Engineering Questions with Answers - Multiple Choice Questions

Environmental Engineering MCQ – 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.

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