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Question
(a) Three water samples A, B, C are collected. Their BOD was found to be 20mg/L, 8mg/L and 400mg/L respectively. Which sample is most polluted? Give reasons.
(b) At which stage of sewage treatment is BOD of effluent reduced? [3]
(b) At which stage of sewage treatment is BOD of effluent reduced? [3]
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Solution
(a) Sample C is the most polluted one. [1]
Reason - BOD is a measure of the organic matter present
in the water. The greater the BOD of waste water, more is its polluting potential. [1]
(b) BOD of effluent is reduced at the secondary treatment or biological treatment stage of sewage treatment. [1]
Reason - BOD is a measure of the organic matter present
in the water. The greater the BOD of waste water, more is its polluting potential. [1]
(b) BOD of effluent is reduced at the secondary treatment or biological treatment stage of sewage treatment. [1]
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