# Environmental Engineering Questions and Answers – Racks and Screen

This set of Environmental Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Racks and Screen”.

1. The minimum spacing between the bars on fine screen is ____________
a) 0.3mm
b) 0.9mm
c) 1.5mm
d) 0.5mm

Explanation: The range of space between the bars in fine screen is 1.5-3mm having minimum spacing as 1.5mm.

2. The spacing between the bars in racks is ____________
a) 30mm
b) 50mm
c) 70mm
d) 90mm

Explanation: The spacing between the bars in racks is 50mm. It is commonly called as coarse screen.

3. Screens are inclined to the direction of flow to ____________
a) Increase the flow velocity
b) Increase the opening area
c) Decrease the flow velocity

Explanation: Screens are inclined to the direction of flow to decrease the flow velocity in order to increase the efficiency of the screen.

4. The maximum spacing between the bars in medium screen is ____________
a) 40mm
b) 50mm
c) 70mm
d) 90mm

Explanation: The range of space between the bars in fine screen is 7-40mm having maximum spacing as 40mm.

5. __________ is used to cut the sewage into smaller parts.
a) Flocculator
b) Tube settlers
c) Shredders
d) Aerators

Explanation: Shredder is a device which is used to cut large size sewage particles into a smaller size. It is composed of screens and cutting teeth.
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6. What is the maximum capacity of medium screen in collecting solids?
a) 30L
b) 40L
c) 50L
d) 90L

Explanation: Medium screen can collect up to the maximum capacity of 90L of solids per 106 L of effluent.

7. The head loss through the screen is given by HL = k* (Vt2 – Va2), where Vt and Va are velocities through and above the screen respectively. What is the value of constant k?
a) 1
b) 0.0050
c) 0.0729
d) 0.0236

Explanation: The expression for the head loss through the screen is given by
HL = 0.0729* (Vt2 – Va2), where Vt and Va are the velocities through and above the screen respectively.

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