Question

In which one of the following, the BOD (Biochemical Oxygen Demand) of sewage (S), distillery effluent (DE), paper mill effluent (PE) and sugar mill effluent (SE) have been arranged in ascending order

• A. SE < S < PE < DE
• B. SE < PE < S < DE
• C. PE < S < SE < DE
• D. S < DE < PE < SE

Answer 1

The correct option is D S < DE < PE < SE

• Degradation of organic matter by microbes requires oxygen.
• Degree of impurity of water due to organic matter is measured in terms of biochemical oxygen demand or BOD.
• It is the oxygen required for the microorganisms to completely metabolize organic wastes.
• BOD is maximum for the distilleries and sugar industry.
  

So, option D is correct.