| Consider the following statements with reference to the procedures used in sewage water treatment |
| 1. The greater the Biological Oxygen Demand (BOD) of wastewater, more is its polluting potential. |
| 2. In the secondary treatment of sewage water, floes or masses of bacteria is allowed to grow and increase BOD levels. |
| 3. BOD refers to the amount of the oxygen that would be consumed if all the organic matter in 1 litre of water were oxidised by bacteria. |
| Which of the statements] given above is/are incorrect? |
A) 1 and 2
B) 1 and 3
C) Only 2
D) (d) All of these
Correct Answer: C
Solution :
[c] The secondary treatment of sewage water allows vigorous growth of useful aerobic microbes into floes (masses of bacteria associated with fungal filaments to form mesh like structures). While growing, these microbes consume the major part of the organic matter in the effluent. This significantly reduces the BOD (Biochemical Oxygen Demand) of the effluent.
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