Environmental Chemistry - Result Question 12
####12. Water samples with $BOD$ values of $4 ppm$ and $18 ppm$, respectively, are
(2019 Main, 12 Jan I)
(a) clean and clean
(b) highly polluted and clean
(c) highly polluted and highly polluted
(d) clean and highly polluted
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Answer:
Correct Answer: 12. (d)
Solution:
- The amount of oxygen required by bacteria to break down the organic matter present in a certain value of a sample of water is called biochemical oxygen demand (BOD). The amount of BOD in the water is a measure of the amount of organic material in the water, in terms of how much oxygen will be required to break it down biologically. Clean water would have BOD value of less than $5 ppm$ whereas highly polluted water would have BOD value of $17 ppm$ or more.
BOD value of clean water $=4 ppm$
BOD value of highly polluted water $=18 ppm$
