Patent ID: 7754086
Filing Date: 2010-07-13
Classification: B01D,C02F

Abstract:
1. A process of dewatering an aqueous suspension in which the aqueous suspension is sewage sludge comprising a) dosing the suspension with a flocculating amount of a first flocculant in which the first flocculant is cationic acrylamide organic polymer of a molecular weight of at least one million to form a thickened suspension, b) adding and mixing into the thickened suspension formed in step a) a dewatering amount of a second flocculant in which the second flocculant is a water-soluble or water swellable polymer formed from 50 to 100% by weight methyl chloride quaternary ammonium salt of dimethylamino ethyl (meth)acrylate and 0 to 50% by weight acrylamide of intrinsic viscosity between 4 and 10 dl/g, wherein the second flocculant is distributed throughout the thickened suspension of part b) using mixing equipment, and c) subjecting the thickened suspension to mechanical compression dewatering to form a cake, characterised in that the second flocculant of step b) is mixed into the suspension in the form of (i) substantially dry polymer particles having a diameter of at least 50 microns or (ii) an aqueous composition comprising dissolved or hydrated polymer having a polymer concentration of at least 2% by weight.