A. starch iodide method
B. orthotolidine method
C. both (A) and (B)
D. none of the above
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If the total hardness of water is greater than its total alkalinity, the carbonate hardness will be equal to________________?
0
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The dissolved oxygen level in natural unpolluted waters at normal temperature is found to be of the order of________________?
A. total alkalinity
B. total hardness
C. total hardness – total alkalinity
D. non carbonate hardness
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The length of rectangular sedimentation tank should not be more than_______________?
A. 1 mg/litre
B. 10 mg/litre
C. 100 mg/litre
D. 1000 mg/litre
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Percentage of bacterial load that can be removed from water by the process of plain sedimentation is about_______________?
A. B
B. 2B
C. 4B
D. 8B
where B is the width of the tank
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The settling velocity of a particle in a sedimentation tank increases if______________?
A. 10 to 25
B. 50
C. 75
D. 100
0
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The detention period and overflow rate respectively for plain sedimentation as compared to sedimentation with coagulation are generally_______________?
A. particle size is decreased
B. the surface area of tank is increased
C. the depth of tank is decreased
D. none of the above
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Alum as a coagulant is found to be most effective when pH range of water is______________?
A. less and more
B. less and less
C. more and less
D. more and more
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The alum, when added as a coagulant in water_______________?
A. 2 to 4
B. 4 to 6
C. 6 to 8
D. 8 to 10
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In water treatment, rapid gravity filters are adopted to remove_______________?
A. does not require alkalinity in water for flocculation
B. does not affect pH value of water
C. increases pH value of water
D. decreases pH value of water