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GRAVITY THICKENER (SEDIMENTATION) Gravity thickener is essentially a sedimentation process similar to the process that occurs in all settling tanks. It is the most common process currently used for dewatering and for the concentration of sludge before digestion. It is accomplished in a sedimentation tank in which solids separate from liquid phase by settling. The settled solid are concentrated by the action of gravity by virtue of the weight of the overlying solid. First, the feed will enter to the feedwell, as it moves down to the feedwell flocculant is injected so that as it moves down to the feedwell, flocculation and deaeration occur. Flocculant causes fine particles to bind together and settled rapidly. The flocculant feed will go down to the rake arms. The rake arm rotates slowly with the scraper blades on the bottom to push the solids in the thickener to the deflector cone. The deflector cone is the cone shaped discharged located in the center of the thickener. Once the solids enter the deflector cone, they are removed by pumps, pumping the concentrated solid underflow to a conditioning tank. The clear water overflows at the top of the thickener which channels the clear water to the overflow discharged. The overflow is pumped from the thickener. Drive Uni
