101. An egg shaped section of sewer
a) is economical than circular section
b) provides self cleansing velocity at low discharges
c) is more stable than circular section
d) is easy to construct
Ans:b
102. The velocity of flow does not depend on
a) grade of sewer
b) length of sewer
c) hydraulic mean depth of sewer
d) roughness of sewer
Ans:b
103. The hydraulic mean depth (HMD) for an egg-shaped sewer flowing two-third full is
a) equal to HMD when flowing full
b) less than HMD when flowing full
c) greater than HMD when flowing full
d) none of the above
Ans:c
104. The effect of increasing diameter of sewer on the self cleansing velocity is
a) to decrease it
b) to increase it
c) fluctuating
d) nil
Ans:b
105. The most commonly used sewer under culverts is
a) circular brick sewer
b) circular cast iron sewer
c) semi-elliptical sewer
d) horse-shoe type sewer
Ans:a
106. The type of sewer which is suitable for both combined and separate system is
a) circular sewer
b) egg shaped sewer
c) horse-shoe type sewer
d) semi-elliptical sewer
Ans:b
107. The characteristics of fresh and septic sewage respectively are
a) acidic and alkaline
b) alkaline and acidic
c) both acidic
d) both alkaline
Ans:b
108. The pathogens can be killed by
a) nitrification
b) chlorination
c) oxidation
d) none of the above
Ans:b
109. Which of the following retards the self purification of stream ?
a) higher temperature
b) sunlight
c) satisfying oxygen demand
d) none of the above
Ans:d
110. Sewage treatment units are normally designed for
a) 5-10 years
b) 15-20 years
c) 30-40 years
d) 40-50 years
Ans:b
111. Settling velocity increases with
a) specific gravity of solid particles
b) size of particles
c) depth of tank
d) temperature of liquid
Ans:c
112. Standard BOD is measured at
a) 20°C – 1day
b) 25°C- 3day
c) 20°C – 5day
d) 30°C- 5day
Ans:c
113. The correct relation between theoretical oxygen demand (TOD), Biochemical oxygen demand (BOD) and Chemical oxygen demand (COD) is given by
a) TOD>BOD>COD
b) TOD>COD>BOD
c) BOD>COD>TOD
d) COD>BOD>TOD
Ans:b
114. Select the correct statement.
a) 5 day BOD is the ultimate BOD.
b) 5 day BOD is greater than 4 day BOD keeping other conditions same.
c) 5 day BOD is less than 4 day BOD keeping other conditions same.
d) BOD does not depend on time.
Ans:c
115. 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
a) 1000
b) 4000
c) 100000
d) 400000
Ans:d
116. The rate of BOD exerted at any time is
a) directly proportional to BOD satisfied
b) directly proportional to BOD remaining ,
c) inversely proportional to BOD satisfied
d) inversely proportional to BOD re-maining
Ans:b
117. The ratio of 5 day BOD to ultimate BOD is about
a) 1/3
b) 2/3
c) 3/4
d) 1.0
Ans:b
118. 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
a) 100 ppm
b) 200 ppm
c) 300 ppm
d) 400 ppm
Ans:b
119. The minimum dissolved oxygen which should always be present in water in order to save the aquatic life is
a) 1 ppm
b) 4 ppm
c) 10 ppm
d) 40 ppm
Ans:b
120. The relative stability of a sewage sample, whose dissolved oxygen is same as the total oxygen required to satisfy BOD, is
a) 1
b) 100
c) infinite
d) zero
Ans:b
121. Dissolved oxygen in streams is
a) maximum at noon
b) minimum at noon
c) maximum at midnight
d) same throughout the day
Ans:a
122. Facultative bacteria are able to work in
a) presence of oxygen only
b) absence of oxygen only
c) presence as well as in absence of oxygen
d) presence of water
Ans:c
123. The means of access for inspection and cleaning of sewer line is known as
a) inlet
b) manhole
c) drop manhole
d) catch basin
Ans:b
124. Sewerage system is designed for
a) maximum flow only
b) minimum flow only
c) average flow only
d) maximum and minimum flow
Ans:d
125. Sewage treatment units are designed for
a) maximum flow only
b) minimum flow only
c) average flow only
d) maximum and minimum flow
Ans:c