1. 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.
2. 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
3. ______ 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.
4. 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.
5. 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
6. 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
7. _______ 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.
8. 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
9. The head loss through the bed of solids of the filter can be determined by __________
a) Carmen-Kozney equation
b) Rose equation
c) Carmen-Kozney and Rose equation
d) Charles equation
Explanation: The head loss through the bed of solids of the filter can be determined by both Carmen-Kozney and Rose equation where two cases are considered, one for homogeneous mixed bed and other for stratified bed.
10. Which of the following has the highest shape factor as stated by Carmen?
a) Ottawa sand
b) Pulverized coal
c) Rounded coal
d) Angular sand
Explanation: The shape factor as stated by Carmen is 0.95 for Ottawa sand, 0.73 for pulverized coal and angular sand and 0.82 for rounded sand.