaters by acidifying to a low pH, adding an alginate, and, preferably, adding lime to a pH of at least 7.0, without adding iron or aluminum to assist in coagulation and flocculation of the wastewater. A floc is formed at acid pH in some wastewaters and at neutral to alkaline pH in other wastewaters treated with lime. After recovery of the floc as a sludge, the process provides at least about 70% removals of Total Suspended Solids (TSS), Biochemical Oxygen Demand (BOD), and Chemical Oxygen Demand (COD) at reasonable costs and with negligible formation of free fatty acids in the resulting sludge.

Abstract: A process is described for treating a feed wastewater from a food preparation plant to recover substantially all of its fats and up to 50% of its proteins in a chemical float sludge which is selectively admixed with an absorptive bulking agent, such as sawdust, at a dry-basis weight ratio of 3-4 pounds of bulking agent to one pound of total sludge solids to produce a biomass mixture which is selectively dried and regulated in size to a maximum of 1/8-inch to produce a biomass fuel, characterized by a fuel value of approximately 11,000 Btu per pound, which is highly suitable for self-sustained burning in a gasifier-type suspension burner. After removal of the float sludge, the partially purified wastewater is aerobically treated with microorganisms to produce activated sludge, a selected portion thereof being recycled to the feed wastewater before admixing coagulation and flocculation chemicals therewith.