The polluting potential of waste water is determined by:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Biochemical oxygen demand
BOD (biochemical oxygen demand) is the amount of oxygen that would be used up if all the organic matter in one litre of water were oxidised by bacteria. It is an indirect measure of the organic matter present. The greater the BOD, the more polluting the water.
Option (1) Biochemical oxygen demand — Correct. BOD (biochemical oxygen demand) is the amount of oxygen consumed if all the organic matter in one litre of water were oxidised by bacteria. The greater the BOD, the more organic matter and the higher the polluting potential of the waste water.
Option (2) Presence of sludge — Incorrect. Sludge is the solid matter settled out during treatment; it is not a measure of pollution.
Option (3) Biogas production — Incorrect. Biogas is made from sludge in the digesters; it is a product of treatment.
Option (4) Flocs formation — Incorrect. Flocs are masses of bacteria and fungi that grow in the aeration tank and eat up the organic matter.
NCERT Extract:
Microbes in Sewage Treatment – …
