Arrange the following events in correct order pertaining to sewage treatment plant?
(A) Bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide.
(B) Primary effluent is passed into aeration tank for the growth of microbes into flocs.
(C) A small part of activated sludge is pumped back into aeration tank as inoculum and remaining to anaerobic sludge digesters.
(D) The bacteria and fungi in the sludge are digested by another kind of bacteria.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (B), (C), (D), (A)
(B) Primary effluent is passed into aeration tank for the growth of microbes into flocs. — first. Secondary treatment begins here. Air is pumped in, and aerobic microbes grow into flocs that eat up the organic matter, lowering the BOD.
(C) A small part of activated sludge is pumped back into aeration tank as inoculum and remaining to anaerobic sludge digesters. — second. The flocs settle in a tank as activated sludge. A little is sent back to seed the aeration tank, and the rest goes to the digesters.
(D) The bacteria and fungi in the sludge are digested by another kind of bacteria. — third. In the digesters, anaerobic bacteria digest the bacteria and fungi of the sludge.
(A) Bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. — last. This digestion gives out biogas, which can be used as fuel.
NCERT Extract:
Microbes in Sewage Treatment – …
