GB816399A - Improvements in the agglomeration of suspended particles in aqueous media - Google Patents

Abstract

A method of improving the agglomeration of suspended particles in aqueous waste media having a biochemical oxygen demand such as organic wastes, comprises adding an inorganic coagulant and one or more synthetic polymeric water-soluble polyelectrolytes having an average molecular weight of at least 10,000 and having a structure derived by the substantially linear ploymerization of at least one monoolefinic compound through the aliphatic unsaturated group. The ployelectrolytes may be homopolymers of acrylic or methacrylic acid or their derivatives such as the alkali metal and ammonium salts of acrylic acid or of methacrylic acid, acrylamide, methacrylamide, the N-alkyl substituted amides, the N-aminoalkylamides and the corresponding N-alkylaminoalkyl substituted amides, the aminoalkyl acrylates, the aminoalkyl methacrylamides and the N-alkyl substituted aminoalkyl esters of either acrylic or methacrylic acids, or copolymers thereof with copolymerizing monomers such as ethylene, propylene, isobutylene, styrene, a -methylstyrene, vinyl acetate, vinyl formate, alkyl ethers, acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, the alkyl acrylates, the alkyl methacrylates, the alkyl maleates and the alkyl fumarates. The polyelectrolytes may be used in amounts from 0,1 to 1,000 parts per million, preferably from 0,5 to 5 parts for dilute wastes and from 3 to 240 parts for concentrated sludges. The inorganic coagulant may be alum, hydrated lime, a ferrous salt, a ferric salt, aluminium sulphate, calcium carbonate or chloride, or zinc chloride, and may be added first. The invention is exemplified with municipal sewage, activated sludge, Guggenheim process sludge (where the coagulant, ferric chloride, is added in the Guggenheim treatment), mixed domestic sewage and industrial waste, textile wastes from the finishing of synthetic fibres, beet sugar processing waste, tannery effluent, cotton mill wastes, tannery-wastes (treated with 7 lbs. lime per 1,000 gallons prior to the present treatment), laundry waste, starch wastes from wool felt processing, paper de-inking wastes, raw sewage sludge containing industrial wastes, and digested sewage sludge. The invention may be applied also to oil wastes, stillage, milk, dairy, rubber plant, cornstarch, meat packing and slaughterhouse wastes and fermentation residues. Reference has been directed by the Comptroller to Specifications 768,662 and 768,665.