# Waste Water Engineering Questions and Answers – Disc Filtration – 2

This set of Waste Water Engineering Questions and Answers for Aptitude test focuses on “Disc Filtration – 2”.

1. What is the size of openings for a disc filter?
a) 20-35 µm
b) 10-20 µm
c) 20-30 µm
d) 5-10 µm

Explanation: The size of the opening for a disc filter is 20-35 µm. The disc filter removes suspended solids. During normal operation, 60-70% of the disc filter is submerged.

2. What is the hydraulic loading rate in m2/m3/h of a disc filter assumed while designing it?
a) 0.25-0.83
b) 0.02-0.083
c) 2.5-8.3
d) 8.3-10

Explanation: The hydraulic loading rate of a disc filter assumed while designing it is 0.25-0.83 m2/m3/h. This is measured in the units m2/m3/h. This depends on the suspended solids present in the waste water.

3. What is the head loss considered for the disc filter while designing it?
a) 75-150 mm
b) 40-70 mm
c) 150-175 mm
d) 175-200 mm

Explanation: The head loss considered for the disc filter while designing it is 75-150 mm. This is based on the submerged surface area of the disc. In most cases, it is considered as 100 mm.

4. What is the drum diameter considered while designing the disc filter?
a) 0.75-1.5 m
b) 2-3 m
c) 3-4 m
d) 4-5 m

Explanation: The drum diameter considered while designing the filter is 0.75-1.5 m. This varies depending on screen design. Smaller diameter results in greater time for backwash.

5. What is the drum speed considered while designing a disc filter?
a) 1.8 m/ min
b) 1 m/min
c) 6 m/min
d) 4.5 m/min

Explanation: The drum speed considered while designing a disc filter is 4.5 m/min. This however varies with the head loss. This holds good at 50mm head loss.
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6. What is the drum speed considered while designing a disc filter at 150 mm head loss?
a) 30-40 m/min
b) 26 m/min
c) 20-25 m/min
d) 28 m/min

Explanation: The drum speed considered while designing a disc filter is 30-40 m/min. This however varies with the head loss. This holds good at 150mm head loss.

7. What is the hydraulic loading rate in m2/m3/h of a cloth disc filter assumed while designing it?
a) 0.1-0.27
b) 10-20
c) 2-4
d) 1-2

Explanation: The hydraulic loading rate of a cloth disc filter assumed while designing it is 0.1-0. 27 m2/m3/h. This is measured in. This depends on the suspended solids present in the waste water.

8. What is the head loss considered for the cloth disc filter while designing it?
a) 50-300 mm
b) 400-500 mm
c) 500 -600 mm
d) 600-700 mm

Explanation: The head loss considered for the cloth disc filter while designing it is 50-300 mm. This is based on the submerged surface area of the disc. In most cases, it is considered as 150-200 mm.

9. What is the drum diameter considered while designing the cloth disc filter?
a) 0.9-1.8 m
b) 2 m
c) 3-4 m
d) 5 m

Explanation: The drum diameter considered while designing the cloth filter is 0.9-1.8 m. This varies depending on screen design. Smaller diameter results in greater time for backwash.

10. What is the maximum NTU a disc filter can handle?
a) 25 NTU
b) 10 NTU
c) 50 NTU
d) 100 NTU

Explanation: The maximum NTU a disc filter can handle is 25 NTU. The removal efficiency is around 60-70%. This depends on the influent characteristics of the wastewater.

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