Question

Question 11: Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled A, B and C; but the laboratory attendant did not note which was which. The BOD values of the three samples A, B and C were recorded as 20mg/L, 8mg/L and 400mg/L, respectively. Which sample of the water is most polluted? Can you assign the correct label to each assuming the river water is relatively clean?

Class 12 - Biology - Microbes in Human Welfare Page 190

Answer 1

If water is more polluted it will have more BOD value . Out of the above three samples C is most polluted since it has the maximum value.
A is secondary effluent discharge from sewage treatment plant.
B is river water
C is untreated sewage water.
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