Activated sludge should have the ability to settle quickly so that it can

Options

A. be rapidly pumped back from sedimentation tank to aeration tank
B. absorb pathogenic bacteria present in watewater while sinking to the botton of the settling tank
C. be discarded and anaerobically digested
D. absorb colloidal organic matter

Answer

A

Explanation

Activated sludge is sedimenation of bacterial flocs into the settling tanks. A part of it is sued as an inoculum in aeration tanks. So, they must have an ability to settle quickly, so that it can be rapidly pumped back from sedimentation tank to aeration tank.