New cationic polyelectrolytes synthesized by homopolymerization or copolymerization of allyl-acrylate quaternary ammonium salts with acrylamide (AAm) and diallyldimethylammonium chloride (DADMAC) were tested as flocculants in a baker's yeast waste water. The effect of polymer structure, molecular weight and charge density on the flocculation properties were investigated with respect to total organic content, optical density and volume of sludge. The results were compared with that, of a commercial polyelectrolyte Zetag 7557 (acryloxyethyltrimethylammoniumchloride-acrylamide copolymer) (Allied Colloids). The flocculation results indicated that the efficiency of the new copolymers was similar to commercial polyelectrolyte Zetag 7557 and both polymer bridging and charge patch models are effective.