# Environmental Engineering Questions and Answers – Problems in Filter Operation

This set of Environmental Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Problems in Filter Operation”.

1. The loss of head during cleaning operation of a rapid sand filter is __________
a) 15-30cm
b) 1-5cm
c) 10-20cm
d) 10-25cm

Explanation: When cleaned bed is put into operation, the loss of head through it is 15-30cm and it goes on increasing as impurities are arrested in filter media.

2. The thickness of the suspended matter on top of the sand bed is __________
a) Directly proportional to head loss
b) Inversely proportional to head loss
c) Independent of the head loss
d) Directly proportional to the square of head loss

Explanation: As the thickness of suspended matter on top of the sand bed increases, the head loss is increased. So, it is directly proportional to head loss.

3. When the loss of the head exceeds the static head, the head becomes _____
a) Positive
b) Negative
c) Constant
d) Zero

Explanation: The head becomes negative when the loss of the head through the bed depth exceeds the static head. The negative head is the fall of liquid level in the piezometric tube below the center line of under drainage system.

4. What is the permissible negative head loss of a rapid sand filter?
a) 0.2-1m
b) 0.1-0.5m
c) 0.5-2m
d) 0.8-1.2m

Explanation: The permissible negative head loss of a rapid sand filter is 0.8-1.2m. When the permissible limits are reached, the filter run is terminated and the filter is back washed.

5. Which type of problem is caused in filter due to the accumulation of solids on the top surface of filter media?
a) Clogging
b) Air binding
c) Sand incrustation
d) Sand leakage

Explanation: Clogging of bed is caused due to the accumulation of solids on the top surface of filter media, which results in the formation of mud balls and cracking of the bed.
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6. ______ are formed in filters due to insufficient washing of sand grains.
a) Sand boils
b) Mud balls
c) Clogging
d) Bubbles

Explanation: Mud balls are formed in filters due to insufficient washing of sand grains. Mud accumulates on the sand surface and form a dense mat.

7. The cracking of bed is more prominent __________
a) Near the wall junction
b) Outside the wall junction
c) Inside the wall junction
d) On the wall junction

Explanation: The cracking of bed is more prominent near the wall junction which allows the dirty matter to penetrate into filter media which decreases the efficiency of filtration.

8. In which type of filtration problem, layers of gravel are displaced?
a) Clogging
b) Air binding
c) Sand incrustation
d) Sand leakage

Explanation: During Sand leakage, layers of gravel are displaced during back-washing. This can be minimized by proper proportioning of sand and gravel layers.

9. The tendency of jetting can be minimized by __________
a) Carbonating the water
b) Proportioning of layers of sand and gravel
c) Surface washing
d) Control of algae growth in the water

Explanation: The tendency of jetting can be minimized by surface washing. It can also be minimized by the use of an 8cm layer of coarse garnet between fine media and gravel.

10. _______ type of trouble in filter is caused by the released of dissolved air and gases from water.
a) Air binding
b) Clogging
c) Mud balls
d) Jetting

Explanation: Air binding is caused by the released of dissolved air and gases from water to form bubbles which occupy void space of the filter media and the drainage system.

11. How the problem of sand incrustation can be minimized?
a) Carbonating the water
b) Proportioning of layers of sand and gravel
c) Surface washing
d) Control of algae growth in the water

Explanation: The problem of sand incrustation can be minimized by carbonating the water so as to dissolve calcium carbonate that has deposited on sand grains.

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