Water recycle is an important part of the coal preparation process. This study was directed toward (1) a survey of current practice and an evaluation of both the solid and liquid components of blackwater, (2) an experimental study of blackwater flocculation, and (3) a fundamental analysis of the flocculation process. The solids contained in the blackwater discharge to the fine refuse thickener of a coal preparation plant were found to contain, on average, 56% coal and 44% mineral matter. The mineral matter was largely illitic clay, while the water phase contained relatively large amounts of so4= and ca++. Detailed studies were made of both natural and synthetic flocculants and the influence of polymer type and ph on the settling rate, turbidity of the supernatant liquid, and sludge volume of the settled solids. More fundamental studies were made that clearly indicate the need for controlled mixing of polymer into the suspension to be flocculated and the need to evaluate more closely the structure of the flocs formed during the process.