1. What is the color of the surface coating formed during the filtration process?
a) White
b) Brown
c) Green
d) Reddish brown
Explanation: The surface coating is formed by the reddish brown deposit of partially decomposed organic matter together with Iron, Alumina, Manganese and Silica.
2. In the ________ zone of purification in filter media, bacteria oxidizes the organic matter completely.
a) Autotrophic
b) Heterotrophic
c) Schmutzdecke
d) Electrolytic
Explanation: In Heterotrophic zone, bacteria multiplies in large number, breaks down not only the organic matter but also destroys each other to maintain a balance of life in the filter.
3. The filtration rate of a slow sand filter is _____ litres of water per square metre.
a) 20
b) 30
c) 50
d) 100
Explanation: The surface area of the slow sand filter lies between 50m2 to 1000m2 and its filtration rate lies between 100 to 200 litres of water per m2.
4. Identify the correct statement from the following options.
a) Rapid sand filter has a high initial cost
b) Coagulation is essential in slow sand filter
c) Slow sand filter requires skilled supervision
d) Period of cleaning of Rapid sand filter is 1-2 days
Explanation: Rapid sand filter is cheap and economical and its period of cleaning is 1-2 days. Neither the coagulation nor the skilled supervision is required in the slow sand filter.
5. 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
Explanation: Sand, Anthracite and Garnet sand are used as a filter material but crushed rock is not used in the treatment of water.
6. 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
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
7. 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
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
8. The uniformity characteristics of sand expressed in terms of __________
a) Effective size
b) Effective size and uniformity coefficient
c) Uniformity coefficient
d) Mean velocity
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.
9. ____ 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
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.
10. 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
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.