Environmental Engineering Multiple Choice Questions on “Diffused Air System”.
1. Which of the following is called as air diffusion method?
a) Activated sludge aeration
b) Diffused air aeration
c) Mechanical aeration
d) Combined aeration
Answer: b
Clarification: 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. The maximum quantity of air required in diffused aerator is ______ m3 per million litres of sewage.
a) 4000
b) 5000
c) 6000
d) 8000
Answer: d
Clarification: The minimum and maximum quantity of air required in diffused aerator is 6000 and 8000 m3 respectively per million litres of sewage.
3. The effective area of the diffuser plate used in the aeration tank is ___________
a) 400cm2
b) 780cm2
c) 1160cm2
d) 800cm2
Answer: b
Clarification: Diffuser plates are provided at the bottom of the aeration tank. It is square in shape with the dimension of 30cm x 30cm.
4. The maximum depth of aeration tank used in activated sludge process is ___________
a) 1m
b) 2m
c) 4.5m
d) 5.5m
Answer: c
Clarification: The depth of aeration tank lies between 3 to 4.5m and is 4-6m wide.
5. Which device is used in the aeration tank for cleaning purposes?
a) Diffuser plate
b) Paddles
c) Tube diffuser
d) Header pipe
Answer: c
Clarification: Tube diffuser is suspended in the aeration tank and can be used for cleaning without emptying the tank.
6. 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
Answer: d
Clarification: 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. The effective area of tube diffuser used in the aeration tank is ___________
a) 400cm2
b) 780cm2
c) 1160cm2
d) 800cm2
Answer: c
Clarification: Tube diffuser is 60cm long tube having an internal diameter of 7.5cm and an effective area of 1160cm2.
8. With which device, the air is introduced in the aeration tank?
a) Diffuser plate
b) Paddles
c) Cone with spiral vanes
d) Header pipe
Answer: a
Clarification: 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.