Engineering Questions with Answers - Multiple Choice Questions

Environmental Engineering MCQ – Oxygen Demand

1 - Question

_____ is the amount of oxygen required to oxidize only organic matter in sewage.
a) Turbidity
b) BOD
c) COD
d) DO

View Answer

Answer: b
Explanation: BOD is the amount of oxygen required to oxidize only organic matter in sewage. It is always less than COD as COD oxidizes both organic and inorganic matter.




2 - Question

The full form of BOD is __________
a) Biodegradable oxygen demand
b) Biological oxygen demand
c) Biochemical oxygen demand
d) Bandwidth on demand

View Answer

Answer: c
Explanation: The full form of BOD is biochemical oxygen demand. It is measured in ppm or mg/L.




3 - Question

The biochemical oxygen demand is computed by __________
a) Dissolved oxygen / Dilution factor
b) Dissolved oxygen + Dilution factor
c) Dissolved oxygen – Dilution factor
d) Dissolved oxygen * Dilution factor

View Answer

Answer: d
Explanation: BOD = Dissolved oxygen * Dilution factor.
Where Dilution factor = Volume of diluted sewage sample / Volume of undiluted sewage sample.




4 - Question

The value of deoxygenation constant is independent of the temperature.
a) True
b) False

View Answer

Answer: b
Explanation: The value of deoxygenation constant is directly proportional to the temperature. It increases with increase in temperature.




5 - Question

Which of the following represents the first stage BOD in the following figure?
environmental-engineering-questions-answers-oxygen-demand-q5-to-q10
Figure: BOD vs time curve
a) ZR
b) RL
c) ZL
d) EP

View Answer

Answer: c
Explanation: ZL represents the first stage BOD from the given figure. The first stage BOD is also called as the carbonaceous demand.




6 - Question

 Which of the following represents the second stage BOD in the following figure?
environmental-engineering-questions-answers-oxygen-demand-q5-to-q10
Figure: BOD vs time curve
a) LP
b) RL
c) ZL
d) EP

View Answer

Answer: a
Explanation: LP represents the second stage BOD from the given figure. The second stage BOD is also called as the nitrogenous demand.




7 - Question

 The carbonaceous demand occurs due to oxidation of ______________
environmental-engineering-questions-answers-oxygen-demand-q5-to-q10
Figure: BOD vs time curve
a) Ammonia
b) Sulfur
c) Organic matter
d) Nitrogen

View Answer

Answer: c
Explanation: The carbonaceous demand occurs due to oxidation of organic matter. The carbonaceous demand is also called as the initial demand.




8 - Question

The nitrogenous demand occurs due to oxidation of ______________
environmental-engineering-questions-answers-oxygen-demand-q5-to-q10
Figure: BOD vs time curve
a) Ammonia
b) Sulfur
c) Organic matter
d) Nitrogen

View Answer

Answer: a
Explanation: The carbonaceous demand occurs due to oxidation of ammonia. The nitrogenous demand is also called as the final demand.




9 - Question

 Which of the following is correctly matched in the following figure?
environmental-engineering-questions-answers-oxygen-demand-q5-to-q10
Figure: BOD vs time curve
a) ZR – Carbonaceous demand
b) RE – Nitrogenous demand
c) EP – Final demand
d) ZP – Combined demand

View Answer

Answer: d
Explanation: ZP is correctly paired and it represents the combined demand, which includes both carbonaceous and nitrogenous demand.




10 - Question

 The nitrogenous demand begins after how many days?
environmental-engineering-questions-answers-oxygen-demand-q5-to-q10
Figure: BOD vs time curve
a) 1
b) 2
c) 3
d) 5

View Answer

Answer: d
Explanation: As the growth rate of nitrifying bacteria is slow, the nitrogenous demand begins after 5 days.

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