alabama-wastewater-operator-grade-2 Practice Test

1Single Choice

In the activated sludge process, what is the primary purpose of returning activated sludge (RAS) from the secondary clarifier to the aeration tank?

A.To increase the dissolved oxygen concentration in the aeration tank
B.To maintain a sufficient concentration of active microorganisms in the aeration tank
C.To reduce the amount of waste activated sludge that must be disposed of
D.To prevent the formation of nitrogen gas in the aeration tank

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