Sedimentation of solids is accelerated and complete, resulting in a high-quality effluent, when a 0.1% soln. of equal parts of poly(dimethyl-diallyl-ammonium chloride) cationic flocculant and a nonionic or anionic polyacrylamide is used at a rate of 0.25-4 mL/L wastewater. Thus, briquet manufg. wastewater contg. 5-10 g solids/L was treated with the above mixt. at 0.5 mL/L under turbulent mixing conditions, flocculanted for 15 min and allowed to settle for 30 min, forming a brown coal sludge having >100 g solids/L. The effluent contained <50 mg solids/L. [on SciFinder (R)]