Environmental (101-120)

101. Most suitable section of sewer in separate sewage system is circular section

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102. An egg shaped section of sewer provides self cleansing velocity at

low discharges

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103. The velocity of flow does not depend on length of sewer

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104. The hydraulic!mean depth (HMD) for an egg-shaped sewer flowing two-third full is greater than HMD when flowing full

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105. The effect of increasing diameter of sewer on the self cleansing velocity is

to increase it

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106. The most commonly used sewer under culverts is circular brick sewer

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107. The type of sewer which is suitable for both combined and separate system is

egg shaped sewer

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108. The characteristics of fresh and septic sewage respectively are alkaline and acidic

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109. The pathogens can be killed by chlorination

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110. Which of the following retards the self purification of stream ? none

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111. Sewage treatment units are normally designed for 15-20 years

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112. Settling velocity increases With depth of tank

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113. Standard BOD is measured at 20°C - 5 day

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114. The correct relation between theoretical oxygen demand (TOD), Biochemical

oxygen demand (BOD) and Chemical oxygen demand (COD) is given by

TOD>COD>BOD

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115. 5 day BOD is less than 4 day BOD keeping other conditions same

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116. If Biochemical oxygen demand (BOD) of a town is 20000 kg/day and BOD per

capita per day is 0.05 kg, then population equivalent of town is 400000

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117. The rate of BOD exerted at any time is directly proportional to BOD remaining

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118. The ratio of 5 day BOD to ultimate BOD is about 2/3

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119. In a BOD test, 1.0 ml of raw sewage was diluted to 100 ml and the dissolved

oxygen concentration of diluted sample at the beginning was 6 ppm and it was 4 ppm at the end of 5 day incubation at 20°C. The BOD of raw sewage will be

200 ppm

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120. The minimum dissolved oxygen which should always be present in water in order to save the aquatic life is 4 ppm