Question

Sewage treatment process in which part of decomposer bacteria is recycled into starting of the process is called

• A. Primary treatment
• B. Tertiary treatment
• C. Cyclic treatment
• D. Activated sludge treatment

Answer 1

The correct option is D Activated sludge treatment

Introduction to sewage treatment

Sewage treatment involves the removal of solid suspended particles and the reduction in the amount of organic matter. The treatment of sewage is usually carried out in two main steps which are the following:-

Primary treatment:

Solid suspended particles are removed using filtration and sedimentation.

Secondary treatment:

Organic matter is oxidised using microbes.

Secondary treatment of sewage

During the secondary treatment of sewage, the primary effluent undergoes the following stages:-

Aeration tank:

The primary effluent is aerated resulting in the growth of flocs.

Settling tank:

The flocs settle down to form a sediment called activated sludge.

Anaerobic digesters:

• The activated sludge made up of decomposers is made to flow into anaerobic digesters.
• Some of the activated sludge is pumped back as inoculum into the settling tank. Therefore, this is called activated sludge treatment.

Final answer: (d)