Waste Water Engineering

71. For sewers, inverted siphon is provided for

1. One pipe
2. Two pipes
3. Three pipes
4. Four pipes

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72. For the COD test of sewage, organic matter is oxidised by K₂Cr₂O₇ in the presence of

1. H₂SO₄
2. HNO₃
3. HCl
4. None of these

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73. For the survival of fish in a river stream, the minimum dissolved oxygen is prescribed

1. 3 ppm
2. 4 ppm
3. 5 ppm
4. 10 ppm

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74. For treating the sewage of a large city, you will recommend

1. A sedimentation tank and an activated sludge treatment plant
2. A plant consisting of Imhoff tanks with low rate trickling filters
3. Sedimentation tanks with high rate trickling filters
4. None of these

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75. For trunk and out-fall, the type of sewers generally used, is

1. Standard egg shaped
2. Circular shaped
3. Horse shoe shaped
4. Parabolic shaped

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76. For trunk sewers more than 1.25 m in diameter, the ratio of the maximum daily sewage flow to the average daily sewage flow is assumed

1. 1.5
2. 2
3. 2.5
4. 3

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77. Fresh sewage is generally

1. Alkaline
2. Acidic
3. Highly decomposed
4. A source of objectionable odour

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78. Fresh sewage may become stale in

1. One hour
2. Two to three hours
3. Three to four hours
4. Six hours

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79. Hazen's formula V_s = 418 (G_S - G_w)d [(3T + 70)/100] is used for the settlement velocity of the particles of diameter

1. Less than 0.01 mm
2. Less than 0.05 mm
3. Less than 0.1 mm
4. Greater than 0.1 mm

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80. House connections to the laterals is generally made by

1. R.C.C.
2. P.C.C.
3. Cast iron
4. Glazed stonewares

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