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Quiz 1
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Q.1
A rain sanitary sewer is constructed to carry
Sanitary sewage
Storm sewage
Surface water
Ground water
Q.2
The pressure exerted by
The sewage when running full from inside, is called internal pressure
The internal pressure if any, causes tensile stress in the pipe material
Pressure sewers are designed to be safe in tension
All the above
Q.3
Pick up the incorrect statement from the following for allowing workers to enter sewers
The particular manhole and one manhole on upstream and one manhole on downstream should remain open for 30 minutes
Proper tests for the presence of poisonous gases must be carried out
The men entering the manhole should be advised to smoke in the sewer
Warning signals should be erected
Q.4
For design purposes, the normal rate of infiltration of ground water into the sewer, is
500 litres/km/cm
1000 litres/km/cm
1500 litres/km/cm
2000 litres/km/cm
Q.5
If the peak discharge of a storm water drain (S.W. Drain) is expected to exceed 150 cumecs, the free board to be provided, is
100 cm
90 cm
80 cm
50 cm
Q.6
If q is the average sewage flow from a city of population P, the maximum sewage flow
Q = [(4 + )/(18 + )] q
Q = [(18 + P)/(4 + )] q
Q = [(18 + )/(4 + )] q
Q = [(5 + )/((15 + )] q
Q.7
Fresh sewage may become stale in
One hour
Two to three hours
Three to four hours
Six hours
Q.8
The grit and silt of the grit chambers, may not be used for
Raising low lying areas by dumping
Concreting
Both A and B
Neither A nor B
Q.9
In 1000 kg of sewage, the total solids approximate
0.5 to 1.0 kg
1 kg to 2.0 kg
5 kg to 7.5 kg
7.5 kg to 10 kg
Q.10
Pick up the incorrect statement from the following:
The process of decomposing the organic matter under controlled anaerobic conditions, is called sludge digestion
Sludge digestion is carried out in sludge tank
The gases produced in sludge digestion process, contain 75% carbon dioxide
The gases produced in sludge digestion process, contain 75% methane
Q.11
Pick up the correct statement from the following:
Turbidity is more in strong sewage
The black colour indicates septic sewage
The sewage omits offensive odours after four hours
All the above
Q.12
When drainage to sewage ratio is 20, the peak dry weather flow is
20% of the design discharge
Slightly less than 5% of the design discharge
Slightly more than 5% of the design discharge
None of these
Q.13
The sewerage system consists of
House sewer
Lateral sewer
Branch sewer
All of these
Q.14
The gradient of sewers depends upon
Velocity of flow
Diameter of the sewer
Discharge
All the above
Q.15
The laying of sewers is done with
Magnetic compass
Theodolite
Level
Clinometer
Q.16
Pick up the correct statement from the following:
The boning rod is used for checking the levels of the sewer inverts
Manhole covers are made circular for the convenience of the cleaning staff
A manhole is classified as shallow manhole if its depth is less than 0.9 m
All the above
Q.17
A safety lamp when inserted in the upper portion of a manhole causes flames. It indicates the presence of
Carbondioxide gas
Hydrogen sulphide gas
Methane gas
Petrol vapours
Q.18
Pick up the correct statement from the following:
The circular section of sewers provides maximum hydraulic mean depth
The circular sewers are provided for separate sewerage system
The circular sewers work efficiently if the sections run at least half full
All the above
Q.19
The sewer which received discharge from two or more main sewers, is known as
A trunk sewer
An outfall sewer
A main sewer
An intercepting sewer
Q.20
Imhoff cone is used to measure
Total organic solids
Total solids
Total in organic solids
Settleable solids
Q.21
The normal values of over flow rates for secondary sedimentation tanks, ranges between
25,000 to 35,000 litres/sqm/day
40,000 to 50,000 litres/sqm/day
50,000 to 60,000 litres/sqm/day
80,000 to 10,000 litres/sqm/day
Q.22
The asbestos cement sewers are
Light in weight
Not structurally strong to bear large compressive stress
Susceptible to corrosion by sulphuric acid
All the above
Q.23
The normal value of over flow rates for plain primary sedimentation tanks, ranges between
25,000 to 35,000 litres/sqm/day
40,000 to 50,000 litres/sqm/day
50,000 to 60,000 litres/sqm/day
80,000 to 100,000 litres/sqm/day
Q.24
If D is the diameter of a circular sewer and D’ is the top horizontal diameter of an equivalent egg shaped section, the relationship which holds good, is
D’ = 0.64 D
D’ = 0.74 D
D’ = 0.84 D
D’ = 0.94 D
Q.25
hydraulically equivalent, the relationship which holds good, is
D8/3 = 4 b8/3
D3/8 = 4 b3/8
D2/3 = 4 b2/3
D3/2 = 4 b3/2
Q.26
For design of sewers, percentage of sewage discharge is assumed
65 to 70%
70 to 75%
75 to 80%
85%
Q.27
Nitrogen cycle of sewage, is
Liberation of ammonia-formation of nitrites-formation of nitrates-liberation of nitrogen
Liberation of nitrogen-liberation of ammonia-formation of nitrites- formation of nitrates
Liberation of nitrogen-formation of nitrates-formation of nitrites-liberation of ammonia
Formation of nitrates-formation of nitrites-liberation of nitrates-liberation of nitrates
Q.28
depends upon The Chezy’s constant C in the formula V = C
Size of the sewer
Shape of the sewer
Roughness of sewer surface
All the above
Q.29
The detention period for plain sedimentation water tanks, is usually
4 to 8 hours
8 to 16 hours
16 to 24 hours
24 to 36 hours
Q.30
The minimum recommended diameter of sewers, is
5 cm
10 cm
15 cm
20 cm
Q.31
Boussinesq’s equation for ascertaining unit pressure at a depth on sewers due to traffic loads, is
pt = 3H3p/2 Z5
pt = 2H3p/3 Z5
pt = 3H3p/2 Z5
pt = 2H3p/3 Z5
Q.32
Traps
Are water seals which prevent the entry of foul gases
Are used to trap the rats entering sewers
Dissolve the foul gases
Create symphonic action to increase the quick disposal of sewerage
Q.33
In sewage having fully oxidised organic matter, the nitrogen exists in the form of
Nitrites
Nitrates
Free ammonia
Aluminoid nitrogen
Q.34
In sewers the highest non-scouring velocity is achieved in
Glazed bricks sewers
Cast iron sewers
Cement concrete sewers
Stone ware sewers
Q.35
If the pH value of sewage is 7
It is acidic
It is alkaline
It is neutral
None of these
Q.36
Which one of the following tests is used for testing sewer pipes?
Water test
Ball test
Mirror test
All of these
Q.37
Pick up the correct statement from the following:
The larger the sewer in size, more will be velocity
The smaller the sewer in size, less will be velocity
The larger the sewer in size, no deposition will take place
The larger the sewer in size, deposition will take place
Q.38
Pick up the incorrect statement from the following:
The mixture of water and waste products, is called sewage
The treated sewage effluents, are generally used for irrigating the crops
The process of collecting, treating and disposing off the sewage, is called sewerage
The old convergence system was definitely better than water carried sewerage system
Q.39
In septic tanks, decomposition of organic bacteria, is done by
Anaerobic bacteria
Aerobic bacteria
Both types of bacterias
None of these
Q.40
Pick up the correct statement from the following:
Rate of digestion of sludge is more at higher temperature
Thermophilic organisms digest the sludge if the temperature ranges from 40° to 60°C
Mesophilic organisms digest the sludge if the temperature is between 25° and 40°C
All the above
Q.41
Pick up the incorrect statement from the following:
Septic tanks are horizontal continuous flow type of sedimentation tanks
Septic tanks are generally provided a detention period of 12 to 36 hours
Septic tanks are completely covered and high vent shafts are provided for the escape of foul gases
None of these
Q.42
Lead acetate test in sewer manhole is done to test the presence of
Methane gas
Hydrogen sulphide
Carbondioxide gas
Diesel vapours
Q.43
The sewers
Must be of adequate size to avoid over flow
Must flow under gravity ½ to ¾ full
Must be laid at least 2 to 3 m deep to collect /water from the basements
All the above
Q.44
The normal values of over flow rates for sedimentation tanks using coagulant, ranges between
25,000 to 35,000 litres/sqm/day
40,000 to 50,000 litres/sqm/day
50,000 to 60,000 litres/sqm/day
80,000 to 100,000 litres/sqm/day
Q.45
Aerobic activity is maximum
In freshly produced sewage
At sewer pipes
In sewer treatment plants
None of these
Q.46
During preliminary treatment of a sewage
Oil and grease are removed from skimming tanks
Floating materials are removed by screening
Girt and sand are removed by girt chambers
All the above
Q.47
The angle subtended by the surface of sewer water with partial flow, at sewer centre is 120°, the depth of sewerage is
20 cm
25 cm
40 cm
50 cm
Q.48
Primary treatment of sewage consists of removal of
Large suspended organic solids
Oil and grease
Sand and girt
Floating materials
Q.49
For efficient working of a sewer, it must be ensured that
Minimum velocity of 0.45 m/sec, is maintained at its minimum flow
A maximum velocity of 0.90 m/sec, is maintained at its maximum flow
Both (A) and (B)
Neither (A) nor (B)
Q.50
If the over land flow from the critical point to the drain is 8 km and the difference in level is 12.4 m, the inlet time is
2 hours
3 hours
4 hours
5 hours
0 h : 0 m : 1 s
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