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Q.1
If the length of overland flow from the critical point to the mouth of drain is 13.58 km and difference in level between the critical point and drain mouth is 10 m, the inlet time is
2 hours
4 hours
6 hours
8 hours
Q.2
If the diameter of a sewer is 150 mm, the gradient required for generating self cleansing velocity, is
1 in 60
1 in 100
1 in 120
None of these
Q.3
The screens are fixed
Perpendicular to the direction of flow
Parallel to the direction of flow
At an angle 30° to 60° to the direction of flow
None of these
Q.4
In case of sewer lines
Water test is carried out to check water tightness of the joints
Test for straightness is carried out with the help of a lamp and mirror
Obstruction test is carried out with the help of smooth ball of diameter 13 mm
All the above
Q.5
In olden days the type of section adopted in trunk and out fall sewers was
Parabolic shaped
Horse shoe shaped
Egg shaped
Circular shaped
Q.6
The sewer which collects the discharge from a collecting system and delivers it to a treatment plant, is known
House sewer
Lateral sewer
Branch sewer
Sewer outfall
Q.7
The reduced levels of the string at the consecutive sight rails A and B are 203.575 m, 203.475 m respectively. If the difference of their R.D.s is 10 m, the gradient of the sewer line is
1 in 100 upward
1 in 500 upward
1 in 100 downward
1 in 503 upward
Q.8
The sewer pipes
Carry sewage as gravity conduits
Are designed for generating self-cleansing velocities at different discharge
Should resist the wear and tear caused due to abrasion
All the above
Q.9
The detention time (t) of a settling tank, may be defined as the time required for
A particle to travel along its length
A particle to travel from top surface to bottom sludge zone
The flow of sewage to fill the tank
None of these
Q.10
Pick up the incorrect size of stone ware sewers
52.5 cm
67.5 cm
82.5 cm
None of these
Q.11
The stone ware sewers
Are used for carrying sewage and drainage from houses
Are manufactured from clays and shale
After casting are dried and burnt at temperature 150°C, 700°C and 1200°C
All the above
Q.12
Pick up the correct statement from the following:
The materials separated by screens, is called screenings
The screenings are disposed off either by burning or by burial or by dumping
The process of burning the screenings, is known as compositing
All the above
Q.13
The pH value of fresh sewage is usually
Equal to 7
More than 7
Less than 7
Equal to zero
Q.14
If is the diameter of upper circular portion, the overall depth of New Egg shaped sewer section, is
1.250 D
1.350 D
1.425 D
1.625 D
Q.15
Design period of 40 to 50 years is adopted for
Branch sewers
Main sewers
Trunk sewers
All the above
Q.16
Setting out the alignments of sewers may start from
City
Out-fall
Tail end
Any point
Q.17
Pick up the correct statement from the following:
The maximum rate of storm runoff is called peak drainage discharge
Rational method of estimating peak run off, may be used precisely for areas less than 50 hectares
The period after which the entire area starts contributing to the runoff, is called the time of concentration
All the above
Q.18
If the diameter of sewer is 225 mm, the gradient required for generating self cleansing velocity, is
1 in 60
1 in 100
1 in 120
None of these
Q.19
The settlement velocity of a solid (diameter 0.5 mm, specific gravity 1.75) in water having temperature 10°C, is
213.5 cm/sec
313.5 cm/sec
413.5 cm/sec
500 cm/sec
Q.20
For evaporation and measurement of settable solids, the apparatus used, is
A jar
A breaker
A test tube
An Imhoff cone
Q.21
Sewer manholes are generally provided at
The change of gradient
The change of direction
The junctions of sewers
All of these
Q.22
Bio-chemical oxygen demand (BOD) for the first 20 days in generally referred to
Initial demand
First stage demand
Carbonaceous demand
All of these
Q.23
The rate of accumulation of sludge per person per year, is
10 litres
15 litres
20 litres
25 litres
Q.24
The sewage discharge in a detritus tank of a treatment plant is 576 litres/sec with flow velocity of 0.2 m/sec. If the ratio of width to depth is 2, the depth is
100 cm
110 cm
120 cm
150 cm
Q.25
To maintain aerobic biological activity, the moisture content of the compost mass should be about
45 %
50 %
55 %
60 %
Q.26
As compared to fresh river water, sea water contains oxygen
10% less
20% less
10% more
20% more
Q.27
You are asked to design sewer pipes of diameters 0.4 m to 0.9 m at maximum flow, you will assume the sewer flow running at
Full depth
Half full
Two third full
Three fourth full
Q.28
The asbestos cement pipes are generally laid
Horizontally
Vertically
At an angle of 30°
At an angle of 60°
Q.29
pH value of sludge during alkaline regression stage, is
More than 7
Less than 7
Less than 6
More than 6
Q.30
Depletion of ozone layer in the outer atmosphere may cause
Lung cancer
Skin cancer
Bronchitis
Heart disorder
Q.31
For treating the sewage of a large city, you will recommend
A sedimentation tank and an activated sludge treatment plant
A plant consisting of Imhoff tanks with low rate trickling filters
Sedimentation tanks with high rate trickling filters
None of these
Q.32
In sewers the effect of scouring is more on
Top side
Bottom side
Horizontal side
All sides
Q.33
The temperature affects the
Biological activity of bacteria in sewage
Solubility of gases in sewage
Viscosity of sewage
All the above
Q.34
The drainage area of a town is 12 hectares. Its 40% area is hard pavement ( K = 0.85), the 40% area is unpaved streets (K = 0.20) and the remaining is wooded areas (K = 0.15). Assuming the time of concentration for the areas as 30 minutes and using the formula Ps = 900/(t + 60) the maximum run off is
0.10 cumec
0.12 cumec
0.15 cumec
0.20 cumec
Q.35
The sewage treatment in septic tanks is due to
Anaerobic decomposition
Aerobic decomposition
Parasitic decomposition
None of these
Q.36
To prevent settling down of sewage both at the bottom and on the sides of a large sewer, self-cleaning velocity recommended for Indian conditions, is
0.50 m/sec
0.60 m/sec
0.70 m/sec
0.75 m/sec
Q.37
Which one of the following gases is most significant as air pollutant?
Carbondioxide
Oxygen
Nitrogen
Sulphur-dioxide
Q.38
The settling velocity of a spherical particle of diameter less than 0.1 mm as per Stock’s law, is
Vs = 418 (Gs – Gw) d [(3T + 70)/100]
Vs = 418 (Gs – Gw)d² [(3T + 70)/100]
Vs = 218 (Gs – Gw)d² [(3T + 70)/100]
Vs = 218 (Gs – Gw)d [(3T + 70)/100]
Q.39
The small sewers are cleaned by
Flushing
Cane rodding
Wooden pills
None of these
Q.40
For estimating the peak run off the rational formula Q = 0.0278 KpA was evolved by
Kinchling
Lloyd Davis
Frubling
All the above
Q.41
The density of population over 40 hectares is 250/hectare. If water supply demand per day is 200 litres and sewage discharge is 80% of water supply, the sewage flow in sewers of separate system, is
0.05552 cumec
0.05554 cumec
0.05556 cumec
0.0556 cumec
Q.42
Which one of the following statements regarding septic tanks is wrong?
A gap of 7.5 cm between the bottom of the covering slab and the top level of scum is provided
The outlet invert level is kept 5 to 7.5 cm below the inlet invert level
The minimum width of septic level is 90 cm
The depth of tank is kept equal to its width
Q.43
If D.O. concentration falls down to zero in any natural drainage, it indicates the zone of
Degradation
Active decomposition
Recovery
Cleaner water
Q.44
The standard B.O.D. of water is taken for
1 day
2 days
3 days
5 days
Q.45
Dried sewage after treatment is used as
Fertilizer
Building material
Chemical for lowering B.O.D.
Base material for paints
Q.46
The factor responsible for purification of sewage in river is
Hydrology
Dissolved oxygen in water
Temperature
All the above
Q.47
The sewer which transports the sewage to the point of treatment, is called
House sewer
Out-fall sewer
Branch sewer
Main sewer
Q.48
The sewage treatment units in which anaerobic decomposition of organic matter is used, are called
Imhoff tanks
Trickling filters
Sludge sedimentation tanks
None of these
Q.49
The porosity of sediments in sewer pipes, is usually taken as
0.010
0.011
0.012
0.013
Q.50
If is the rugosity coefficient, is the bed slope of sewer, the velocity of flow in m/sec may be obtained by the formula V = (1/n) r
2
/
3
s
1
/
2
evolved by
Chezy
Manning
Bazin
Kutter
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