GB805526A - Method for clarifying water - Google Patents

Abstract

Water is clarified by mixing with it a coagulant and an acrylamide polymer. The coagulant is chosen from ferrous sulphate, ferric chloride, chlorinated ferrous sulphate, sodium aluminate, aluminium sulphate and aluminium chloride. The acrylamide polymer may be polyacrylamide of a copolymer of acrylamide with up to 15 mole per cent. of other polymerizable substances such as acrylic and methacrylic acids and their alkyl esters, acrylonitrile, methacrylonitrile, methacrylamide, vinyl alkyl ethers, styrene, vinyl chloride and vivylidene chloride. The polymer or copolymer may contain free carboxyl groups, resulting from the copolymerization of acrylamide with acrylic acid, or from the partial hydrolysis of amide groups subsequent to polymerization. The coagulant and acrylamide polymer may each be added in the form of a powder or of an aqueous solution. Where the polymer is added in the form of a powder, it may first be mixed with an inert carrier such as diatomaceous earth, clay, pryrophillite or talc. The process may be applied to the removal of finely divided solids such as silt or clay from river or lake water. In examples (a) alum (with or without sodium silicate) and acrylamide polymer is added to river water, (b) ferric chloride and acrylamide polymer is added to river water, the pH of the water being adjusted to 6 by the addition of sodium hydroxide, (c) an aqueous effluent containing fine coal and clay in suspension, and obtained in the recovery of foundry sand by washing, is treated with aluminium sulphate and acrylamide polymer, and (d) ferric sulphate and acrylamide polymer is added to a brine obtained from a shale formation. Reference has been directed by the Comptroller to Specification 768,665.