Test: Sedimentation Tanks - Civil Engineering (CE) MCQ

Clarifiers are tanks built with mechanical means for continuous removal of solids being deposited by sedimentation. Settling basins are ponds constructed for the purpose of removing entrained solids by sedimentation.

Settling basins are ponds constructed for the purpose of removing entrained solids by sedimentation. Clarifiers are tanks built with mechanical means for continuous removal of solids being deposited by sedimentation.

Based on the method of operation, there are two types of sedimentation tanks. The first one is filled and draw type tank and the second one is the continuous flow type tank.

A layer of accumulated solids called sludge forms at the bottom of the tank and is periodically removed. Prior to sedimentation, coagulants are added to the water in order to facilitate the settling process, which is followed by filtration and other treatment steps.

In case of fill and draw type sedimentation tank, water from the inlet is stored for some time. The time may be 24 hours. The suspended particles settle down. After 24 hours, the water is discharged through the outlet.

Based on the shape of the sedimentation tank, there are two types of sedimentation tank. They are circular sedimentation tank and rectangular sedimentation tank.

In the case of continuous flow type, water is not allowed to rest. Flow always takes place but with a very small velocity. During this flow, suspended particles are settling at the bottom of the tank. The flow may be either in a horizontal direction or vertical direction.

Then settled particle is removed. This removal action requires 6-12 hours. 30-40 hours is required for one complete action in case of fill and draw type sedimentation tank.