Waste Water Engineering

91. If is the rugosity coefficient, 'r' is the hydraulic depth, 's' is the bed slope of sewer, the velocity of flow in m/sec may be obtained by the formula V = (1/n) r²/³ s1/2 evolved by

1. Chezy
2. Manning
3. Bazin
4. Kutter

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92. If q is the average sewage flow from a city of population P, the maximum sewage flow

1. Q = [(4 + )/(18 + )] q
2. Q = [(18 + P)/(4 + )] q
3. Q = [(18 + )/(4 + )] q
4. Q = [(5 + )/((15 + )] q

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93. If the depletion of oxygen is found to be 2.5 mg/litre after incubating 2.5 ml of sewage diluted to 250 ml for 5 days at 20°C, B.O.D. of the sewage is

1. 50 mg/l
2. 100 mg/l
3. 150 mg/l
4. 250 mg/l

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94. If the depletion of oxygen is found to be 5 ppm after incubating a 2.5% solution of sewage sample for 5 days at 21°C, B.O.D. of the sewage is

1. 50 ppm
2. 100 ppm
3. 150 ppm
4. 200 ppm

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95. If the depth of flow in a circular sewer is 1/4th of its diameter D, the wetted perimeter is

1. πD/2
2. πD/4
3. πD/3
4. πD

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96. If the depth of partial flow in a sewer of diameter 2 m, is 50 cm, its wetted perimeter is

1. π
2. π/2
3. π/3
4. π2/3

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97. If the diameter of a sewer is 100 mm, the gradient required for generating self cleansing velocity is

1. 1 in 60
2. 1 in 100
3. 1 in 120
4. None of these

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98. If the diameter of a sewer is 150 mm, the gradient required for generating self cleansing velocity, is

1. 1 in 60
2. 1 in 100
3. 1 in 120
4. None of these

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99. If the diameter of sewer is 225 mm, the gradient required for generating self cleansing velocity, is

1. 1 in 60
2. 1 in 100
3. 1 in 120
4. None of these

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100. If the discharge of a sewer running half is 628 1.p.s., i = 0.001, and n = 0.010, the diameter of the sewer, is

1. 1.39 m
2. 1.49 m
3. 1.59 m
4. 1.69 m

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