Patent ID: 7749392
Filing Date: 2010-07-06
Classification: C02F

Abstract:
1. A process of dewatering sewage sludge employing a flocculating system comprising i.) treating the suspension with a flocculating amount of a first flocculant which is a cationic acrylamide and a dewatering amount of a second flocculant, and ii.) subjecting the suspension to mechanical compression dewatering to form a cake, wherein the first flocculant brings about flocculation and assists thickening with the release of free water from the suspension and the second flocculant further dewaters the suspension, wherein the second flocculant is distributed throughout the thickened suspension with mixing equipment, characterised in that the second flocculant is a water-soluble or water swellable polymer that is mixed into the suspension in the form of an aqueous composition comprising dissolved or hydrated polymer having a Brookfield viscosity of at least 400,000 cps (measured at 20° C., RVT viscometer, spindle 6, 1rpm) and the second flocculant is a polymer of 50 to 100% by weight methyl chloride quaternary ammonium salt of dimethyl aminoethyl (meth)acrylate and 0 to 50% by weight acrylamide and the molecular weight of the first and second flocculants is at least 1,000,000.