Engineering Questions with Answers - Multiple Choice Questions

Environmental Engineering MCQ – Diffused Air System

1 - Question

Which of the following is called as air diffusion method?
a) Activated sludge aeration
b) Diffused air aeration
c) Mechanical aeration
d) Combined aeration

View Answer

Answer: b
Explanation: Diffused air aeration method is also called as air diffusion method where diffused air aerators are used for diffusing the air in the aeration tank.




2 - Question

The maximum quantity of air required in diffused aerator is ______ m3 per million litres of sewage.
a) 4000
b) 5000
c) 6000
d) 8000

View Answer

Answer: d
Explanation: The minimum and maximum quantity of air required in diffused aerator is 6000 and 8000 m3 respectively per million litres of sewage.




3 - Question

The effective area of the diffuser plate used in the aeration tank is ___________
a) 400cm2
b) 780cm2
c) 1160cm2
d) 800cm2

View Answer

Answer: b
Explanation: Diffuser plates are provided at the bottom of the aeration tank. It is square in shape with the dimension of 30cm x 30cm.




4 - Question

The maximum depth of aeration tank used in activated sludge process is ___________
a) 1m
b) 2m
c) 4.5m
d) 5.5m

View Answer

Answer: c
Explanation: The depth of aeration tank lies between 3 to 4.5m and is 4-6m wide.




5 - Question

Which device is used in the aeration tank for cleaning purposes?
a) Diffuser plate
b) Paddles
c) Tube diffuser
d) Header pipe

View Answer

Answer: c
Explanation: Tube diffuser is suspended in the aeration tank and can be used for cleaning without emptying the tank.




6 - Question

With how much pressure the air is filled in the aeration tank?
a) 70-90kN/m2
b) 34-56kN/m2
c) 10-20kN/m2
d) 35-70kN/m2

View Answer

Answer: d
Explanation: The air is compressed in the diffused air aerator with the pressure of 35-70kN/m2 resulting in the formation of the bubbles, improving the efficiency of aeration.




7 - Question

The effective area of tube diffuser used in the aeration tank is ___________
a) 400cm2
b) 780cm2
c) 1160cm2
d) 800cm2

View Answer

Answer: c
Explanation: Tube diffuser is 60cm long tube having an internal diameter of 7.5cm and an effective area of 1160cm2.




8 - Question

With which device, the air is introduced in the aeration tank?
a) Diffuser plate
b) Paddles
c) Cone with spiral vanes
d) Header pipe

View Answer

Answer: a
Explanation: The air is introduced in the diffuser air aerators with the help of diffuser plates. It rotates and results in the formation of small bubbles causing aeration of sewage.

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