Circular clarifier apparatus and method

Abstract

This application relates to a circular clarifier for separating and removing separable matter, such as suspended solids, from a liquid. The invention may be used, for example, for separating return activated sludge from clarified liquor using a gas flotation process. The clarifier includes a plurality of fluid feed ports for introducing influent into selected treatment cells of the clarifier in a timed sequence, thereby achieving batch flotation of solids or other separable matter in a continuous infeed process. A plurality of spaced-apart, rotating flocculent handling assemblies traverse the treatment cells for sequentially conveying flocculent into spaced-apart, radially extending collection troughs. All of the flocculent handling assemblies may be driven by a single drive means. Each flocculent handling assembly includes a submerged beach and a scraper assembly including a scraper blade which extends upwardly from the beach. The beaches provide a shear plane underneath the surface layer of flocculent. The scraper assembly includes means for lifting the scraper blade in the vicinity of a trough to enable the blade to traverse over the trough and then descend to a position in contact with or proximate to a corresponding beach. Methods of using the clarifier to more efficiently handle return activated sludge or other fragile flocculent are also described. The clarifier may be stand-alone or adapted to retrofit existing circular primary or secondary sedimentation clarifiers.