ABSTRACT
Gravity thickening is a sedimentation process for thickening sludge. It is usually operated continuously with flow dependent on plant flow.
The thickener is similar to a circular clarifier except that the bottom has more slope. Sludge enters at the center and solids settle to form a sludge blanket. The thickened sludge blanket is gently stirred by a rake mechanism to release gas bubbles, and to push the sludge to a center sump for removal. Supernatant passes over an effluent weir around the outer rim of the thickener.
The supernatant flow is usually returned to either the primary treatment unit or to a secondary treatment process.
The thickened sludge is usually pumped to either a blending, holding, or surge tank or directly to a dewatering process.
