What happens in anaerobic sludge digester?
(A) Anaerobic bacteria digest the bacteria and fungi in the sludge
(B) Aerobic bacteria digest the bacteria and fungi in the sludge
(C) Methane and Carbon dioxide is produced
(D) Methane and Nitrogen dioxide is produced
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A) and (C)
(A) Anaerobic bacteria digest the bacteria and fungi in the sludge — True.
(B) Aerobic bacteria digest the bacteria and fungi in the sludge — False. The digester is anaerobic.
(C) Methane and Carbon dioxide is produced — True. Along with hydrogen sulphide; together they form biogas.
(D) Methane and Nitrogen dioxide is produced — False. Nitrogen dioxide is not produced.
NCERT Extract:
Microbes in Sewage Treatment – “… Once the BOD 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. Here, other kinds of bacteria, which grow anaerobically, digest the bacteria and the fungi in the sludge. During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases form biogas and can be used as source of energy as it is inflammable.”