Engineering Questions with Answers - Multiple Choice Questions
Environmental Engineering MCQ’s – Mechanical Aeration System, Treatment of Sludge
1 - Question
The device used for the aeration in the combined aerator is ___________
a) Header pipe
b) Diffuser plate and paddles
c) Cone with spiral vanes
d) Diffuser plate
View Answer
Answer: b
Explanation: In combined aeration, both diffused air aeration and mechanical aeration take place using both diffuser plate and paddles.
2 - Question
The detention period of the Sheffield mechanical aeration tank is ___________
a) 15 hours
b) 1minute
c) 1 hour
d) 4 hours
View Answer
Answer: a
Explanation: The detention period of a Sheffield mechanical aeration tank is 15 hours. Its return sludge is 15-20% of sewage flow.
3 - Question
The minimum detention period of combined aerator is ___________
a) 1 hour
b) 2 hours
c) 3 hours
d) 4 hours
View Answer
Answer: c
Explanation: The detention period of combined aerator lies between 3 to 4 hours and the minimum detention period is 3 hours.
4 - Question
The speed at which the bubbles are formed in the simplex aerator?
a) 15rpm
b) 20rpm
c) 60rpm
d) 30rpm
View Answer
Answer: c
Explanation: The cones, with spiral vanes rotates at a high speed of 60rpm that results in the formation of bubbles in a simplex aerator resulting in the aeration of sewage.
5 - Question
Dorroco aerator is a type of ___________
a) Combined aerator
b) Mechanical aerator
c) Ridge and furrow type aerator
d) Spiral flow type aerator
View Answer
Answer: a
Explanation: Dorroco aerator is a type of combined aerator which is efficient in comparison to diffused air and mechanical aerator.
6 - Question
Simplex aerator is a type of ___________
a) Combined aerator
b) Mechanical aerator
c) Ridge and furrow type aerator
d) Spiral flow type aerator
View Answer
Answer: b
Explanation: Simplex aerator is a type of mechanical aerator where a square or rectangular tank with a hopper bottom is used.
7 - Question
Which gas is produced in aerobic digestion of sludge?
a) NO2
b) CO2
c) O2
d) H2S
View Answer
Answer: b
Explanation: Carbon dioxide gas is produced in the aerobic digestion of sludge by the oxidation of organic matter by bacteria into CO2.
8 - Question
Which of the following process is not involved in the treatment of sludge?
a) Dewatering
b) Drying
c) Flocculation
d) Conditioning
View Answer
Answer: c
Explanation: The process involved in the treatment of sludge are thickening, stabilization, dewatering and dying.
9 - Question
Which of the following is the final stage in the sludge treatment process?
a) Digestion
b) Dewatering
c) Drying
d) Thickening
View Answer
Answer: c
Explanation: Drying of the sludge is the final stage in the sludge treatment process where the most stable form of sludge is obtained.
10 - Question
In which sludge treatment process, the organic solids are converted into more stable form?
a) Dewatering
b) Thickening
c) Digestion
d) Conditioning
View Answer
Answer: c
Explanation: In the sludge digestion process, the organic solids are converted into more stable form. It makes the dewatering and drying process of sludge simpler.
11 - Question
The sludge treatment process to increase the solid content of sludge is ___________
a) Dewatering
b) Thickening
c) Conditioning
d) Drying
View Answer
Answer: b
Explanation: In sludge thickening, the solid content of sewage is increased by gravity flotation and clarifier.
12 - Question
The process of removal of water from the sludge is called ______
a) Dewatering
b) Thickening
c) Digestion
d) Drying
View Answer
Answer: a
Explanation: Dewatering is the process of removal of water from the sludge. It can be done by drying or subjected the sludge with pressure.
13 - Question
In which sludge treatment process, the sludge is treated with chemicals?
a) Dewatering
b) Thickening
c) Conditioning
d) Drying
View Answer
Answer: c
Explanation: In sludge conditioning, the sludge is treated with chemicals in order to separate the water from the sludge and improving the dewatering characteristics of the sludge.