Question 51 : The slow sand filter is able to remove ______ % of bacteria in water.
1. 90
2. 95
3. 98-99
4. 100
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Question 52 : The tendency of jetting can be minimized by
1. Carbonating the water
2. Proportioning of layers of sand and gravel
3. Surface washing
4. Control of algae growth in the water
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Question 53 : In which type of filtration problem, layers of gravel are displaced?
1. Clogging
2. Air binding
3. Sand incrustation
4. Sand leakage
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Question 54 : The area of the filter is 1500. What is the number of beds to be provided?
1. 1
2. 2
3. 3
4. 6
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Question 55 : Which of the following is the best filter in terms of rate of filtration?
1. Pressure filter
2. Rapid sand filter
3. Dual media filter
4. Mixed media filter
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Question 56 : How is the grain size distribution of sand in rapid sand filter?
1. Stratified
2. Unlayered
3. Layered with heaviest grains at the top
4. Layered with lightest grains at the top
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Question 57 : What is the color of the surface coating formed during the filtration process?
1. White
2. Brown
3. Green
4. Reddish brown
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Question 58 : The minimum depth of sand of a rapid sand filter is given by
1. Stokes formula
2. Clark's formula
3. Hudson formula
4. Emden formula
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Question 59 : The thickness of the base material of a rapid sand filter on which filter media are supported is
1. 45-60cm
2. 20-80cm
3. 30-75cm
4. 10-30cm
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Question 60 : Which material is provided for the up flow bed in dual media bi-flow filter?
1. Anthracite
2. Sand
3. Rice husk
4. Graphite
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