The steps involved in the production of biogas in sewage treatment plant takes place in the sequence of:
(A) Small part of activated sludge is added into aeration tank.
(B) Anaerobic bacteria produces mixture of gases called biogas.
(C) The effluent is passed into a settling tank where the bacterial ‘flocs’ are allowed to sediment.
(D) Large part of sludge is pumped into anaerobic sludge digesters.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (C), (A), (D), (B)
(C) The effluent is passed into a settling tank where the bacterial ‘flocs’ are allowed to sediment — this comes first. After the BOD of the sewage has fallen, the flocs settle as a sediment called activated sludge.
(A) Small part of activated sludge is added into aeration tank — this comes second. This small part is pumped back and serves as the inoculum.
(D) Large part of sludge is pumped into anaerobic sludge digesters — this comes third. The rest of the sludge goes into large tanks where bacteria grow without oxygen.
(B) Anaerobic bacteria produces mixture of gases called biogas — this comes last. In the digesters the bacteria digest the sludge and give off methane, hydrogen sulphide and carbon dioxide. These gases form biogas.
NCERT Extract:
Microbes in Sewage Treatment – …
