GB1391142A - Dewatering sludge - Google Patents

Abstract

1391142 Dewatering sludge CALGON CORP 19 July 1973 [24 July 1972] 34567/73 Heading C1C An aqueous waste sludge is dewatered by conditioning the sludge with a chemical conditioning agent and subjecting the conditioned sludge to a mechanical dewatering step, the chemical conditioning agent being a watersoluble polymer having a molecular weight of at least 100,000 and containing at least 1À0 mole per cent units of Formula I or II where each of R 1 and R 2 is C 1-18 alkyl or C 7-10 aralkyl or R 1 and R 2 are joined to form, together with the N atom to which they are attached, a heterocyclic group having one or more hetero atoms; R 3 is hydrogen, halogen or C 1-4 alkyl; R 4 is hydrogen, halogen or C 1-5 alkyl; R 5 is C 1-5 alkyl, phenyl or phenyl substituted by one or more C 1-4 alkyl or alkoxy groups; or R 3 or R 4 together with R 5 forms a cyclic group of at least 6 C atoms or a bicyclic group of at least 7 C atoms, which cyclic groups may be substituted by one or more C 1-5 alkyl groups; R 6 is hydrogen or methyl; R z is any group; X<SP>(-)</SP> is an anion and n is 0, 1 or 2. The polymer may be a homopolymer, a copolymer containing units of both Formulae I and II or a copolymer containing units of Formula I and/or II and units derived from other monomers (watersoluble or insoluble) such as acrylamide, methacrylamide, N (C 1-6 alkyl)-acrylamides and methacrylamides, N-vinyl pyrrolidone, di-(C 1-6 alkyl) dialkyl ammonium chlorides, vinylacetate, acrylonitrile, vinyl chloride, C 1-6 alkyl esters of acrylic acid, methacrylic acid and styrene. The anion X<SP>(-)</SP> is preferably a halide ion. The conditioning agents may be used together with organic conditioning agents such as ferric and ferrous salts, and the pH of the sludge may be adjusted by adding lime. The mechanical dewatering step may be carried out by gravity filtration, vacuum filtration, filter press, elutriation, flotation, thickening and preferably centrifugation. The sludge may be treated or untreated municipal or industrial sludge.