TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The flocculant is injected to the wastewater; is added to the wastewater in clarifier, entrapped air flotation system or dissolved air flotation system; is added to wastewater without adjusting pH value of the wastewater; and is added to wastewater in an amount of 1-30 ppm. The solid waste materials are separated from the wastewater by settling; are separated from wastewater in clarifier or flotation unit. The flotation unit is a dissolved air flotation unit or entrapped air flotation unit. The solid waste materials are processed by heating. The solid waste materials are heated to a 70-95 degrees C. The tallow is isolated from the solid waste materials. The solid waste materials are separated in a centrifuge into at least two phases including tallow phase and tallow phase is removed.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The flocculant is cationic acrylamide copolymer, anionic acrylamide copolymer or nonionic acrylamide copolymer. The polyacrylamide or acrylamide copolymer is polyacrylamide, polymethacrylamide, poly-N-methylolacrylamide, poly-N,N-dimethylacrylamide, dialkylaminoalkyl(meth)acrylamide polymer, dimethylaminopropyl methacrylamide polymer and dimethylaminopropyl acrylamide polymer, acrylamide/dimethylaminoethyl (meth)acrylate methyl chloride quaternary copolymer, acrylamide/acrylic acid copolymer, acrylamide/2-acrylamido-2-methylpropanesulfonic acid copolymer or 2-acryloxyethyltrimethylammonium chloride/acrylamide copolymer. The acrylamide copolymer is acrylic acid copolymer containing acrylamidopropyltrimethyl ammonium chloride, methacrylamidopropyltrimethyl ammonium chloride, acrylamidopropyl sulfonate, and/or acrylamide. The acrylamide copolymer is acrylamide copolymer containing dimethylaminoethyl methacrylate, acrylamidopropyltrimethyl ammonium chloride, methacrylamidopropyltrimethyl ammonium chloride, and/or acrylamidopropyl sulfonate. The mole ratio of comonomer to acrylamide in acrylamide copolymer is 1:99-99:1. The polyacrylamide or acrylamide copolymer has number average molecular weight of 500-2000000.