Wisconsin DNR Wastewater Operator Certification Practice Test

What is the function of Waste Activated Sludge (WAS) in the activated sludge system?

WAS adds solids to the aeration basin. WAS returns solids to the aeration basin. WAS is sludge removed from the system to control MLSS and maintain treatment efficiency. WAS is treated in the digester.

Correct Answer:

WAS is sludge removed from the system to control MLSS and maintain treatment efficiency.

Explanation:

Waste Activated Sludge is removed from the mixed liquor to keep the solids concentration, MLSS, at the proper level. This control is essential because too many suspended solids in the aeration basin slows oxygen transfer, harms sludge settling, and reduces treatment efficiency. By removing excess sludge, the system maintains stable biomass conditions for effective organic matter removal and consistent effluent quality. The solids that are removed are typically thickened and sent for digestion or disposal; returning solids to the basin is done by the return activated sludge, not WAS.

Access more questions from this quiz

Continue to Wisconsin DNR Wastewater Operator Certification Practice Test for more practice questions and the full quiz experience.

Access More Questions