During Secondary Aerobic Wastewater Treatment,some of the Activated Sludge Goes

Multiple Choice

During secondary aerobic wastewater treatment,some of the activated sludge goes ________ while the rest goes ________.

A) back to the aerator / to the anoxic sludge digestor
B) back to the primary system / to the aerator
C) to the anoxic digestor / back to the primary system
D) back to the primary system / to the tertiary digestor