Question

What happens to activated sludge?

• A. It is generally released into natural water bodies like rivers and streams
• B. It is completely pumped back into aeration tank to serve as inoculum
• C. The major part of the sludge is pumped into large tanks called anaerobic sludge digesters
• D. It undergoes sequential filtration

Answer 1

The correct option is C The major part of the sludge is pumped into large tanks called anaerobic sludge digesters

Once the BOD (biochemical oxygen demand) of sewage or waste water is reduced significantly, the effluent is then passed into a settling tank where the bacterial ‘flocs’ are allowed to sediment. This sediment is called activated sludge. A small part of the activated sludge is pumped back into the aeration tank to serve as the inoculum. The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digesters.