4. Reaction Clarifiers/ Solid Contact Clarifiers The solids contact clarifier employs a recycle solids contact principal for flocculation, sedimentation, and clarification in a single basin. The system features a concentric drive unit and mixer combination. The slow speed impeller recirculates fresh precipitate through the recirculation drum. The formulation of settleable floc particles occurs in the mixing reaction cone. An automatic sludge discharge system maintains the solids volume along the clarifier bottom. Solids contact units are used for the removal of turbidity for lime softening, and for chemical coagulation in municipal and industrial applications.