280+ Water and Wastewater Engineering Solved MCQs

1.

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
Answer» D. All the above
2.

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
Answer» D. All the above
3.

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)
Answer» C. Both (a) and (b)
4.

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
Answer» B. 22.5 cm c/c
5.

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
Answer» B. Smoke test
6.

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
Answer» D. All the above
7.

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
Answer» D. More than 500
8.

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
Answer» A. Centrifugal pump
9.

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
Answer» D. 90 days
10.

The coagulant which is generally not used for treating the sewage, is

A. Alum
B. Ferric chloride
C. Ferric sulphate
D. Chlorinated copperas
Answer» A. Alum
11.

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
Answer» C. Windrow
12.

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
Answer» C. Methane
13.

The gas which may cause explosion in sewers, is

A. Carbondioxide
B. Methane
C. Ammonia
D. Carbon monoxide
Answer» B. Methane
14.

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
Answer» C. The gases produced in sludge digestion process, contain 75% carbon dioxide
15.

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
Answer» D. All the above
16.

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
Answer» D. 2 hours
17.

The Chezy's constant C in the formula V = C 𝑟𝑠 depends upon

A. Size of the sewer
B. Shape of the sewer
C. Roughness of sewer surface
D. All the above
Answer» D. All the above
18.

To prevent settling down of sewage both at the bottom and on the sides of a large sewer, selfcleaning 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
Answer» D. 0.75 m/sec
19.

Assertion (A): The determination of pH value of sewerage is important. Reason (R): The efficiency of certain treatment methods depends upon the availability of pH value.

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
Answer» A. Both A and R are true and R is the correct explanation of A
20.

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
Answer» C. 50,000 to 60,000 litres/sqm/day
21.

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
Answer» D. All the above
22.

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
Answer» D. Water supply allowance per capita
23.

If q is the average sewage flow from a city of population P, the maximum sewage flow

A. Q = [(4 + 𝑝 )/(18 + 𝑝 )] q
B. Q = [(18 +p )/(4 + 𝑝 )] q
C. Q = [(18 + 𝑝 )/(4 + 𝑝 )] q
D. Q = [(5 + 𝑝 )/(15 + 𝑝 )] q
Answer» D. Q = [(5 + 𝑝 )/(15 + 𝑝 )] q
24.

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
Answer» B. Carbon dioxide
25.

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
Answer» D. Cross-sectional area/wetted perimeter
26.

If the depth of flow in a circular sewer is 1/4th of its diameter D, the wetted perimeter is

A. 𝝅𝑫𝟐
B. 𝝅𝑫𝟒
C. 𝝅𝑫𝟑
D. 𝝅𝑫
Answer» C. 𝝅𝑫𝟑
27.

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
Answer» D. None of these
28.

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
Answer» B. Trickling filters
29.

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
Answer» A. A trunk sewer
30.

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)
Answer» B. Concreting
31.

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
Answer» A. A sedimentation tank and an activated sludge treatment plant
32.

Imhoff cone is used to measure

A. Total organic solids
B. Total solids
C. Total in organic solids
D. Settleable solids
Answer» D. Settleable solids
33.

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
Answer» D. Both (a) and (c) of above
34.

For the COD test of sewage, organic matter is oxidised by K2 Cr2O7 in the presence of

A. H2SO4
B. HNO3
C. HCl
D. None of these
Answer» A. H2SO4
35.

The sludge does not contain waste water from

A. Bath rooms
B. Wash basins
C. Kitchen sinks
D. Toilets
Answer» D. Toilets
36.

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
Answer» B. Less than the self-cleansing velocity
37.

In sewers the effect of scouring is more on

A. Top side
B. Bottom side
C. Horizontal side
D. All sides
Answer» B. Bottom side
38.

The sewer which resists sulphide corrosion, is

A. Brick sewer
B. Cast iron sewer
C. R.C.C. sewer
D. Lead sewer
Answer» D. Lead sewer
39.

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)
Answer» D. Q/(B × L)
40.

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
Answer» B. Crimp and Bruges
41.

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
Answer» B. Dissolved Oxygen (D.O.)
42.

Water content of sewage is about

A. 90 %
B. 95 %
C. 99 %
D. 9.9 %
Answer» D. 9.9 %
43.

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
Answer» A. Used to remove the grease and oil
44.

The most efficient cross-section of sewers in a combined sewerage system is

A. ) Parabolic
B. Circular
C. Rectangular
D. New egged
Answer» B. Circular
45.

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
Answer» A. 4 to 8 hours
46.

The factor responsible for purification of sewage in river is

A. Hydrology
B. Dissolved oxygen in water
C. Temperature
D. All the above
Answer» D. All the above
47.

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)
Answer» D. Both (B) and (C)
48.

To maintain aerobic biological activity, the moisture content of the compost mass should be about

A. 45 %
B. 50 %
C. 55 %
D. 60 %
Answer» C. 55 %
49.

Pick up the correct statement from the following:

A. The larger the sewer in size, more will be
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
Answer» D. The larger the sewer in size, deposition will take place
50.

The pH value of sewage is determined with the help of

A. Imhoff Cone
B. Turbid meter
C. Potentiometer
D. None of these
Answer» C. Potentiometer
51.

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
Answer» B. 40,000 to 50,000 litres/sqm/day
52.

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
Answer» D. The depth of tank is kept equal to its width
53.

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
Answer» C. Separate system
54.

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
Answer» A. 30 litres/person/year
55.

Dried sewage after treatment is used as

A. Fertilizer
B. Building material
C. Chemical for lowering B.O.D.
D. Base material for paints
Answer» A. Fertilizer
56.

For drains up to 15 cumecs, the depth “d” and “B” width are related by

A. d = 0.2
B. d = 0.5 B
C. B = 0.2 d
D. B = 0.5 d
Answer» B. d = 0.5 B
57.

In areas where light rains are uniformly distributed throughout the year, the type of sewerage system to be adopted is

A. Separate system
B. Combined system
C. Partially combined system
D. None of these
Answer» B. Combined system
58.

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
Answer» C. Velocity at which no accumulation remains in the drains
59.

5 days-biochemical oxygen demand (BOD5) is taken at a temperature of

A. 0°C
B. 15°C
C. 20°C
D. 25°C
Answer» C. 20°C
60.

A well oxidized sewage contains nitrogen mainly as

A. Nitrates
B. Nitrites
C. Free ammonia
D. None of these
Answer» A. Nitrates
61.

In a sludge tank, the gas mainly produced, is

A. Oxygen
B. Nitrogen
C. Hydrogen
D. Carbon dioxide
Answer» D. Carbon dioxide
62.

If “D” 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
Answer» D. 1.625 D
63.

In normal conditions, the period for sludge digestion, is

A. 10 days
B. 20 days
C. 30 days
D. 60 days
Answer» C. 30 days
64.

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
Answer» D. An Imhoff cone
65.

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%
Answer» C. 60 to 80%
66.

For design of sewers, percentage of sewage discharge is assumed

A. 65 to 70
B. 70 to 75%
C. 75 to 80%
D. 85%
Answer» C. 75 to 80%
67.

The grit chambers of sewage treatment plants, are generally cleaned after

A. 2 days
B. 7 days
C. 12 days
D. 14 days
Answer» D. 14 days
68.

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)
Answer» C. Both (a) and (b)
69.

The average temperature of sewage in India, is

A. 10°C (B) (C) (D)
B. 15°C
C. 20°C
D. 25°C
Answer» C. 20°C
70.

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
Answer» C. Inlets are generally provided in all sewers
71.

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) (C) (D)
B. 50 %
C. 10 %
D. 5 %
Answer» B. 50 %
72.

If ‘D’ 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
Answer» D. 1.625 D
73.

In trickling filter, B.O.D. is reduced to

A. 30 to 40% (B) (C) (D)
B. 40 to 60%
C. 60 to 80%
D. 80 to 90%
Answer» C. 60 to 80%
74.

For design of sewers, percentage of sewage discharge is assumed

A. 65 to 70% (B) (C) (D)
B. 70 to 75%
C. 75 to 80%
D. 85%
Answer» C. 75 to 80%
75.

The grit chambers of sewage treatment plants, are generally cleaned after

A. 2 days (B) (C) (D)
B. 7 days
C. 12 days
D. 14 days
Answer» D. 14 days
76.

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
Answer» B. Aeration is done with an admixture of previously aerated sludge
77.

For detecting the nitrates in sewage, the colour may be developed by adding

A. Potassium permanganate (B) (C) (D)
B. Sulphuric acid and napthamine
C. Phenol-di-sulphuric acid and potassium hydroxide
D. None of these
Answer» C. Phenol-di-sulphuric acid and potassium hydroxide
78.

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]
Answer» B. Vs = 418 (Gs - Gw)d² [(3T + 70)/100]
79.

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
Answer» D. 150 m to 300 m
80.

Stone ware pipes are

A. Highly resistant to sulphide corrosion (B) (C) (D)
B. Highly impervious
C. Hydraulically efficient because of their smooth interior surface
D. Especially suited to pressure pipes
Answer» D. Especially suited to pressure pipes
81.

The intensity of rain is expressed in

A. cm/minute (B) (C) (D)
B. cm/hour
C. cm/day
D. None of these
Answer» B. cm/hour
82.

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
Answer» A. 1.095
83.

Which one of the following part of human body withstands minimum radiation?

A. Thyroid
B. Kidneys
C. Eyes
D. Ovaries/testis
Answer» D. Ovaries/testis
84.

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
Answer» D. Having drains at different levels
85.

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
Answer» B. 1 in 10
86.

Primary treatment of sewage consists of removal of

A. Large suspended organic solids
B. Oil and grease
C. Sand and girt
D. Floating materials
Answer» A. Large suspended organic solids
87.

Cement concrete sewers are only suitable if non-scouring velocity is between

A. ) 2.5 to 3.0 m/sec (B) (C) (D)
B. 3.0 to 4.0 m/sec
C. 3.5 to 4.5 m/sec
D. 4.5 to 5.5 m/sec
Answer» A. ) 2.5 to 3.0 m/sec (B) (C) (D)
88.

The most widely used pump for lifting sewage is

A. Centrifugal pump
B. Reciprocating pump
C. Pneumatic ejector
D. Air pressure pump
Answer» A. Centrifugal pump
89.

Setting out the alignments of sewers may start from

A. City
B. Out-fall
C. Tail end
D. Any point
Answer» C. Tail end
90.

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
Answer» A. d² (0.011d + 0.785H)/Q
91.

Lead acetate test in sewer manhole is done to test the presence of

A. Methane gas (B) (C) (D)
B. Hydrogen sulphide
C. Carbondioxide gas
D. Diesel vapours
Answer» B. Hydrogen sulphide
92.

Anti syphonage pipe is fitted

A. At the end of septic tanks (B) (C) (D)
B. On manholes
C. With a W.C. trap
D. At the beginning of sewer line
Answer» C. With a W.C. trap
93.

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
Answer» D. All the above
94.

The ratio of maximum sewage flow to average sewage flow for mains up to 1 m in diameter, is

A. 1.5 (B) (C) (D)
B. 2.0
C. 3.0
D. 4.0
Answer» B. 2.0
95.

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
Answer» A. More than 7
96.

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
Answer» D. all of these
97.

Pick up the incorrect size of stone ware sewers

A. 52.5 cm (B) (C) (D)
B. 67.5 cm
C. 82.5 cm
D. None of these
Answer» D. None of these
98.

Chlorination of water is done for the removal of

A. Bacterias
B. Suspended solids
C. Sediments
D. Hardness
Answer» A. Bacterias
99.

Sludge banks are formed if sewage is disposed of in

A. Rivers
B. Seas
C. Lakes
D. None of these
Answer» B. Seas
100.

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
Answer» D. Circular Imhoff double storey tanks without bottom hoppers
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