91. If the time of concentration is 9 minutes, then the intensity of rainfall according to British Ministry of Health formula will be
a) 4 mm/hr
b) lOmm/hr
c) 20 mm/hr
d) 40 mm/hr
Ans:d
92. The time of concentration is defined as
a) the time taken by rainfall water to run from most distant point of water shed to the inlet of sewer
b) the time required for flow of water in sewer to the point under consideration
c) sum of (a) and (b)
d) difference of (a) and (b)
Ans:c
93. The specific gravity of sewage is
a) much greater than 1
b) slightly less than 1
c) equal to 1
d) slightly greater than 1
Ans:d
94. The self cleansing velocity for all sewers in India is usually
a) less than 1.0 m/sec
b) 1.0 m/sec to 1.2 m/sec
c) 1.5 m/sec to 2.0 m/sec
d) 3.0 m/sec to 3.5 m/sec
Ans:b
95. The slope of sewer shall be
a) given in the direction of natural slope of ground
b) given in the direction opposite to natural slope of ground
c) zero
d) steeper than 1 in 20
Ans:a
96. The design discharge for the separate sewer system shall be taken as
a) equal to dry weather flow (DWF)
b) 2xDWF
c) 3 x DWF
d) 6xDWF
Ans:d
97. The design discharge for the combined sewer system shall be taken as
a) equal to rainfall
b) rainfall + DWF
c) rainfall + 2 DWF
d) rainfall + 6 DWF
Ans:c
98. The minimum and maximum diameters of sewers shall preferably be
a) 15 cm and 100 cm
b) 15 cm and 300 cm
c) 30 cm and 450 cm
d) 60 cm and 300cm
Ans:b
99. The main disadvantage of cement concrete sewers is
a) less strength
b) difficulty in construction
c) difficulty in transportation due to heavy weight
d) less life
Ans:c
100. Most suitable section of sewer in separate sewage system is
a) rectangular section
b) circular section
c) standard form of egg shaped sewer
d) modified egg shaped section
Ans:b
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 nof 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 remain-ing ,
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
126. Laying of sewers is usually done with the help of
a) a theodolite
b) a compass
c) sight rails and boning rods
d) a plane table
Ans:c
127. Corrosion in concrete sewers is caused by
a) septic conditions
b) dissolved oxygen
c) chlorine
d) nitrogen
Ans:a
128. If the sewage contains grease and fatty oils, these are removed in
a) grit chambers
b) detritus tanks
c) skimming tanks
d) sedimentation tanks
Ans:c
129. Generally the detention period for grit chambers is kept as
a) 1 minute
b) 5 minutes
c) 2-4 hours
d) 12 hours
Ans:a
130. Which of the following unit works in anaerobic conditions?
a) sludge digestion tank
b) sedimentation tank
c) activated sludge treatment
d) trickling filters
Ans:a
131. Septic tank is a
i) settling tank
ii) digestion tank
iii) aeration tank
The correct answer is
a) only (i)
b) (i) and (ii)
c) (i) and (iii)
d) only (iii)
Ans:b
132. The maximum efficiency of BOD removal is achieved in
a) oxidation pond
b) oxidation ditch
c) aerated lagoons
d) trickling filters
Ans:b
133. The working conditions in imhoff tanks are
a) aerobic only
b) anaerobic only
c) aerobic in lower compartment and anaerobic in upper compartment
d) anaerobic in lower compartment and aerobic in upper compartment
Ans:d
134. In facultative stabilization pond, the sewage is treated by
a) aerobic bacteria only
b) algae only
c) dual action of aerobic bacteria and anaerobic bacteria
d) sedimentation
Ans:c
135. The detention period for oxidation ponds is usually kept as
a) 4-8 hours
b) 24 hours
c) 10 to 15 days
d) 3 months
Ans:c
136. Composting and lagooning are the methods of
a) sludge digestion
b) sludge disposal
c) sedimentation
d) filtration
Ans:b
137. The main disadvantage of oxidation pond is that
a) large area is required for construction
b) maintenance and operation cost are high
c) BOD removal is very low
d) none of the above
Ans:a
138. For satisfactory working of a sludge digestion unit, the pH range of digested sludge should be maintained as
a) 4.5 to 6.0
b) 6.5 to 8.0
c) 8.5 to 10.0
d) 10.5 to 12.0
Ans:b
139. Sludge volume index is defined as the ratio of
a) percentage of sludge by volume to percentage of suspended solids by weight
b) percentage of sludge by volume to percentage of total solids by weight
c) percentage of suspended solids by weight to percentage of sludge by volume
d) percentage of total solids by weight to percentage of sludge by volume
Ans:a
140. For normal sludge, the value of sludge index for Indian conditions is
a) 0 to 50
b) 50 to 150
c) 150 to 350
d) 350 to 500
Ans:c
141. When there is no recirculation of sewage, then recirculation factor is
a) 0
b) 1
c) infinity
d) none of the above
Ans:b
142. For the same solid content, if the quantity of sludge with moisture content of 98% is X, then the quantity of sludge with moisture content of 96% will be
a) X/4
b) X/2
c) X
d) 2X
Ans:b
143. A pipe which is installed in the house drainage to preserve the water seal of traps is called
a) vent pipe
b) antisiphonage pipe
c) waste pipe
d) soil pipe
Ans:b
144. In the two-pipe system of house plumbing, the pipes required are
a) one soil pipe, one waste pipe and one vent pipe
b) one soil pipe, two waste pipes and one vent pipe
Ans:c
145. The pipe which is used to carry the discharge from sanitary fittings like bath rooms, kitchens etc. is called
a) waste pipe
b) soil pipe
c) vent pipe
d) antisiphonage pipe
Ans:a
146. The gas from sludge digestion tank is mainly composed of
a) nitrogen
b) carbon dioxide
c) hydrogen sulphide
d) methane
Ans:d
147. Most of the bacteria in sewage are
a) parasitic
b) saprophytic
c) pathogenic
d) anaerobic
Ans:b
148. The process of lagooning is primarily a means of
a) reducing the excessive flow in sewers
b) disposing of sludge
c) increasing the capacity of storage re-servoirs
d) increasing flow of sewage through imhoff tanks
Ans:b
149. The biochemical treatment of sewage effluents is essentially a process of
a) oxidation
b) dehydration
c) reduction
d) alkalinization
Ans:a
150. To divert excessive flow from combined sewers, the most commonly used weir is a
a) cipoletti weir
b) broadcrested weir
c) leaping weir
d) submerged weir
Ans:c
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a) 4 mm/hr
b) lOmm/hr
c) 20 mm/hr
d) 40 mm/hr
Ans:d
92. The time of concentration is defined as
a) the time taken by rainfall water to run from most distant point of water shed to the inlet of sewer
b) the time required for flow of water in sewer to the point under consideration
c) sum of (a) and (b)
d) difference of (a) and (b)
Ans:c
93. The specific gravity of sewage is
a) much greater than 1
b) slightly less than 1
c) equal to 1
d) slightly greater than 1
Ans:d
94. The self cleansing velocity for all sewers in India is usually
a) less than 1.0 m/sec
b) 1.0 m/sec to 1.2 m/sec
c) 1.5 m/sec to 2.0 m/sec
d) 3.0 m/sec to 3.5 m/sec
Ans:b
95. The slope of sewer shall be
a) given in the direction of natural slope of ground
b) given in the direction opposite to natural slope of ground
c) zero
d) steeper than 1 in 20
Ans:a
96. The design discharge for the separate sewer system shall be taken as
a) equal to dry weather flow (DWF)
b) 2xDWF
c) 3 x DWF
d) 6xDWF
Ans:d
97. The design discharge for the combined sewer system shall be taken as
a) equal to rainfall
b) rainfall + DWF
c) rainfall + 2 DWF
d) rainfall + 6 DWF
Ans:c
98. The minimum and maximum diameters of sewers shall preferably be
a) 15 cm and 100 cm
b) 15 cm and 300 cm
c) 30 cm and 450 cm
d) 60 cm and 300cm
Ans:b
99. The main disadvantage of cement concrete sewers is
a) less strength
b) difficulty in construction
c) difficulty in transportation due to heavy weight
d) less life
Ans:c
100. Most suitable section of sewer in separate sewage system is
a) rectangular section
b) circular section
c) standard form of egg shaped sewer
d) modified egg shaped section
Ans:b
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 nof 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 remain-ing ,
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
126. Laying of sewers is usually done with the help of
a) a theodolite
b) a compass
c) sight rails and boning rods
d) a plane table
Ans:c
127. Corrosion in concrete sewers is caused by
a) septic conditions
b) dissolved oxygen
c) chlorine
d) nitrogen
Ans:a
128. If the sewage contains grease and fatty oils, these are removed in
a) grit chambers
b) detritus tanks
c) skimming tanks
d) sedimentation tanks
Ans:c
129. Generally the detention period for grit chambers is kept as
a) 1 minute
b) 5 minutes
c) 2-4 hours
d) 12 hours
Ans:a
130. Which of the following unit works in anaerobic conditions?
a) sludge digestion tank
b) sedimentation tank
c) activated sludge treatment
d) trickling filters
Ans:a
131. Septic tank is a
i) settling tank
ii) digestion tank
iii) aeration tank
The correct answer is
a) only (i)
b) (i) and (ii)
c) (i) and (iii)
d) only (iii)
Ans:b
132. The maximum efficiency of BOD removal is achieved in
a) oxidation pond
b) oxidation ditch
c) aerated lagoons
d) trickling filters
Ans:b
133. The working conditions in imhoff tanks are
a) aerobic only
b) anaerobic only
c) aerobic in lower compartment and anaerobic in upper compartment
d) anaerobic in lower compartment and aerobic in upper compartment
Ans:d
134. In facultative stabilization pond, the sewage is treated by
a) aerobic bacteria only
b) algae only
c) dual action of aerobic bacteria and anaerobic bacteria
d) sedimentation
Ans:c
135. The detention period for oxidation ponds is usually kept as
a) 4-8 hours
b) 24 hours
c) 10 to 15 days
d) 3 months
Ans:c
136. Composting and lagooning are the methods of
a) sludge digestion
b) sludge disposal
c) sedimentation
d) filtration
Ans:b
137. The main disadvantage of oxidation pond is that
a) large area is required for construction
b) maintenance and operation cost are high
c) BOD removal is very low
d) none of the above
Ans:a
138. For satisfactory working of a sludge digestion unit, the pH range of digested sludge should be maintained as
a) 4.5 to 6.0
b) 6.5 to 8.0
c) 8.5 to 10.0
d) 10.5 to 12.0
Ans:b
139. Sludge volume index is defined as the ratio of
a) percentage of sludge by volume to percentage of suspended solids by weight
b) percentage of sludge by volume to percentage of total solids by weight
c) percentage of suspended solids by weight to percentage of sludge by volume
d) percentage of total solids by weight to percentage of sludge by volume
Ans:a
140. For normal sludge, the value of sludge index for Indian conditions is
a) 0 to 50
b) 50 to 150
c) 150 to 350
d) 350 to 500
Ans:c
141. When there is no recirculation of sewage, then recirculation factor is
a) 0
b) 1
c) infinity
d) none of the above
Ans:b
142. For the same solid content, if the quantity of sludge with moisture content of 98% is X, then the quantity of sludge with moisture content of 96% will be
a) X/4
b) X/2
c) X
d) 2X
Ans:b
143. A pipe which is installed in the house drainage to preserve the water seal of traps is called
a) vent pipe
b) antisiphonage pipe
c) waste pipe
d) soil pipe
Ans:b
144. In the two-pipe system of house plumbing, the pipes required are
a) one soil pipe, one waste pipe and one vent pipe
b) one soil pipe, two waste pipes and one vent pipe
Ans:c
145. The pipe which is used to carry the discharge from sanitary fittings like bath rooms, kitchens etc. is called
a) waste pipe
b) soil pipe
c) vent pipe
d) antisiphonage pipe
Ans:a
146. The gas from sludge digestion tank is mainly composed of
a) nitrogen
b) carbon dioxide
c) hydrogen sulphide
d) methane
Ans:d
147. Most of the bacteria in sewage are
a) parasitic
b) saprophytic
c) pathogenic
d) anaerobic
Ans:b
148. The process of lagooning is primarily a means of
a) reducing the excessive flow in sewers
b) disposing of sludge
c) increasing the capacity of storage re-servoirs
d) increasing flow of sewage through imhoff tanks
Ans:b
149. The biochemical treatment of sewage effluents is essentially a process of
a) oxidation
b) dehydration
c) reduction
d) alkalinization
Ans:a
150. To divert excessive flow from combined sewers, the most commonly used weir is a
a) cipoletti weir
b) broadcrested weir
c) leaping weir
d) submerged weir
Ans:c
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