What is the typical purpose of sedimentation basins in water treatment?

What is the typical purpose of sedimentation basins in water treatment?

• A. To disinfect water.
• B. To mix coagulant.
• C. To evaporate water.
• D. To allow flocs to settle by gravity and remove settled solids from the water.

Answer: (D)

Sedimentation basins are designed to let particles formed after coagulation settle out by gravity. In these quiet, slow-flow zones, the larger and denser flocs settle toward the bottom while the clarified water flows out the top, and sludge is periodically removed. This removal of suspended solids reduces turbidity and helps protect and improve the efficiency of the downstream filtration and treatment steps. Disinfection is a later step, not the purpose of sedimentation. Mixing coagulant happens earlier in the rapid-mix stage, not in a settling basin. Evaporation is not a standard part of conventional water treatment.

Sedimentation basins are designed to let particles formed after coagulation settle out by gravity. In these quiet, slow-flow zones, the larger and denser flocs settle toward the bottom while the clarified water flows out the top, and sludge is periodically removed. This removal of suspended solids reduces turbidity and helps protect and improve the efficiency of the downstream filtration and treatment steps.

Disinfection is a later step, not the purpose of sedimentation. Mixing coagulant happens earlier in the rapid-mix stage, not in a settling basin. Evaporation is not a standard part of conventional water treatment.