This set of Environmental Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Filter Media”.
1. Which of the following is not commonly used as a filter material in the treatment of water?
a) Sand
b) Anthracite
c) Crushed rock
d) Garnet sand
View Answer
Explanation: Sand, Anthracite and Garnet sand are used as a filter material but crushed rock is not used in the treatment of water.
2. Which of the following is correct regarding the cheapest filter material used in water treatment?
a) Sand>Anthracite>Garnet sand
b) Sand<Anthracite>Garnet sand
c) Sand<Anthracite<Garnet sand
d) Sand=Anthracite>Garnet sand
View Answer
Explanation: Sand is the cheapest filter material followed by anthracite whereas Garnet sand is the costliest among them and is not used as a sole filter material but as a constituent in mixed media filter.
3. Consider the following statements regarding sand as filter material.
i. It should be free from clay or silt
ii. Organic matter should be present in the sand
iii. It should be nonuniform
Which of the above statement is/are correct?
a) i, ii
b) i only
c) ii, iii
d) i, ii, iii
View Answer
Explanation: Sand used as a filter material should be free from clay, silt, organic matter or other impurity. It should be uniform and of proper size.
4. The uniformity characteristics of sand expressed in terms of __________
a) Effective size
b) Effective size and uniformity coefficient
c) Uniformity coefficient
d) Mean velocity
View Answer
Explanation: The uniformity characteristics of sand are expressed in terms of effective size and uniformity coefficient. Effective size is called as effective diameter and uniformity coefficient is a measure of particle range.
5. ____ represents the size of sand particle such that 10% of particles are finer than this size.
a) D0.1
b) D1
c) D10
d) D100
View Answer
Explanation: D10 represents the size of sand particle such that 10% of particles are finer than this size. It is also called the effective size or effective diameter and is measured in mm.
6. What is CU in the expression CU= D60/D10 where D60 and D10 are the sizes of particle such that 60% and 10% of the particles are finer than these sizes respectively?
a) Coefficient of compaction
b) Coefficient of consolidation
c) Uniformity coefficient
d) Effective size
View Answer
Explanation: The uniformity coefficient is a measure of particle range and it is the ratio of D60 and D10 sizes. It is denoted by CU.
7. 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
View Answer
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.
8. What is the value of specific gravity of sand filter?
a) 2
b) 2.6
c) 3.1
d) 3.5
View Answer
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.
9. The value of uniformity coefficient for uniformly graded sand is ______
a) 0
b) 1
c) 10
d) 100
View Answer
Explanation: Uniformity coefficient CU = D60/D10
For uniformly graded sand, CU = 1
So, D60 = D10.
10. The value of specific gravity for Garnet sand is ____
a) 2.1
b) 3.6
c) 4.2
d) 5.1
View Answer
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.
11. 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
View Answer
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.
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