1. The effective size of sand of the slow sand filter is __________
a) 0.1-0.2mm
b) 0.2-0.3mm
c) 0.4-0.7mm
d) 1-2mm
Explanation: The effective size of sand of the slow sand filter is 0.2-0.3mm and for rapid sand filter, the effective size is 0.4-0.7mm.
2. What is the value of specific gravity of sand filter?
a) 2
b) 2.6
c) 3.1
d) 3.5
Explanation: The specific gravity of sand filter lies in the range of 2.55-2.65. So, the value 2.6 lies in the range of specific gravity of sand filter
3. The value of uniformity coefficient for uniformly graded sand is ______
a) 0
b) 1
c) 10
d) 100
Explanation: Uniformity coefficient CU = D60/D10
For uniformly graded sand, CU = 1
So, D60 = D10
4. The value of specific gravity for Garnet sand is ____
a) 2.1
b) 3.6
c) 4.2
d) 5.1
Explanation: Garnet sand is a dense material with a specific gravity of 4.2 and is used as a constituent in mixed media filter. It is a costlier filter material.
5. Which of the following statement is correct?
a) Ignition loss of filter should not exceed 3%
b) Wearing loss of filter sand should not exceed 5%
c) The range of CU for the slow sand filter is 3-5
d) The range of CU for the rapid sand filter is 3-5
Explanation: The ignition loss of filter should not exceed 0.7%, wearing loss of filter sand should not exceed 3%, range of CU for the slow sand filter is 3-5 and for the rapid sand filter is between 1.3 and 1.7.
6. The depth of an enclosed tank of a slow sand filter lies in the range of ______
a) 1-2m
b) 2.5-4m
c) 2-5m
d) 3-5m
Explanation: The depth of an enclosed tank of a slow sand filter lies in the range of 2.5-4m and its surface area lies between 50-1000m2.
7. When the fineness of sand increases __________
a) The bacterial efficiency increases
b) The rate of filtration increases
c) The rate of filtration first decrease, then increase
d) The bacterial efficiency remains constant
Explanation: When the fineness of sand increases, the bacterial efficiency increases, but rate of filtration decreases. Fine sand is preferred when high bacteria and turbidity removal efficiency is desired.
8. The thickness of the base material on which filter media are supported is __________
a) 10-100cm
b) 20-80cm
c) 30-75cm
d) 10-30cm
Explanation: The base material consists of 30-75 cm thick gravel bed which is laid in layers of 15 cm with finer topmost layer and coarser bottom layer
9. The minimum number of filter beds in the slow sand filter is __________
a) 1
b) 2
c) 3
d) 5
Explanation: The minimum number of filter beds provided in the slow sand filter is 2 where one unit is provided as stand by for an area of 20m2
10.The area of the filter is 1500. What is the number of beds to be provided?
a) 1
b) 2
c) 3
d) 6
Explanation: The area of filter is 1500 which lies between 1201-2000m2. So, the number of beds to be provided is 6.