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Quiz 6
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Q.1
For large sewers, maximum distance between manholes may be
50 m
100 m
200 m
300 m
Q.2
In sewage, the solids in mg per litre is
100 to 500
500 to 1000
1000 to 1500
1500 to 2000
Q.3
For the COD test of sewage, organic matter is oxidised by K₂Cr₂O₇ in the presence of
H₂SO₄
HNO₃
HCl
None of these
Q.4
Pick up the correct statement from the following:
The water supply pipes carry pure water free from solid particles
The water supply pipes get clogged if flow velocity is less than self cleansing velocity
The sewers may be carried up and down the hills and valleys
The sewer pipes are generally laid along level hills
Q.5
An inverted siphon is designed generally for
One pipe
Two pipes
Three pipes
Four pipes
Q.6
In sewers the gas generally found, is
Hydrogen sulphide (H
2
S)
Carbon dioxide (CO
2
)
Methane (CH
4
)
All the above
Q.7
Kjeldahl nitrogen is a mixture of
Ammonia and nitrogen
Nitrogen and organic nitrogen
Organic nitrogen and ammonia
All the above
Q.8
The intensity of rain is expressed in
cm/minute
cm/hour
cm/day
None of these
Q.9
The ratio of maximum sewage flow to average sewage flow for mains up to 1 m in diameter, is
1.5
2.0
3.0
4.0
Q.10
The sewerage system originates from
House sewers
Lateral sewers
Branch sewers
Main sewers
Q.11
In a city the ratio of the drainage to sewage is 20, the percentage discharge passing through non-monsoon periods, is
5
10
15
20
Q.12
Pick up the correct statement from the following:
Hydrogen sulphide gas in excess, may cause corrosion of concrete sewers
4 ppm of Dissolved Oxygen (D.O.) is ensured before discharging the treated sewage in river
Solubility of oxygen in sewage is 95% of that of distilled water
All the above
Q.13
Pick up the correct statement from the following:
In treated sewage, 4 ppm of D.O. is essential
Only very fresh sewage contains some dissolved oxygen
The solubility of oxygen in sewage is 95% that is in distilled water
All the above
Q.14
For house drainage minimum gradient is
1 in 60
1 in 80
1 in 10
1 in 400
Q.15
To test chemical oxygen demand (C.O.D.) of sewage, organic matter is oxidised by potassium dichromate in the presence of
Hydrochloric acid
Sulphuric acid
Nitric acid
Citric acid
Q.16
Pathogens (or pathogenic bacterias) in water may cause
Typhoid
Cholera
Dysentery
All the above
Q.17
The grit chambers of sewage treatment plants, are generally cleaned after
2 days
7 days
12 days
14 days
Q.18
Cement concrete sewers are only suitable if non-scouring velocity is between
2.5 to 3.0 m/sec
3.0 to 4.0 m/sec
3.5 to 4.5 m/sec
4.5 to 5.5 m/sec
Q.19
Pick up the correct statement from the following:
Maximum daily flow = 2 times the average daily flow
Maximum daily flow = ⅔ × average daily flow
Sewers are designed for minimum permissible velocity at minimum flow
All the above
Q.20
Which one of the following resists hydrogen sulphide corrosion?
R.C.C.
Glazed stone wares
Asbestos cement
Glazed ware
Q.21
The gas evolved in sewers is
Carbondioxide
Hydrogen sulphide
Methane
All of these
Q.22
For sewers, inverted siphon is provided for
One pipe
Two pipes
Three pipes
Four pipes
Q.23
The digested sludge from septic tanks, is removed after a maximum period of
3 years
3.5 years
4 years
5 years
Q.24
The underground sewers are more subjected to
Tensile force
Compressive force
Bending force
Shearing force
Q.25
The formula which accepts the value of rugosity coefficient n = 0.012 to be used in Manning’s formula, is given by
Bazin
Crimp and Bruges
William-Hazen
Kutter
Q.26
In SI units the power of sound is represented in
Kgs
Joules
Newtons
Watts
Q.27
Disposal to sewage in large cities, is done in
Irrigation
Dilution
Oxidation
Purification
Q.28
In a sludge tank, the gas mainly produced, is
Oxygen
Nitrogen
Hydrogen
Carbon dioxide
Q.29
A five day B.O.D. at 15°C of the sewage of a town is 100 kg/day. If the 5 day B.O.D. per head at 15°C for standard sewage is 0.1 kg/day, the population equivalent is
100
1000
5000
10000
Q.30
The gas which may cause explosion in sewers, is
Carbondioxide
Methane
Ammonia
Carbon monoxide
Q.31
Pick up the correct statement from the following:
Small sewers are cleaned by flushing
Medium sewers are cleaned by cane rodding
Medium sewers may be cleaned by pills
All the above
Q.32
In sewers the velocity of flow should not be
More than the self-cleansing velocity
Less than the self-cleansing velocity
Less than 10 m/sec
More than 20 m/sec
Q.33
The ratio of the diameter of a circular section and the side of a square section hydraulically equivalent, is
1.095
1.085
1.075
1.065
Q.34
Pick up the correct statement from the following:
The sewer pipes of sizes less than 0.4 m diameter are designed as running full at maximum discharge
The sewer pipes of sizes greater than 0.4 m diameter are designed as running 2/3rd or 3/4th full at maximum discharge
The minimum design velocity of sewer pipes is taken as 0.8 m/sec
All the above
Q.35
‘Cowl’ is provided at
Lower end of ventilating column
Upper end of ventilating column
Upper end of the manhole
First step in manhole
Q.36
The formula V = (1/n) r
2
/
3
Chezy’s formula
Bazin’s formula
Kutter’s formula
Manning’s formula
Q.37
A drop manhole is provided if
A sewer drops from a height
A branch sewer joins the main sewer at higher level
A lamp is inserted to check obstruction
None of these
Q.38
A well oxidized sewage contains nitrogen mainly as
Nitrates
Nitrites
Free ammonia
None of these
Q.39
The settlement of a particle in sedimentation tank, is affected by
Velocity of flow
Viscosity of water
Size and shape of solid
All the above
Q.40
Skimming tanks are
Used to remove the grease and oil
Those from which sludge is skimmed out
Tanks provided with self- cleansing screens
Improved version of grit chambers
Q.41
Sludge banks are formed if sewage is disposed of in
Rivers
Seas
Lakes
None of these
Q.42
The rate of accumulation of sludge in septic tanks is recommended as
30 litres/person/year
25 litres/person/year
30 litres/person/month
25 litres/person/month
Q.43
Pick up the correct statement from the following:
Anaerobic bacteria flourish in the absence of oxygen
Aerobic bacteria flourish in the presence of oxygen
Facultative bacteria flourish with or without oxygen
All the above
Q.44
The most widely used pump for lifting sewage is
Centrifugal pump
Reciprocating pump
Pneumatic ejector
Air pressure pump
Q.45
The non-clog pump which permits solid matter to pass out with the liquid sewage, is
Centrifugal pump
Reciprocating pump
Pneumatic ejector
None of these
Q.46
The arrangement made for passing the sewer line below an obstruction below the hydraulic gradient lines called
Inverted syphon
Depressed sewer
Sag pipe
all of these
Q.47
No treatment of the sewage is given if dilution factor is
Less than 150
Between 150 to 200
Between 200 to 300
More than 500
Q.48
For providing an Indian type W.C., the R.C.C. slabs in the toilet portion
Should be sunk by 20 cm
Should be kept 20 cm above the adjacent portion
Should be sunk by 50 cm
Need not be sunk
Q.49
In Chezy’s formula V = C rs for calculating the velocity of flow in circular sewer of diameter running full, the value of hydraulic mean radius is
D/1
D/2
D/3
D/4
Q.50
In septic tanks,
Free board of 0.3 m may be provided
The baffles or tees are extended up to top level of scum
The clear space between the baffle top and covering slab is about 7.5 cm
All the above
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