SOUTH DAKOTA Department of
Environment & Natural Resources

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Surface Water

Clarifierspicture of a clarifier

Primary Clarifiers slow the speed of the wastewater to allow solids to settle out of the wastewater. Secondary Clarifiers are used to settle out microorganisms from the activated sludge process.

Clarifiers typically have rotating arms, such as the one that is shown in this picture, to remove scum from the surface of the water.

Clarifiers are usually either round or rectangular in shape. The sludge or biosolids are collected at the bottom of the clarifier and sent to a digester for further treatment.

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