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