An aq. soln. of cationic, high mol. wt. poly(diallyldimethylammonium chloride) (I) [26062-79-3], synthesized in very alk. soln. with a ternary initiation system, is added in amts. of 0.25-4.0 mL/L to accelerate sedimentation of solid particles from coal-contg. wastewaters. Thus, 0.5 mL of a 0.1% aq. soln. of I was mixed thoroughly with 5-10 g/L coal-solids contg. wastewater from a briquet factory to produce macroflocs and completely sep. coal particles and water in <1 h, giving a sediment contg. solids >100 g/L and a supernatant contg. <100 mg/L. [on SciFinder (R)]