Waste Water Engineering MCQs : This section focuses on the "Waste Water Engineering". These Multiple Choice Questions (MCQs) should be practiced to improve the Waste Water Engineering skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.
Question 1
A rain sanitary sewer is constructed to carry
A. sanitary sewage
B. storm sewage
C. surface water
D. ground water
Question 2
A rainfall may be classified as acidic if its pH value is less or equal to
A. 6
B. 7
C. 5
D. 6.5
Question 3
A sewer pipe contains 1 mm sand particles of specific gravity 2.65 and 5 mm organic particles of specific gravity 1.2, the minimum velocity required for removing the sewerage, is
A. 0.30 m/sec
B. 0.35 m/sec
C. 0.40 m/sec
D. 0.45 m/sec
Question 4
Aerobic bacterias
A. flourish in the presence of free oxygen
B. consume organic matter as their food
C. oxidise organic matter in sewage
D. All the above.
Question 5
An inverted siphon is designed generally for
A. one pipe
B. two pipes
C. three pipes
D. four pipes.
Question 6
Assertion (A) : Discharging the effluents from the oxidation ponds just up stream of lakes or reservoirs is undesirable. Reason (R) : The discharged algae get settled in the reservoirs and cause anaerobic decomposition and other water qualities.
A. Both A and R are true and R is the correct explanation of A
B. Both A and R are true but R is not a correct explanation of A
C. A is true but R is false
D. A is false but R is true.
Question 7
Bio-chemical oxygen demand (BOD) for the first 20 days in generally referred to
A. initial demand
B. first stage demand
C. carbonaceous demand
D. all of these.
Question 8
Chlorination of water is done for the removal of
A. bacterias
B. suspended solids
C. sediments
D. hardness.
Question 9
Dilution method of disposing off sewage, is not preferred to
A. when sewage is fresh
B. when diluting water has high dissolved oxygen content
C. when diluting water is used for water supply near the point of sewage disposed
D. when the diluting water is having flow currents
Question 10
Disposal to sewage in large cities, is done in
A. irrigation
B. dilution
C. oxidation
D. putrifaction.
Question 11
Flocculated particles do not change their
A. size
B. shape
C. weight
D. none of these.
Question 12
For evaporation and measurement of settlable solids, the apparatus used, is
A. a jar
B. a breaker
C. a test tube
D. an Imhoff cone.
Question 13
For house drainage minimum gradient is
A. 1 in 60
B. 1 in 80
C. 1 in 10
D. 1 in 400
Question 14
For non-scouring velocity 5 m/sec, the type of sewers generally preferred to, is
A. cast iron sewers
B. cement concrete sewers
C. glazed bricks sewers
D. stone ware sewers.
Question 15
For the COD test of sewage, organic matter is oxidised by K2Cr207 in the presence of
A. H2SO4
B. HNO3
C. HCl
D. none of these.
Question 16
For the survival of fish in a river stream, the minimum dissolved oxygen is prescribed
A. 3 PPm
B. 4 PPm
C. 5 PPm
D. 10 ppm.
Question 17
For treating the sewage of a large city, you will recommend
A. a sedimentation tank and an activated sludge treatment plant
B. a plant consisting of Imhoff tanks with low rate trickling filters
C. sedimentation tanks with high rate trickling filters
D. none of these.
Question 18
House connections to the laterals is generally made by
A. R.C.C.
B. P.C.C.
C. Cast iron
D. Glazed stonewares.
Question 19
If 2% solution of a sewage sample is incubated for 5 days at 20°C and depletion of oxygen was found to be 5 ppm, B.O.D. of the sewage is
A. 200 ppm
B. 225 ppm
C. 250 ppm
D. None of these.
Question 20
If D is the diameter of upper circular portion, the overall depth of a standard egg shaped section, is
A. D
B. 1.25 D
C. 1.5 D
D. 1.75 D
Question 21
If the diameter of sewer is 225 mm, the gradient required for generating self cleansing velocity, is
A. 1 in 60
B. 1 in 100
C. 1 in 120
D. none of these.
Question 22
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
A. 2 hours
B. 3 hours
C. 4 hours
D. 5 hours.
Question 23
If the side of a square sewer is 1000 mm, the diameter of a hydraulically equivalent circular section, is
A. 1045 mm
B. 1065 mm
C. 1075 mm
D. 1095 mm.
Question 24
In a fully mechanised composting plant, involves
A. mechanized receipt
B. mechanized segregation
C. mechanized pulverising of refuse
D. all of these.
Question 25
In olden days the type of section adopted in trunk and out fall sewers was
A. parabolic shaped
B. horse shoe shaped
C. egg shaped
D. circular shaped.
Question 26
In primary sedimentation, the 0.2 mm inorganic solids get separated if specific gravity is
A. 2.25
B. 2.5
C. 2.55
D. 2.65
Question 27
In R.C. sewer pipes, the percentage longitudinal reinforcement to the cross-sectional area of concrete is kept
A. 10
B. 5
C. 2
D. 0.25
Question 28
In sewers the effect of scouring is more on
A. top side
B. bottom side
C. horizontal side
D. all sides.
Question 29
In SI units the power of sound is represented in
A. kgs
B. joules
C. neutons
D. watts.
Question 30
Pick up the correct statement from the following :
A. In treated sewage, 4 PPm of D.O. is essential
B. Only very fresh sewage contains some dissolved oxygen
C. The solubility of oxygen in sewage is 95% that is in distilled water
D. All the above.
Question 31
Pick up the in-correct statement from the following :
A. Manholes are provided in sewer pipes at suitable intervals
B. Catch basins are generally provided in sewers for carrying drainage discharge
C. Inlets are generally provided in all sewers
D. None of these.
Question 32
Removal of oil and grease from sewage, is known
A. screening
B. skimming
C. filtration
D. none of these.
Question 33
Self-cleansing velocity is
A. velocity at dry weather flow
B. velocity of water at flushing
C. velocity at which no accumulation remains in the drains
D. velocity of water in a pressure filter.
Question 34
The asbestos cement pipes are generally laid
A. horizontally
B. vertically
C. at an angle of 30°
D. at an angle of 60°.
Question 35
The coagulant widely used for sewage treatment, is
A. alum
B. ferric chloride
C. ferric sulphate
D. chlorinated copperas.
Question 36
The dimensions of a rectangular settling tank are : length 24 m, width 6 m and depth 3 m. If 2 hour detention period for tanks is recommended, the rate of flow of sewage per hour, is
A. 204 cu m
B. 208 cu m
C. 212 cu m
D. 216 cu m
Question 37
The gas which may cause explosion in sewers, is
A. carbondioxide
B. methane
C. ammonia
D. carbon monoxide.
Question 38
The minimum recommended diameter of sewers, is
A. 5 cm
B. 10 cm
C. 15 cm
D. 20 cm.
Question 39
The non-clog pump which permits solid matter to pass out with the liquid sewage, is
A. centrifugal pump
B. reciprocating pump
C. pneumatic ejector
D. none of these.
Question 40
The rate of accumulation of sludge in septic tanks is recommended as
A. 30 litres/person/year
B. 25 litres/person/year
C. 30 litres/person/month
D. 25 litres/person/month.
Question 41
The ratio of maximum sewage flow to average sewage flow for mains up to 1 m in diameter, is
A. 1.5
B. 2
C. 3
D. 4
Question 42
The ratio of minimum hourly flow to the average flow of sewage is
A. 01-Apr
B. 01-Mar
C. 01-Feb
D. 03-Apr
Question 43
The screens are fixed
A. perpendicular to the direction of flow
B. parallel to the direction of flow
C. at an angle 30° to 60° to the direction of flow
D. none of these.
Question 44
The width of a rectangular sewer is twice its depth while discharging 1.5 m/sec. The width of the sewer is
A. 0.68 m
B. 0.88 m
C. 1.36 m
D. 1.76 m.
Question 45
When drainage to sewage ratio is 20, the peak dry weather flow is
A. 20% of the design discharge
B. slightly less than 5% of the design discharge
C. slightly more than 5% of the design discharge
D. none of these.
Question 46
The effluent of a septic tank is
A. Fit for discharge into any open drain
B. Foul and contains dissolved and suspended solids
C. As good as that from a complete treatment
D. None of these
Question 47
5 days-biochemical oxygen demand (BOD5) is taken at a temperature of
A. 0°C
B. 15°C
C. 20°C
D. 25°C
Question 48
The bottom of the sewage inlet chamber of septic tanks, is provided an outward slope
A. 1 in 5
B. 1 in 10
C. 1 in 15
D. 1 in 20
Question 49
Drop manholes are the manholes
A. Without entry ladders
B. Without manhole covers
C. With depths more than 3.5 m
D. Having drains at different levels
Question 50
For laying a sewer line in a trench of 2 m width, an offset line is marked on the ground parallel to the given centre line at a distance of
A. 100 cm
B. 120 cm
C. 140 cm
D. 160 cm
Question 51
The rainfall at any place may be determined by
A. Its intensity
B. Its direction
C. Its frequency
D. All the above
Question 52
The clarigesters are
A. Circular septic tanks
B. Rectangular septic tanks
C. Circular Imhoff double tanks with bottom hoppers
D. Circular Imhoff double storey tanks without bottom hoppers
Question 53
If the grit in grit chambers is 4.5 million litres per day, its cleaning is done
A. Manually
B. Mechanically
C. Hydraulically
D. Electrically
Question 54
A manhole is classified as shallow if its depth is between
A. 0.4 to 0.5 m
B. 0.5 to 0.7 m
C. 0.7 to 0.9 m
D. 0.9 to 1.20 m
Question 55
R.M.O. expenses include
A. Running expenses
B. Maintenance expenses
C. Operation expenses
D. All the above
Question 56
15 cumecs, the depth d and width are related by For drains up to
A. d = 0.2 B
B. d = 0.5 B
C. B = 0.2 d
D. B = 0.5 d
Question 57
Dry weather flow is:
A. Average daily rate of flow
B. Average monthly rate of flow
C. Average annual rate of flow
D. Water supply allowance per capita
Question 58
The pH value of sewage is determined with the help of
A. Imhoff Cone
B. Turbid meter
C. Potentiometer
D. None of these
Question 59
The settling velocity of the particles larger than 0.06 mm in a settling tank of depth 2.4 is 0.33 m per sec. The detention period recommended for the tank, is
A. 30 minutes
B. 1 hour
C. 1 hour and 30 minutes
D. 2 hours
Question 60
Drop manholes at the junctions of sewer lines, are provided if
A. Invert level of a branch sewer is more than 60 cm that of the main sewer
B. Sewer line runs along a main road
C. Ordinary manhole cannot be built
D. Two sewer lines intersect
Question 61
The discharge per unit plan area of a sedimentation tank, is generally called
A. Over flow rate
B. Surface loading
C. Over flow velocity
D. All the above
Question 62
It is customary to design a sewer for D.W.F. on the basis of
A. Average demand
B. Twice the average demand
C. Thrice the average demand
D. Four times the average demand
Question 63
In trickling filter, B.O.D. is reduced to
A. 30 to 40%
B. 40 to 60%
C. 60 to 80%
D. 80 to 90%
Question 64
The recommended detention period for grit chambers is
A. 1 minute
B. 2 minutes
C. 3 minutes
D. 5 minutes
Question 65
The value of Chezy’s constant C = 157.6/(1.81 + K/ ) is used in
A. Chezy’s formula
B. Bazin’s formula
C. Kutter’s formula
D. Manning’s formula
Question 66
The maximum spacing of manholes specified by Indian standard in sewers upto 0.3 m diameter is
A. 20 m
B. 30 m
C. 45 m
D. 75 m
Question 67
Clogging of sewers, is caused due to
A. Silting
B. Low discharge
C. Greasy and oily matters
D. All the above
Question 68
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) r2/3 s1/2 evolved by
A. Chezy
B. Manning
C. Bazin
D. Kutter
Question 69
In a sedimentation tank (length L, width B, depth D) the settling velocity of a particle for a discharge Q, is
A. Q/(B × D)
B. Q/(L × D)
C. Q/L
D. Q/(B × L)
Question 70
Maximum permissible velocity 1.5 m/sec, is adopted in drains
A. With beds of rocks and gravels
B. Lined with stones
C. Both A. and B.
D. Neither A. nor B.
Question 71
Aerobic bacterias
A. Flourish in the presence of free oxygen
B. Consume organic matter as their food
C. Oxidise organic matter in sewage
D. All the above
Question 72
In very first stage of decomposition of the organic matter in sewage
A. Nitrites are formed
B. Nitrates are formed
C. Carbondioxide is formed
D. Ammonia is formed
Question 73
The quantity of liquid waste which flows in sewers during the period of rainfall, is known
A. Sanitary sewage
B. Industrial waste
C. Storm sewage
D. None of these
Question 74
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
A. 0.50 m/sec
B. 0.60 m/sec
C. 0.70 m/sec
D. 0.75 m/sec
Question 75
The layers of vegetable wastes and night soil alternatively piled above the ground to form a mound, is called
A. A heap
B. Plateau
C. Windrow
D. None of these
Question 76
Which one of the following gases is most significant as air pollutant?
A. Carbondioxide
B. Oxygen
C. Nitrogen
D. Sulphur-dioxide
Question 77
The standard B.O.D. of water is taken for
A. 1 day
B. 2 days
C. 3 days
D. 5 days
Question 78
Flocculated particles do not change their
A. Size
B. Shape
C. Weight
D. None of these
Question 79
Dried sewage after treatment is used as
A. Fertilizer
B. Building material
C. Chemical for lowering B.O.D.
D. Base material for paints
Question 80
The sewer which transports the sewage to the point of treatment, is called
A. House sewer
B. Out-fall sewer
C. Branch sewer
D. Main sewer
Question 81
Dilution method of disposing of sewage, is not preferred to
A. When sewage is fresh
B. When diluting water has high dissolved oxygen content
C. When diluting water is used for water supply near the point of sewage disposed
D. When the diluting water is having flow currents
Question 82
The temperature affects the
A. Biological activity of bacteria in sewage
B. Solubility of gases in sewage
C. Viscosity of sewage
D. All the above
Question 83
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
A. 0.10 cumec
B. 0.12 cumec
C. 0.15 cumec
D. 0.20 cumec
Question 84
In case of Imhoff tanks,
A. The shape is rectangular
B. Detention period is 2 hours
C. The velocity of flow is restricted to 0.30 m/minute
D. All the above
Question 85
The sewage treatment in septic tanks is due to
A. Anaerobic decomposition
B. Aerobic decomposition
C. Parasitic decomposition
D. None of these
Question 86
Which one of the following statements regarding septic tanks is wrong?
A. A gap of 7.5 cm between the bottom of the covering slab and the top level of scum is provided
B. The outlet invert level is kept 5 to 7.5 cm below the inlet invert level
C. The minimum width of septic level is 90 cm
D. The depth of tank is kept equal to its width
Question 87
If a 2% solution of sewage sample is incubated for 5 days at 20°C and the dissolved oxygen depletion was found to be 8 mg/l. The BOD of the sewage is
A. 100 mg/l
B. 200 mg/l
C. 300 mg/l
D. 400 mg/l
Question 88
If D.O. concentration falls down to zero in any natural drainage, it indicates the zone of
A. Degradation
B. Active decomposition
C. Recovery
D. Cleaner water
Question 89
If 2% solution of a sewage sample is incubated for 5 days at 20°C and depletion of oxygen was found to be 5 ppm, B.O.D. of the sewage is
A. 200 ppm
B. 225 ppm
C. 250 ppm
D. None of these
Question 90
The asbestos cement sewers are
A. Light in weight
B. Not structurally strong to bear large compressive stress
C. Susceptible to corrosion by sulphuric acid
D. All the above
Question 91
If the depletion of oxygen is found to be 2.5 mg/litre after incubating 2.5 ml of sewage diluted to 250 ml for 5 days at 20°C, B.O.D. of the sewage is
A. 50 mg/l
B. 100 mg/l
C. 150 mg/l
D. 250 mg/l
Question 92
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
A. D’ = 0.64 D
B. D’ = 0.74 D
C. D’ = 0.84 D
D. D’ = 0.94 D
Question 93
hydraulically equivalent, the relationship which holds good, is
A. D8/3 = 4 b8/3
B. D3/8 = 4 b3/8
C. D2/3 = 4 b2/3
D. D3/2 = 4 b3/2
Question 94
If the depletion of oxygen is found to be 5 ppm after incubating a 2.5% solution of sewage sample for 5 days at 21°C, B.O.D. of the sewage is
A. 50 ppm
B. 100 ppm
C. 150 ppm
D. 200 ppm
Question 95
For design of sewers, percentage of sewage discharge is assumed
A. 65 to 70%
B. 70 to 75%
C. 75 to 80%
D. 85%
Question 96
Nitrogen cycle of sewage, is
A. Liberation of ammonia-formation of nitrites-formation of nitrates-liberation of nitrogen
B. Liberation of nitrogen-liberation of ammonia-formation of nitrites- formation of nitrates
C. Liberation of nitrogen-formation of nitrates-formation of nitrites-liberation of ammonia
D. Formation of nitrates-formation of nitrites-liberation of nitrates-liberation of nitrates
Question 97
Discrete or granular particles change their
A. Size
B. Shape
C. Weight
D. None of these
Question 98
If the discharge of a sewer running half is 628 1.p.s., i = 0.001, and n = 0.010, the diameter of the sewer, is
A. 1.39 m
B. 1.49 m
C. 1.59 m
D. 1.69 m
Question 99
The suitable cross-section of sewers to carry combined flow, is
A. Circular
B. Egg shaped
C. Rectangular
D. Horse shoe shaped
Question 100
Facultative bacteria survive in
A. The presence of oxygen
B. The absence of oxygen
C. Both cases A and B
D. Neither A nor B
Question 101
Acid regression stage of sludge digestion at a temperature 21°C extends over a period of
A. 15 days
B. 30 days
C. 60 days
D. 90 days
Question 102
A nuisance is experienced in diluting water if dilution factor is less than
A. 100
B. 60
C. 40
D. 20
Question 103
The width of a settling tank with 2 hour detention period for treating sewage 378 cu m per hour, is
A. 5 m
B. 5.5 m
C. 6.5 m
D. 7 m
Question 104
For non-scouring velocity 5 m/sec, the type of sewers generally preferred to, is
A. Cast iron sewers
B. Cement concrete sewers
C. Glazed bricks sewers
D. Stone ware sewers
Question 105
If the side of a square sewer is 1000 mm, the diameter of a hydraulically equivalent circular section, is
A. 1045 mm
B. 1065 mm
C. 1075 mm
D. 1095 mm
Question 106
The drop man holes are generally provided in sewers for
A. Industrial areas
B. Large town ships
C. Hilly town ships
D. Cities in plains
Question 107
A manhole is generally provided at each
A. Bend
B. Junction
C. Change of gradient
D. All the above
Question 108
The flow velocity in detritus tanks is
A. 0.05 m/sec
B. 0.09 m/sec
C. 1.25 m/sec
D. None of these
Question 109
In normal conditions, the period for sludge digestion, is
A. 10 days
B. 20 days
C. 30 days
D. 60 days
Question 110
The amount of oxygen consumed by the aerobic bacterias which cause the aerobic biological decomposition of sewage, is known
A. Bio-Chemical Oxygen Demand (B.O.D.)
B. Dissolved Oxygen (D.O.)
C. Chemical Oxygen Demand (C.O.D.)
D. None of these
Question 111
The first stage of neutral process of sludge digestion, is
A. Acid fermentation
B. Acid regression
C. Alkaline fermentation
D. None of these
Question 112
The sewer pipe which carries sewage from a building for immediate disposal is
A. House sewer
B. Lateral sewer
C. Intercepting sewer
D. Main sewer
Question 113
Removal of oil and grease from sewage, is known
A. Screening
B. Skimming
C. Filtration
D. None of these
Question 114
For a continuous flow type of sedimentation tanks
A. Width of the tank is normally kept about 6 m
B. Length of the tank is normally kept 4 to 5 times the width
C. Maximum horizontal flow velocity is limited to 0.3 m/minute
D. All the above
Question 115
The use of coarse screens for the disposal of sewage, may be dispensed with by
A. Comminutor
B. Shredder
C. Both A and B
D. Neither A nor B
Question 116
Are available in size Stoneware sewers
A. 10 cm
B. 15 cm
C. 20 cm
D. All the above
Question 117
In a residential colony, sewers of diameters 100 mm, 150 mm and 225 mm were laid with a gradient 1 in 120. Which portion of the sewage system does not choke in due course of time?
A. 100 mm dia
B. 150 mm dia
C. 225 mm dia
D. All of these
Question 118
For trunk sewers more than 1.25 m in diameter, the ratio of the maximum daily sewage flow to the average daily sewage flow is assumed
A. 1.5
B. 2
C. 2.5
D. 3
Question 119
Oxidation process results in the formation of
A. Carbon dioxide
B. Nitrates
C. Sulphates
D. All the above
Question 120
For sewer mains of 0.5 to 1 m diameter, the ratio of maximum daily sewage flow to the average daily sewage flow is assumed
A. 1.5
B. 2
C. 2.5
D. 3
Question 121
The spacing of man holes along a straight portion of a sewer is 300 m, the diameter of the sewer may be
A. 0.9 cm
B. 1.2 m
C. 1.5 m
D. > 1.5 m
Question 122
Pick up the correct statement from the following:
A. Indore method of composting involves decomposition under aerobic conditions
B. Bangalore method of composting involves decomposing under anaerobic conditions
C. Fully stabilised refuse by the Bangalore method of compositing is a powdery mass called humus
D. all of these
Question 123
Pick up the correct statement from the following:
A. Inlets are provided on the road surface at the lowest point for draining rain water
B. Inlets are generally provided at an interval of 30 m to 60 m along straight roads
C. Inlets having horizontal openings, are called horizontal inlets
D. All the above
Question 124
The disintegrating pump in which solid matter is broken up before passing out, is
A. Centrifugal pump
B. Reciprocating pump
C. Pneumatic ejector
D. None of these
Question 125
Hume steel pipes are
A. Steel pipes
B. Steel shell coated from inside with cement mortar
C. Steel shell coated from outside with cement mortar
D. Both B and C
Question 126
In a sludge digestion tank if the moisture content of sludge V1 litres is reduced from p1 % to p2 % the volume V2 is
A. [(100 + P1)/(100 – P2)] V1
B. [(100 – P1)/(100 + P2)] V1
C. [(100 – P1)/(100 – P2)] V1
D. [(100 + P2)/(100 – P1)] V1
Question 127
The ratio of maximum sewage flow to average sewage flow for trunk mains having diameters more than 1.25 m, is
A. 1.5
B. 2
C. 3
D. 4
Question 128
Lead caulked joints are used for laying
A. Stone ware pipes
B. Earthenware pipes
C. C.I. pipes
D. G.I. pipes
Question 129
The minimum diameter of sewer to be adopted is
A. 10 cm
B. 12.5 cm
C. 15 cm
D. 25 cm
Question 130
Large diameter sewers subjected to external pressure alone, are reinforced
A. Near the inner surface of the pipe
B. Near the outer surface of the pipe
C. Both A and B
D. With elliptical cage
Question 131
In a grit chamber of a sewage treatment plant,
A. Flow velocity 0.15 m to 0.3 m/sec is kept
B. Depth of 0.9 m to 1.20 m is kept
C. One minute of detention period is kept
D. All the above
Question 132
The presence of free ammonia in sewage, is detected by
A. Boiling
B. Adding potassium permanganate
C. Adding sulphuric acid
D. Phenol-di-sulphuric acid
Question 133
The rational formula for peak drainage discharge, was evolved by
A. Fruhling
B. Lloyd David
C. Kuichling
D. All of these
Question 134
In a trickling filter
A. Filtration process is used
B. Biological action is used
C. Neither A nor B
D. Both A and B
Question 135
In sewers designed with self cleansing velocity,
A. The bottom is silted
B. The bottom is scoured
C. Both silting and scouring occur at the bottom
D. Neither silting nor scouring occurs at the bottom
Question 136
The sewage treatment units in which anaerobic decomposition of organic matter is used, are called
A. Imhoff tanks
B. Trickling filters
C. Sludge sedimentation tanks
D. None of these
Question 137
The sewer that unloads the sewage at the point of treatment is called
A. Main sewer
B. Outfall sewer
C. Branch sewer
D. House sewer
Question 138
The porosity of sediments in sewer pipes, is usually taken as
A. 0.01
B. 0.011
C. 0.012
D. 0.013
Question 139
Sewer pipes are designed for maximum discharge with 25% to 33% vacant cross-sectional area for
A. Unexpected large scale infiltration of stream water
B. Unexpected increase in the population
C. Under estimates of maximum and average flows
D. All of the above
Question 140
The sludge does not contain waste water from
A. Bath rooms
B. Wash basins
C. Kitchen sinks
D. Toilets
Question 141
A cylindrical ejector having its height 2 m fills after every 10 minutes with a peak sewage discharge of 0.0157 cumec. The diameter of the ejector chamber, is
A. 2.30 m
B. 2.40 m
C. 2.45 m
D. 2.50 m
Question 142
Sewer pipes need be checked for
A. Minimum flow
B. Maximum flow
C. Both A and B
D. None of these
Question 143
In the activated sludge process
A. Aeration is continued till stability
B. Aeration is done with an admixture of previously aerated sludge
C. Sludge is activated by constant stirring
D. Water is removed by centrifugal action
Question 144
With self cleansing velocity in sewers
A. Silting occurs at bottom
B. Scouring occurs at bottom
C. Both silting and scouring occur at bottom
D. Neither silting nor scouring occurs at bottom
Question 145
In areas where rainy season is limited to a few months, the type of sewerage system recommended is
A. Combined system
B. Partially separate system
C. Separate system
D. None of these
Question 146
For trunk and out-fall, the type of sewers generally used, is
A. Standard egg shaped
B. Circular shaped
C. Horse shoe shaped
D. Parabolic shaped
Question 147
The spacing of bars of perforations of fine screens used for the treatment of sewage, is
A. 2 to 3 mm
B. 3 to 5 mm
C. 5 to 8 mm
D. 8 to 10 mm
Question 148
The spacing of bars for perforations in coarse screens used for the treatment of sewage, is
A. 20 mm
B. 30 mm
C. 40 mm
D. 50 mm
Question 149
Before discharging the foul sewage into rivers, it is generally treated by
A. Screening
B. Sedimentation
C. Oxidation
D. All the above
Question 150
The following is the physical characteristic of sewage
A. Turbidity
B. Colour
C. Odour
D. All the above
Question 151
Pick up the correct statement from the following:
A. pH value indicates acidity and alkalinity of sewage
B. In acidic sewage, the pH value is less than 7
C. In alkaline sewage, the pH value is more than 7
D. All the above
Question 152
If the flame of a miner's safety lamp in the upper layers of the sewer forms an explosive, the sewer certainly contains
A. Hydrogen sulphide
B. Carbon dioxide
C. Methane
D. Oxygen
Question 153
If a paper moistened with lead acetate for five minutes when placed in manhole turns black. The sewer certainly contains
A. Hydrogen sulphide
B. Carbon dioxide
C. Methane
D. Oxygen
Question 154
The most efficient cross section of sewers in a separate sewerage system is
A. Parabolic
B. Circular
C. Rectangular
D. New egged
Question 155
If the flame of a miner’s safety lamp in a manhole extinguishes within 5 minutes, the sewer certainly contains
A. Hydrogen sulphide
B. Carbon dioxide
C. Methane
D. Oxygen
Question 156
The pressure exerted by
A. The sewage when running full from inside, is called internal pressure
B. The internal pressure if any, causes tensile stress in the pipe material
C. Pressure sewers are designed to be safe in tension
D. All the above
Question 157
The most efficient cross-section of sewers in a combined sewerage system is
A. Parabolic
B. Circular
C. Rectangular
D. New egged
Question 158
The factor responsible for purification of sewage in river is
A. Hydrology
B. Dissolved oxygen in water
C. Temperature
D. All the above
Question 159
The minimum diameter of a sewer is kept
A. 10 cm
B. 15 cm
C. 20 cm
D. 25 cm
Question 160
Inter-distance between ventilation columns in a sewer line is kept
A. 25 to 50 m
B. 50 m to 100 m
C. 100 m to 150 m
D. 150 m to 300 m
Question 161
Pick up the incorrect statement from the following:
A. Manholes are provided in sewer pipes at suitable intervals
B. Catch basins are generally provided in sewers for carrying drainage discharge
C. Inlets are generally provided in all sewers
D. None of these
Question 162
3.0 ml of raw sewage is diluted to 300 ml. The D.O. concentration of the diluted sample at the beginning of the test was 8 mg/l. After 5 day-incubation at 20°C, the D.O. concentration was 5 mg/l. The BOD of raw sewerage is
A. 100 mg/l
B. 200 mg/l
C. 300 mg/l
D. 400 mg/l
Question 163
1000 kg of sewage contains
A. 0.112 kg in suspension
B. 0.112 kg in solution
C. 0.225 kg in solution
D. Both A and C of above
Question 164
Water content of sewage is about
A. 90 %
B. 95 %
C. 99 %
D. 99.9 %
Question 165
A circular sewer section is preferred to because
A. It is cheaper in construction
B. It provides maximum area for a given perimeter
C. It provides maximum hydraulic mean depth
D. All the above
Question 166
The ratio of minimum hourly flow to the average flow of sewage is
A. 1-4
B. 1-3
C. 1-2
D. 3-4
Question 167
In a fully mechanised composting plant, involves
A. Mechanized receipt
B. Mechanized segregation
C. Mechanized pulverising of refuse
D. All of these
Question 168
For drainage pipes in buildings the test applied before putting them to use, is
A. Water test
B. Smoke test
C. Straightness test
D. All the above
Question 169
During purification process of sewage the gas given off, is
A. Carbon dioxide
B. Hydrogen
C. Ammonia
D. All the above
Question 170
Antisyphonage pipe is fitted
A. At the end of septic tanks
B. On manholes
C. With a W.'trap
D. At the beginning of sewer line
Question 171
The most dangerous pollutant in vehicular emissions is
A. CO₂
B. SO₂
C. CO₂
D. O₂
Question 172
The moisture content of sludge is reduced from 90% to 80% in a sludge digestion tank. The percentage decrease in the volume of sludge, is
A. 25 %
B. 50 %
C. 10 %
D. 5 %
Question 173
The detention time of a circular tank of diameter d and water depth H, for receiving the sewage Q per hour, is
A. d² (0.011d + 0.785H)/Q
B. d (0.022d + 0.085H)/Q
C. d (0.785d + 0.011H)/Q
D. d (0.285d + 0.011H)/Q
Question 174
The design period in years for pumping plants, is
A. 1
B. 2 to 3
C. 3 to 5
D. 5 to 10
Question 175
At the junction of sewers
A. Top of smaller sewer is kept lower
B. Top of larger sewer is kept lower
C. Tops of both the sewers are at the same level
D. None of these
Question 176
The water carried sewerage system removes
A. Domestic sewage
B. Industrial sewage
C. Storm sewage
D. All the above
Question 177
The most effective arrangement for diverting excess storm water into a natural drainage, is
A. Leaping weir
B. Overflow weir
C. Siphon spill way
D. None of these
Question 178
Imhoff cone is used to determine
A. Settleable solids
B. Suspended solids
C. Dissolved solids
D. None of these
Question 179
For the survival of fish in a river stream, the minimum dissolved oxygen is prescribed
A. 3 ppm
B. 4 ppm
C. 5 ppm
D. 10 ppm
Question 180
The algae dies out in the zone of
A. Degradation
B. Active decomposition
C. Recovery
D. Cleaner water
Question 181
For detecting the nitrates in sewage, the colour may be developed by adding
A. Potassium permanganate
B. Sulphuric acid and napthamine
C. Phenol-di -sulphuric acid and potassium hydroxide
D. None of these
Question 182
Rate of flow of sewage is generally assumed
A. More than the rate of water supply
B. Equal to the rate of water supply
C. Less than the rate of water supply
D. At 150 litres per capita
Question 183
For detecting the nitrites in the sewage, the matching colour may be developed by adding
A. Potassium permanganate
B. Sulphuric acid and napthamine
C. Phenol-di -sulphuric acid potassium hydroxide
D. None of these
Question 184
The average temperature of sewage in India, is
A. 10°C
B. 15°C
C. 20°C
D. 25°C
Question 185
Fresh sewage is generally
A. Alkaline
B. Acidic
C. Highly decomposed
D. A source of objectionable odour
Question 186
House connections to the laterals is generally made by
A. R.C.C.
B. P.C.C.
C. Cast iron
D. Glazed stonewares
Question 187
The sewage is pumped up
A. From low lying areas
B. From flat areas
C. From basements
D. All the above
Question 188
The self-cleansing velocity of water flowing through pipe lines, is
A. 2 metres/sec
B. 1 metre/sec
C. 0.5 metre/sec
D. 0.25 metre/sec
Question 189
The dimensions of a rectangular settling tank are: length 24 m, width 6 m and depth 3 m. If 2 hour detention period for tanks is recommended, the rate of flow of sewage per hour, is
A. 204 cu.m
B. 208 cu.m
C. 212 cu.m
D. 216 cu.m
Question 190
Bottom openings 15 cm × 15 cm in the standing baffle wall are provided
A. 15 cm c/c
B. 22.5 cm c/c
C. 30 cm c/c
D. 50 cm c/c
Question 191
Which of the following pumps in used to pump sewage solids with liquid sewage without clogging the pump is?
A. Centrifugal pump
B. Pneumatic ejector
C. Reciprocating pump
D. None of these
Question 192
Ventilating shafts are provided to a sewer line at every
A. 100 m
B. 150 m
C. 200 m
D. 300 m
Question 193
The gradient of sewers depends upon
A. Velocity of flow
B. Diameter of the sewer
C. Discharge
D. All the above
Question 194
The width of a rectangular sewer is twice its depth while discharging 1.5 m/sec. The width of the sewer is
A. 0.68 m
B. 0.88 m
C. 1.36 m
D. 1.76 m
Question 195
The laying of sewers is done with
A. Magnetic compass
B. Theodolite
C. Level
D. Clinometer
Question 196
Pick up the correct statement from the following:
A. The boning rod is used for checking the levels of the sewer inverts
B. Manhole covers are made circular for the convenience of the cleaning staff
C. A manhole is classified as shallow manhole if its depth is less than 0.9 m
D. All the above
Question 197
For a grit chamber, if the recommended velocity of flow is 0.2 m/sec and detention period is 2 minutes, the length of the tank, is
A. 16 m
B. 20 m
C. 24 m
D. 30 m
Question 198
Pick up the correct statement from the following:
A. The circular section of sewers provides maximum hydraulic mean depth
B. The circular sewers are provided for separate sewerage system
C. The circular sewers work efficiently if the sections run at least half full
D. All the above
Question 199
The sewer which received discharge from two or more main sewers, is known as
A. A trunk sewer
B. An outfall sewer
C. A main sewer
D. An intercepting sewer
Question 200
If is the diameter of upper circular portion, the overall depth of a standard egg shaped section, is
A. 1.15 D
B. 1.25 D
C. 1.5 D
D. 1.75 D
Question 201
If q is the average sewage flow from a city of population P, the maximum sewage flow
A. Q = [(4 + )/(18 + )] q
B. Q = [(18 + P)/(4 + )] q
C. Q = [(18 + )/(4 + )] q
D. Q = [(5 + )/((15 + )] q
Question 202
Fresh sewage may become stale in
A. One hour
B. Two to three hours
C. Three to four hours
D. Six hours
Question 203
For a peak discharge of 0.0157 cumec, with a velocity of 0.9 m/sec, the diameter of the sewer main, is
A. 10 cm
B. 12 cm
C. 15 cm
D. 18 cm
Question 204
The grit and silt of the grit chambers, may not be used for
A. Raising low lying areas by dumping
B. Concreting
C. Both A and B
D. Neither A nor B
Question 205
When drainage to sewage ratio is 20, the peak dry weather flow is
A. 20% of the design discharge
B. Slightly less than 5% of the design discharge
C. Slightly more than 5% of the design discharge
D. None of these
Question 206
The sewerage system consists of
A. House sewer
B. Lateral sewer
C. Branch sewer
D. All of these
Question 207
For providing an Indian type W.C., the R.C.C. slabs in the toilet portion
A. Should be sunk by 20 cm
B. Should be kept 20 cm above the adjacent portion
C. Should be sunk by 50 cm
D. Need not be sunk
Question 208
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
A. D/1
B. D/2
C. D/3
D. D/4
Question 209
Hydraulic mean radius is
A. Mean radius of sewer
B. Difference in heads between two points in circular pipes
C. Mean of radii in a pipe line of varying cross -sections
D. Cross-sectional area/wetted perimeter
Question 210
Hazen’s formula VS = 418 (GS – Gw)d [(3T + 70)/100] is used for the settlement velocity of the particles of diameter
A. Less than 0.01 mm
B. Less than 0.05 mm
C. Less than 0.1 mm
D. Greater than 0.1 mm
Question 211
The sewer which resists sulphide corrosion, is
A. Brick sewer
B. Cast iron sewer
C. R.C. sewer
D. Lead sewer
Question 212
The arrangement made for passing the sewer line below an obstruction below the hydraulic gradient lines called
A. Inverted syphon
B. Depressed sewer
C. Sag pipe
D. all of these
Question 213
No treatment of the sewage is given if dilution factor is
A. Less than 150
B. Between 150 to 200
C. Between 200 to 300
D. More than 500
Question 214
In septic tanks,
A. Free board of 0.3 m may be provided
B. The baffles or tees are extended up to top level of scum
C. The clear space between the baffle top and covering slab is about 7.5 cm
D. All the above
Question 215
The maximum diameter of sewers adopted in the designs is
A. 1.0 m
B. 2.0 m
C. 3.0 m
D. 4.0 m
Question 216
Which one of the following part of human body withstands minimum radiation?
A. Thyroid
B. Kidneys
C. Eyes
D. Ovaries/testis
Question 217
In a sludge tank, the gas mainly produced, is
A. Oxygen
B. Nitrogen
C. Hydrogen
D. Carbon dioxide
Question 218
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
A. 100
B. 1000
C. 5000
D. 10000
Question 219
The gas which may cause explosion in sewers, is
A. Carbondioxide
B. Methane
C. Ammonia
D. Carbon monoxide
Question 220
Sludge banks are formed if sewage is disposed of in
A. Rivers
B. Seas
C. Lakes
D. None of these
Question 221
The rate of accumulation of sludge in septic tanks is recommended as
A. 30 litres/person/year
B. 25 litres/person/year
C. 30 litres/person/month
D. 25 litres/person/month
Question 222
In SI units the power of sound is represented in
A. Kgs
B. Joules
C. Newtons
D. Watts
Question 223
Disposal to sewage in large cities, is done in
A. Irrigation
B. Dilution
C. Oxidation
D. Purification
Question 224
A well oxidized sewage contains nitrogen mainly as
A. Nitrates
B. Nitrites
C. Free ammonia
D. None of these
Question 225
The settlement of a particle in sedimentation tank, is affected by
A. Velocity of flow
B. Viscosity of water
C. Size and shape of solid
D. All the above
Question 226
Skimming tanks are
A. Used to remove the grease and oil
B. Those from which sludge is skimmed out
C. Tanks provided with self- cleansing screens
D. Improved version of grit chambers
Question 227
‘Cowl’ is provided at
A. Lower end of ventilating column
B. Upper end of ventilating column
C. Upper end of the manhole
D. First step in manhole
Question 228
The formula V = (1/n) r2/3
A. Chezy’s formula
B. Bazin’s formula
C. Kutter’s formula
D. Manning’s formula
Question 229
A drop manhole is provided if
A. A sewer drops from a height
B. A branch sewer joins the main sewer at higher level
C. A lamp is inserted to check obstruction
D. None of these
Question 230
The most widely used pump for lifting sewage is
A. Centrifugal pump
B. Reciprocating pump
C. Pneumatic ejector
D. Air pressure pump
Question 231
The non-clog pump which permits solid matter to pass out with the liquid sewage, is
A. Centrifugal pump
B. Reciprocating pump
C. Pneumatic ejector
D. None of these
Question 232
The grit chambers of sewage treatment plants, are generally cleaned after
A. 2 days
B. 7 days
C. 12 days
D. 14 days
Question 233
Cement concrete sewers are only suitable if non-scouring velocity is between
A. 2.5 to 3.0 m/sec
B. 3.0 to 4.0 m/sec
C. 3.5 to 4.5 m/sec
D. 4.5 to 5.5 m/sec
Question 234
Pick up the correct statement from the following:
A. Maximum daily flow = 2 times the average daily flow
B. Maximum daily flow = ⅔ × average daily flow
C. Sewers are designed for minimum permissible velocity at minimum flow
D. All the above
Question 235
Pick up the correct statement from the following:
A. Small sewers are cleaned by flushing
B. Medium sewers are cleaned by cane rodding
C. Medium sewers may be cleaned by pills
D. All the above
Question 236
In sewers the velocity of flow should not be
A. More than the self-cleansing velocity
B. Less than the self-cleansing velocity
C. Less than 10 m/sec
D. More than 20 m/sec
Question 237
Which one of the following resists hydrogen sulphide corrosion?
A. R.C.C.
B. Glazed stone wares
C. Asbestos cement
D. Glazed ware
Question 238
The gas evolved in sewers is
A. Carbondioxide
B. Hydrogen sulphide
C. Methane
D. All of these
Question 239
The ratio of the diameter of a circular section and the side of a square section hydraulically equivalent, is
A. 1.095
B. 1.085
C. 1.075
D. 1.065
Question 240
Pick up the correct statement from the following:
A. The sewer pipes of sizes less than 0.4 m diameter are designed as running full at maximum discharge
B. The sewer pipes of sizes greater than 0.4 m diameter are designed as running 2/3rd or 3/4th full at maximum discharge
C. The minimum design velocity of sewer pipes is taken as 0.8 m/sec
D. All the above
Question 241
Pick up the correct statement from the following:
A. Anaerobic bacteria flourish in the absence of oxygen
B. Aerobic bacteria flourish in the presence of oxygen
C. Facultative bacteria flourish with or without oxygen
D. All the above
Question 242
The sewerage system originates from
A. House sewers
B. Lateral sewers
C. Branch sewers
D. Main sewers
Question 243
The digested sludge from septic tanks, is removed after a maximum period of
A. 3 years
B. 3.5 years
C. 4 years
D. 5 years
Question 244
The underground sewers are more subjected to
A. Tensile force
B. Compressive force
C. Bending force
D. Shearing force
Question 245
The formula which accepts the value of rugosity coefficient n = 0.012 to be used in Manning’s formula, is given by
A. Bazin
B. Crimp and Bruges
C. William-Hazen
D. Kutter
Question 246
¾th or ¼th extra space is left in sewer pipes at maximum discharge for
A. Low estimates of the average and maximum flows
B. Large scale infiltration of storm water
C. Unexpected increase in population
D. All the above
Question 247
In detritus tanks,
A. Flow velocity is kept 0.09 m/sec
B. Detention period is kept 3 to 4 minutes
C. Organic and inorganic materials are separated
D. All the above
Question 248
Kjeldahl nitrogen is a mixture of
A. Ammonia and nitrogen
B. Nitrogen and organic nitrogen
C. Organic nitrogen and ammonia
D. All the above
Question 249
The intensity of rain is expressed in
A. cm/minute
B. cm/hour
C. cm/day
D. None of these
Question 250
For sewers, inverted siphon is provided for
A. One pipe
B. Two pipes
C. Three pipes
D. Four pipes
Question 251
For large sewers, maximum distance between manholes may be
A. 50 m
B. 100 m
C. 200 m
D. 300 m
Question 252
In sewage, the solids in mg per litre is
A. 100 to 500
B. 500 to 1000
C. 1000 to 1500
D. 1500 to 2000
Question 253
For the COD test of sewage, organic matter is oxidised by K₂Cr₂O₇ in the presence of
A. H₂SO₄
B. HNO₃
C. HCl
D. None of these
Question 254
To test chemical oxygen demand (C.O.D.) of sewage, organic matter is oxidised by potassium dichromate in the presence of
A. Hydrochloric acid
B. Sulphuric acid
C. Nitric acid
D. Citric acid
Question 255
Pathogens (or pathogenic bacterias) in water may cause
A. Typhoid
B. Cholera
C. Dysentery
D. All the above
Question 256
Stone ware pipes are
A. Highly resistant to sulphide corrosion
B. Highly impervious
C. Hydraulically efficient because of their smooth interior surface
D. Especially suited to pressure pipes
Question 257
Pick up the correct statement from the following:
A. The ratio of the quantity of the diluting water to that of the sewage, is known as dilution factor
B. The automatic purification of polluted water, is known self purification phenomenon
C. The photosynthesis is carried out in the presence of sun light
D. All the above
Question 258
Pick up the correct statement from the following:
A. The water supply pipes carry pure water free from solid particles
B. The water supply pipes get clogged if flow velocity is less than self cleansing velocity
C. The sewers may be carried up and down the hills and valleys
D. The sewer pipes are generally laid along level hills
Question 259
An inverted siphon is designed generally for
A. One pipe
B. Two pipes
C. Three pipes
D. Four pipes
Question 260
In sewers the gas generally found, is
A. Hydrogen sulphide (H2S)
B. Carbon dioxide (CO2)
C. Methane (CH4)
D. All the above
Question 261
Sewer ventilating columns are generally placed at
A. Distances 150 m to 300 m
B. Upper ends of branch sewers
C. Every change in the size of sewers
D. All the above
Question 262
The coagulant which is generally not used for treating the sewage, is
A. Alum
B. Ferric chloride
C. Ferric sulphate
D. Chlorinated coppers
Question 263
Pick up the correct statement from the following:
A. Hydrogen sulphide gas in excess, may cause corrosion of concrete sewers
B. 4 ppm of Dissolved Oxygen (D.O.) is ensured before discharging the treated sewage in river
C. Solubility of oxygen in sewage is 95% of that of distilled water
D. All the above
Question 264
Pick up the correct statement from the following:
A. In treated sewage, 4 ppm of D.O. is essential
B. Only very fresh sewage contains some dissolved oxygen
C. The solubility of oxygen in sewage is 95% that is in distilled water
D. All the above
Question 265
In circular sewers if depth of flow is 0.2 times the full depth, the nominal gradient,
A. Is only provided
B. Is doubled
C. Is trebled
D. Is not enough
Question 266
The liquid wastes from kitchens, bath rooms and wash basins, is not called
A. Liquid waste
B. Sullage
C. Sewage
D. None of these
Question 267
If the diameter of a sewer is 100 mm, the gradient required for generating self cleansing velocity is
A. 1 in 60
B. 1 in 100
C. 1 in 120
D. None of these
Question 268
Self-cleansing velocity is
A. Velocity at dry weather flow
B. Velocity of water at flushing
C. Velocity at which no accumulation remains in the drains
D. Velocity of water in a pressure filter
Question 269
In a city the ratio of the drainage to sewage is 20, the percentage discharge passing through non-monsoon periods, is
A. 5
B. 10
C. 15
D. 20
Question 270
For design purposes, the normal rate of infiltration of ground water into the sewer, is
A. 500 litres/km/cm
B. 1000 litres/km/cm
C. 1500 litres/km/cm
D. 2000 litres/km/cm
Question 271
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
A. 100 cm
B. 90 cm
C. 80 cm
D. 50 cm
Question 272
In 1000 kg of sewage, the total solids approximate
A. 0.5 to 1.0 kg
B. 1 kg to 2.0 kg
C. 5 kg to 7.5 kg
D. 7.5 kg to 10 kg
Question 273
Pick up the incorrect statement from the following:
A. The process of decomposing the organic matter under controlled anaerobic conditions, is called sludge digestion
B. Sludge digestion is carried out in sludge tank
C. The gases produced in sludge digestion process, contain 75% carbon dioxide
D. The gases produced in sludge digestion process, contain 75% methane
Question 274
Pick up the correct statement from the following:
A. Turbidity is more in strong sewage
B. The black colour indicates septic sewage
C. The sewage omits offensive odours after four hours
D. All the above
Question 275
Dry water flow in a combined sewer, is
A. Industrial sewage
B. Domestic sewage
C. Storm water
D. Inclusive of domestic and industrial sewage but excludes storm water
Question 276
A sewer running partially full and hurried with back filled, fails in compression due to
A. Weight of the pipe
B. Weight of the back fill
C. Superimposed traffic loads
D. All the above
Question 277
The ratio of design discharge to the surface area of a sedimentation tank is called
A. Surface loading
B. Overflow rate
C. Overflow velocity
D. All of these
Question 278
The maximum depth of sedimentation tanks, is kept
A. 3 m
B. 3.5 m
C. 4 m
D. 4.5 m
Question 279
Chlorination of water is done for the removal of
A. Bacterias
B. Suspended solids
C. Sediments
D. Hardness
Question 280
Depletion of ozone layer in the outer atmosphere may cause
A. Lung cancer
B. Skin cancer
C. Bronchitis
D. Heart disorder
Question 281
For treating the sewage of a large city, you will recommend
A. A sedimentation tank and an activated sludge treatment plant
B. A plant consisting of Imhoff tanks with low rate trickling filters
C. Sedimentation tanks with high rate trickling filters
D. None of these
Question 282
In sewers the effect of scouring is more on
A. Top side
B. Bottom side
C. Horizontal side
D. All sides
Question 283
For estimating the peak run off the rational formula Q = 0.0278 KpA was evolved by
A. Kinchling
B. Lloyd Davis
C. Frubling
D. All the above
Question 284
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
A. 0.05552 cumec
B. 0.05554 cumec
C. 0.05556 cumec
D. 0.0556 cumec
Question 285
The settlement velocity of a solid (diameter 0.5 mm, specific gravity 1.75) in water having temperature 10°C, is
A. 213.5 cm/sec
B. 313.5 cm/sec
C. 413.5 cm/sec
D. 500 cm/sec
Question 286
For evaporation and measurement of settable solids, the apparatus used, is
A. A jar
B. A breaker
C. A test tube
D. An Imhoff cone
Question 287
As compared to fresh river water, sea water contains oxygen
A. 10% less
B. 20% less
C. 10% more
D. 20% more
Question 288
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
A. Full depth
B. Half full
C. Two third full
D. Three fourth full
Question 289
The settling velocity of a spherical particle of diameter less than 0.1 mm as per Stock’s law, is
A. Vs = 418 (Gs – Gw) d [(3T + 70)/100]
B. Vs = 418 (Gs – Gw)d² [(3T + 70)/100]
C. Vs = 218 (Gs – Gw)d² [(3T + 70)/100]
D. Vs = 218 (Gs – Gw)d [(3T + 70)/100]
Question 290
Sewer manholes are generally provided at
A. The change of gradient
B. The change of direction
C. The junctions of sewers
D. All of these
Question 291
Bio-chemical oxygen demand (BOD) for the first 20 days in generally referred to
A. Initial demand
B. First stage demand
C. Carbonaceous demand
D. All of these
Question 292
The asbestos cement pipes are generally laid
A. Horizontally
B. Vertically
C. At an angle of 30°
D. At an angle of 60°
Question 293
pH value of sludge during alkaline regression stage, is
A. More than 7
B. Less than 7
C. Less than 6
D. More than 6
Question 294
The small sewers are cleaned by
A. Flushing
B. Cane rodding
C. Wooden pills
D. None of these
Question 295
Design period of 40 to 50 years is adopted for
A. Branch sewers
B. Main sewers
C. Trunk sewers
D. All the above
Question 296
Setting out the alignments of sewers may start from
A. City
B. Out-fall
C. Tail end
D. Any point
Question 297
The rate of accumulation of sludge per person per year, is
A. 10 litres
B. 15 litres
C. 20 litres
D. 25 litres
Question 298
Lead acetate test in sewer manhole is done to test the presence of
A. Methane gas
B. Hydrogen sulphide
C. Carbondioxide gas
D. Diesel vapours
Question 299
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
A. 100 cm
B. 110 cm
C. 120 cm
D. 150 cm
Question 300
To maintain aerobic biological activity, the moisture content of the compost mass should be about
A. 45 %
B. 50 %
C. 55 %
D. 60 %
Question 301
A safety lamp when inserted in the upper portion of a manhole causes flames. It indicates the presence of
A. Carbondioxide gas
B. Hydrogen sulphide gas
C. Methane gas
D. Petrol vapours
Question 302
The sewers
A. Must be of adequate size to avoid over flow
B. Must flow under gravity ½ to ¾ full
C. Must be laid at least 2 to 3 m deep to collect /water from the basements
D. All the above
Question 303
Pick up the incorrect statement from the following for allowing workers to enter sewers
A. The particular manhole and one manhole on upstream and one manhole on downstream should remain open for 30 minutes
B. Proper tests for the presence of poisonous gases must be carried out
C. The men entering the manhole should be advised to smoke in the sewer
D. Warning signals should be erected
Question 304
The normal values of over flow rates for sedimentation tanks using coagulant, ranges between
A. 25,000 to 35,000 litres/sqm/day
B. 40,000 to 50,000 litres/sqm/day
C. 50,000 to 60,000 litres/sqm/day
D. 80,000 to 100,000 litres/sqm/day
Question 305
Imhoff cone is used to measure
A. Total organic solids
B. Total solids
C. Total in organic solids
D. Settleable solids
Question 306
The normal values of over flow rates for secondary sedimentation tanks, ranges between
A. 25,000 to 35,000 litres/sqm/day
B. 40,000 to 50,000 litres/sqm/day
C. 50,000 to 60,000 litres/sqm/day
D. 80,000 to 10,000 litres/sqm/day
Question 307
The detention period for plain sedimentation water tanks, is usually
A. 4 to 8 hours
B. 8 to 16 hours
C. 16 to 24 hours
D. 24 to 36 hours
Question 308
The normal value of over flow rates for plain primary sedimentation tanks, ranges between
A. 25,000 to 35,000 litres/sqm/day
B. 40,000 to 50,000 litres/sqm/day
C. 50,000 to 60,000 litres/sqm/day
D. 80,000 to 100,000 litres/sqm/day
Question 309
The screens are fixed
A. Perpendicular to the direction of flow
B. Parallel to the direction of flow
C. At an angle 30° to 60° to the direction of flow
D. None of these
Question 310
The minimum recommended diameter of sewers, is
A. 5 cm
B. 10 cm
C. 15 cm
D. 20 cm
Question 311
In case of sewer lines
A. Water test is carried out to check water tightness of the joints
B. Test for straightness is carried out with the help of a lamp and mirror
C. Obstruction test is carried out with the help of smooth ball of diameter 13 mm
D. All the above
Question 312
The pH value of fresh sewage is usually
A. Equal to 7
B. More than 7
C. Less than 7
D. Equal to zero
Question 313
In septic tanks, decomposition of organic bacteria, is done by
A. Anaerobic bacteria
B. Aerobic bacteria
C. Both types of bacterias
D. None of these
Question 314
If is the diameter of upper circular portion, the overall depth of New Egg shaped sewer section, is
A. 1.250 D
B. 1.350 D
C. 1.425 D
D. 1.625 D
Question 315
If the diameter of sewer is 225 mm, the gradient required for generating self cleansing velocity, is
A. 1 in 60
B. 1 in 100
C. 1 in 120
D. None of these
Question 316
Pick up the correct statement from the following:
A. Rate of digestion of sludge is more at higher temperature
B. Thermophilic organisms digest the sludge if the temperature ranges from 40° to 60°C
C. Mesophilic organisms digest the sludge if the temperature is between 25° and 40°C
D. All the above
Question 317
If the diameter of a sewer is 150 mm, the gradient required for generating self cleansing velocity, is
A. 1 in 60
B. 1 in 100
C. 1 in 120
D. None of these
Question 318
Pick up the incorrect size of stone ware sewers
A. 52.5 cm
B. 67.5 cm
C. 82.5 cm
D. None of these
Question 319
Pick up the incorrect statement from the following:
A. Septic tanks are horizontal continuous flow type of sedimentation tanks
B. Septic tanks are generally provided a detention period of 12 to 36 hours
C. Septic tanks are completely covered and high vent shafts are provided for the escape of foul gases
D. None of these
Question 320
The stone ware sewers
A. Are used for carrying sewage and drainage from houses
B. Are manufactured from clays and shale
C. After casting are dried and burnt at temperature 150°C, 700°C and 1200°C
D. All the above
Question 321
The angle subtended by the surface of sewer water with partial flow, at sewer centre is 120°, the depth of sewerage is
A. 20 cm
B. 25 cm
C. 40 cm
D. 50 cm
Question 322
Pick up the correct statement from the following:
A. The materials separated by screens, is called screenings
B. The screenings are disposed off either by burning or by burial or by dumping
C. The process of burning the screenings, is known as compositing
D. All the above
Question 323
depends upon The Chezy’s constant C in the formula V = C
A. Size of the sewer
B. Shape of the sewer
C. Roughness of sewer surface
D. All the above
Question 324
Pick up the correct statement from the following:
A. The maximum rate of storm runoff is called peak drainage discharge
B. Rational method of estimating peak run off, may be used precisely for areas less than 50 hectares
C. The period after which the entire area starts contributing to the runoff, is called the time of concentration
D. All the above
Question 325
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
A. 2 hours
B. 3 hours
C. 4 hours
D. 5 hours
Question 326
Primary treatment of sewage consists of removal of
A. Large suspended organic solids
B. Oil and grease
C. Sand and girt
D. Floating materials
Question 327
For efficient working of a sewer, it must be ensured that
A. Minimum velocity of 0.45 m/sec, is maintained at its minimum flow
B. A maximum velocity of 0.90 m/sec, is maintained at its maximum flow
C. Both (A) and (B)
D. Neither (A) nor (B)
Question 328
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
A. 2 hours
B. 4 hours
C. 6 hours
D. 8 hours
Question 329
In olden days the type of section adopted in trunk and out fall sewers was
A. Parabolic shaped
B. Horse shoe shaped
C. Egg shaped
D. Circular shaped
Question 330
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
A. 1 in 100 upward
B. 1 in 500 upward
C. 1 in 100 downward
D. 1 in 503 upward
Question 331
The sewer which collects the discharge from a collecting system and delivers it to a treatment plant, is known
A. House sewer
B. Lateral sewer
C. Branch sewer
D. Sewer outfall
Question 332
The sewer pipes
A. Carry sewage as gravity conduits
B. Are designed for generating self-cleansing velocities at different discharge
C. Should resist the wear and tear caused due to abrasion
D. All the above
Question 333
The detention time (t) of a settling tank, may be defined as the time required for
A. A particle to travel along its length
B. A particle to travel from top surface to bottom sludge zone
C. The flow of sewage to fill the tank
D. None of these
Question 334
Which one of the following tests is used for testing sewer pipes?
A. Water test
B. Ball test
C. Mirror test
D. All of these
Question 335
Pick up the correct statement from the following:
A. The larger the sewer in size, more will be velocity
B. The smaller the sewer in size, less will be velocity
C. The larger the sewer in size, no deposition will take place
D. The larger the sewer in size, deposition will take place
Question 336
Pick up the incorrect statement from the following:
A. The mixture of water and waste products, is called sewage
B. The treated sewage effluents, are generally used for irrigating the crops
C. The process of collecting, treating and disposing off the sewage, is called sewerage
D. The old convergence system was definitely better than water carried sewerage system
Question 337
Aerobic activity is maximum
A. In freshly produced sewage
B. At sewer pipes
C. In sewer treatment plants
D. None of these
Question 338
During preliminary treatment of a sewage
A. Oil and grease are removed from skimming tanks
B. Floating materials are removed by screening
C. Girt and sand are removed by girt chambers
D. All the above
Question 339
Boussinesq’s equation for ascertaining unit pressure at a depth on sewers due to traffic loads, is
A. pt = 3H3p/2 Z5
B. pt = 2H3p/3 Z5
C. pt = 3H3p/2 Z5
D. pt = 2H3p/3 Z5
Question 340
Traps
A. Are water seals which prevent the entry of foul gases
B. Are used to trap the rats entering sewers
C. Dissolve the foul gases
D. Create symphonic action to increase the quick disposal of sewerage
Question 341
In sewage having fully oxidised organic matter, the nitrogen exists in the form of
A. Nitrites
B. Nitrates
C. Free ammonia
D. Aluminoid nitrogen
Question 342
In sewers the highest non-scouring velocity is achieved in
A. Glazed bricks sewers
B. Cast iron sewers
C. Cement concrete sewers
D. Stone ware sewers
Question 343
If the pH value of sewage is 7
A. It is acidic
B. It is alkaline
C. It is neutral
D. None of these