Suspended solids are removed from wastewaters and waters contg. 10-4-10 g solids/L using poly(di-Me diallyl ammonium chloride) and a water-sol., highly branched, high mol. copolymer of di-Me dially ammonium chloride and 0.1-3.0 mol% of a crosslinking comonomer, e.g., Me triallyl ammonium chloride, tetraallyl ammonium chloride, triallyl amine hydrochloride, N,N,N',N'-tetraallyl ethylenediamine hydrochloride, or methylene bisacrylamide. The flocculant is used at an amt. of 0.05-2%, based on the solids, and at 278-340 K. The method effectively removes iron hydroxide sol 10-4 g/L from water. [on SciFinder (R)]