Engineering Questions with Answers - Multiple Choice Questions
Environmental Engineering MCQ – Oxygen Sag Curve
1 - Question
What is yellow curve represents in the following figure?
Figure: Oxygen sag curve
a) Deoxygenation curve
b) Reoxygenation curve
c) Oxygen sag curve
d) Equilibrium concentration of oxygen
View Answer
Answer: a
Explanation: The yellow curve represents the deoxygenation curve, which depicts the depletion of dissolved oxygen in the absence of aeration.
2 - Question
Which of the following is represented by the green curve in the following figure?
Figure: Oxygen sag curve
a) Deoxygenation curve
b) Reoxygenation curve
c) Oxygen sag curve
d) Equilibrium concentration of oxygen
View Answer
Answer: b
Explanation: The green curve represents the reoxygenation curve, which depicts the supply of oxygen from the atmosphere to counterbalance the oxygen deficit.
3 - Question
The maximum deficiency of dissolved oxygen is represented by ____________
Figure: Oxygen sag curve
a) Dotted blue line
b) Green curve
c) Yellow curve
d) Violet curve
View Answer
Answer: a
Explanation: The maximum deficiency of dissolved oxygen is represented by the dotted blue line. It is finding with respect to the equilibrium concentration of oxygen.
4 - Question
Which of the following represents the oxygen sag curve in the following figure?
Figure: Oxygen sag curve
a) Dotted blue line
b) Green curve
c) Yellow curve
d) Red curve
View Answer
Answer: d
Explanation: The oxygen sag curve is represented by the red curve. It is also called as an oxygen deficit curve.
5 - Question
The oxygen deficit is maximum when?
Figure: Oxygen sag curve
a) Rate of reaeration is 0
b) Rate of deoxygenation is 0
c) Rate of reaeration equals the rate of deoxygenation
d) Rate of reaeration > rate of deoxygenation
View Answer
Answer: c
Explanation: The rate of oxygen deficit is the sum of the rate of reaeration and the rate of deoxygenation and it is maximum when the rate of reaeration equals the rate of deoxygenation.
6 - Question
When the BOD of wastewater increases, then?
Figure: Oxygen sag curve
a) Rate of reaeration decreases
b) Rate of oxygen deficit increases
c) Rate of oxygen deficit decreases
d) Amount of oxygen in wastewater increases
View Answer
Answer: b
Explanation: When the BOD of wastewater increases, the amount of dissolved oxygen decreases, so the rate of oxygen deficit increases.
7 - Question
Rate of aeration is independent of the D.O content of wastewater.
Figure: Oxygen sag curve
a) True
b) False
View Answer
Answer: b
Explanation: Rate of aeration = -(Rate of dissolved oxygen in water) which implies that the rate of aeration increases with increase in reduction of dissolved oxygen from wastewater.
8 - Question
The reoxygenation constant at temperature ‘T’ is expressed by ___________
a) KRT = KR20 (1.016)T
b) KRT = KR20 (1.047) T-20
c) KRT = KR20 (1.016)T-20
d) KRT = KR20 (1.047)T
View Answer
Answer: c
Explanation: The reoxygenation constant at temperature ‘T’,
KRT = KR20 (1.016)T-20, where KR20 is the reoxygenation constant at 20oC.