Apr 7, 20202 min
Updated: Apr 26, 2020
101. Most suitable section of sewer in separate sewage system is circular section
102. An egg shaped section of sewer provides self cleansing velocity at
low discharges
103. The velocity of flow does not depend on length of sewer
104. The hydraulic!mean depth (HMD) for an egg-shaped sewer flowing two-third full is greater than HMD when flowing full
105. The effect of increasing diameter of sewer on the self cleansing velocity is
to increase it
106. The most commonly used sewer under culverts is circular brick sewer
107. The type of sewer which is suitable for both combined and separate system is
egg shaped sewer
108. The characteristics of fresh and septic sewage respectively are alkaline and acidic
109. The pathogens can be killed by chlorination
110. Which of the following retards the self purification of stream ? none
111. Sewage treatment units are normally designed for 15-20 years
112. Settling velocity increases With depth of tank
113. Standard BOD is measured at 20°C - 5 day
114. The correct relation between theoretical oxygen demand (TOD), Biochemical
oxygen demand (BOD) and Chemical oxygen demand (COD) is given by
TOD>COD>BOD
115. 5 day BOD is less than 4 day BOD keeping other conditions same
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
117. The rate of BOD exerted at any time is directly proportional to BOD remaining
118. The ratio of 5 day BOD to ultimate BOD is about 2/3
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
120. The minimum dissolved oxygen which should always be present in water in order to save the aquatic life is 4 ppm