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Environmental Issues — BIOLOGY STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceBIOLOGYEnvironmental Issues3 Marks
Question
What is the difference between biological oxygen demand and chemical oxygen demand? What is the effect of a higher biological oxygen demand on the level of dissolved oxygen and sensitive organisms in a water body?
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Answer

S. No.
Biological Oxygen Demand (BOD)
Chemical Oxygen Demand (COD)
(i)
It is the amount of oxygen required for microbial breakdown of organic matter.
It is the amount of oxygen required for oxidation of both biodegradable and non-biodegradable organic matter in the water.
(ii)
Its value is less than COD.
Its value is more than BOD.
Higher biological oxygen demand shows that the dissolved oxygen in water bodies is much reduced and thus aquatic animals will die.

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