# Environmental Engineering Questions and Answers – Devices Associated with Sewer

This set of Environmental Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Devices Associated with Sewer”.

1. Which of the following is not a sewer appurtenance?
a) Storm regulator
b) Flushing tank
c) Water tank
d) Manholes

Explanation: Sewer appurtenance are the structures that are constructed for the efficient performance and maintenance of sewers. The water tank is not a sewer appurtenance.

2. ______ provides the working space for maintenance and inspection of sewers.
a) Lamp holes
b) Manholes
c) Flushing tanks
d) Working chamber

Explanation: Working chamber provides the working space for maintenance and inspection of sewers. It is situated at the lower part of the manhole.

3. The minimum thickness of the side wall of the manhole is __________
a) 50mm
b) 100mm
c) 225mm
d) 300mm

Explanation: The minimum thickness of the side wall of the manhole is 225mm and they are commonly made of bricks.

4. Which of the following is situated above the working chamber in a deep manhole?
a) Main sewer
b) Access shaft
c) Branch sewer
d) Channel

Explanation: The access shaft lies above the working chamber which is just below the manhole cover.

5. If the depth of excavation is 4m. What is the thickness of the brick wall of manhole?
a) 12cm
b) 16cm
c) 20cm
d) 26cm

Explanation: The thickness of brick wall of manhole (in cm) = 10 + 4*depth of excavation (in m) = 10 + 4*4 = 26cm.
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6. Into how many types manholes are classified on the basis of depth of manhole?
a) 3
b) 5
c) 6
d) 7

Explanation: Manholes are classified into Shallow, Normal and Deep on the basis of depth of the manhole.

7. The minimum diameter of the access shaft for a circular manhole is __________
a) 60cm
b) 20cm
c) 30cm
d) 10cm

Explanation: Access shaft is the upper portion of manhole whose minimum diameter for a circular manhole is 60cm.

8. The manhole in which inclined pipe for transfer of sewage from branch to main sewer is __________
a) Deep manhole
b) Ramp
c) Drop manhole
d) Normal manhole

Explanation: Ramp has an inclined pipe for the transfer of sewage which is used when the drop is less.

9. The thickness of the manhole frame is __________
a) 10cm
b) 15cm
c) 20cm
d) 40cm

Explanation: The manhole frame is made of cast iron having 10cm width and the thickness is 20cm.

10. The minimum diameter of the working chamber for a circular manhole is __________
a) 0.8m
b) 0.9m
c) 1m
d) 1.2m

Explanation: The working chamber is the lower portion of the manhole having a minimum diameter of 1.2 m.

11. The manhole in which vertical pipe is used for the transfer of sewage from branch to main sewer is __________
a) Deep manhole
b) Ramp
c) Drop manhole
d) Normal manhole

Explanation: Drop manholes are provided with vertical pipe so that the sewage does not fall on the people working at manhole.

12. Which sewer appurtenance allows lamp in the sewer?
a) Catch basin
b) Drop manhole
c) Lamp hole
d) Storm regulators

Explanation: The lamp hole is acting as an inspection device where lamps are inserted. It is used when the construction of manhole is difficult.

13. Which sewer appurtenance is used for removing rainwater from the roads?
a) Catch basin
b) Gullies
c) Lamp hole
d) Storm regulators

Explanation: Gullies are placed along the roadside at an interval of 30-60m to remove the rainwater from the road.

14. ________ removes oil and grease from the sewage.
a) Catch basin
b) Gullies
c) Grease and oil traps
d) Storm regulators

Explanation: The oil and grease sticks to the sides of the sewer and reduces the sewer capacity. So, it is essential to remove oil and grease, which can be done by the device called as Grease and oil traps.

15. Which device is used to prevent the clogging of sewer pipes?
a) Flushing tank
b) Drop manhole
c) Lamp hole
d) Storm regulators

Explanation: Flushing tank is used to flush and clean the sewer to prevent it from clogging. This is done either by automatic flushing tank or by hand operated flushing tank.

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