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Waste Water Engineering MCQ Questions & Answers

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

Chlorination of water is done for the removal of

A. Bacterias
B. Suspended solids
C. Sediments
D. Hardness

View Answer

Question 2

The factor responsible for purification of sewage in river is

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

View Answer

Question 3

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

View Answer

Question 4

Discrete or granular particles change their

A. Size
B. Shape
C. Weight
D. None of these

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Question 5

The sewage treatment in septic tanks is due to

A. Anaerobic decomposition
B. Aerobic decomposition
C. Parasitic decomposition
D. None of these

View Answer

Question 6

Lead caulked joints are used for laying

A. Stone ware pipes
B. Earthenware pipes
C. C.I. pipes
D. G.I. pipes

View Answer

Question 7

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.

View Answer

Question 8

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

View Answer

Question 9

The average temperature of sewage in India, is

A. 10°C
B. 15°C
C. 20°C
D. 25°C

View Answer

Question 10

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

View Answer

Question 11

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

View Answer

Question 12

The most widely used pump for lifting sewage is

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

View Answer

Question 13

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

View Answer

Question 14

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

View Answer

Question 15

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

View Answer

Question 16

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

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Question 17

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

View Answer

Question 18

In sewage having fully oxidised organic matter, the nitrogen exists in the form of

A. Nitrites
B. Nitrates
C. Free ammonia
D. Aluminoid nitrogen

View Answer

Question 19

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.

View Answer

Question 20

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.

View Answer

Question 21

The intensity of rain is expressed in

A. cm/minute
B. cm/hour
C. cm/day
D. None of these

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Question 22

The first stage of neutral process of sludge digestion, is

A. Acid fermentation
B. Acid regression
C. Alkaline fermentation
D. None of these

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Question 23

Depletion of ozone layer in the outer atmosphere may cause

A. Lung cancer
B. Skin cancer
C. Bronchitis
D. Heart disorder

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Question 24

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

View Answer

Question 25

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

View Answer

Question 26

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

View Answer

Question 27

Sewer pipes need be checked for

A. Minimum flow
B. Maximum flow
C. Both A and B
D. None of these

View Answer

Question 28

A nuisance is experienced in diluting water if dilution factor is less than

A. 100
B. 60
C. 40
D. 20

View Answer

Question 29

A manhole is generally provided at each

A. Bend
B. Junction
C. Change of gradient
D. All the above

View Answer

Question 30

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

View Answer

Question 31

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

View Answer

Question 32

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

View Answer

Question 33

In normal conditions, the period for sludge digestion, is

A. 10 days
B. 20 days
C. 30 days
D. 60 days

View Answer

Question 34

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

View Answer

Question 35

The rate of accumulation of sludge per person per year, is

A. 10 litres
B. 15 litres
C. 20 litres
D. 25 litres

View Answer

Question 36

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

View Answer

Question 37

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

View Answer

Question 38

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

View Answer

Question 39

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

View Answer

Question 40

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

View Answer

Question 41

If the pH value of sewage is 7

A. It is acidic
B. It is alkaline
C. It is neutral
D. None of these

View Answer

Question 42

Fresh sewage may become stale in

A. One hour
B. Two to three hours
C. Three to four hours
D. Six hours

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Question 43

The sludge does not contain waste water from

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

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Question 44

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

A. Parabolic
B. Circular
C. Rectangular
D. New egged

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Question 45

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

View Answer

Question 46

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

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Question 47

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.

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Question 48

The sewage is pumped up

A. From low lying areas
B. From flat areas
C. From basements
D. All the above

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Question 49

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.

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Question 50

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

View Answer

Question 51

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.

View Answer

Question 52

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

View Answer

Question 53

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

View Answer

Question 54

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

View Answer

Question 55

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

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Question 56

The coagulant widely used for sewage treatment, is

A. alum
B. ferric chloride
C. ferric sulphate
D. chlorinated copperas.

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Question 57

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

View Answer

Question 58

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

View Answer

Question 59

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

View Answer

Question 60

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

View Answer

Question 61

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

View Answer

Question 62

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

View Answer

Question 63

In a fully mechanised composting plant, involves

A. mechanized receipt
B. mechanized segregation
C. mechanized pulverising of refuse
D. all of these.

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Question 64

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.

View Answer

Question 65

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.

View Answer

Question 66

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

View Answer

Question 67

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

View Answer

Question 68

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

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Question 69

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

View Answer

Question 70

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

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Question 71

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

View Answer

Question 72

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]

View Answer

Question 73

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 %

View Answer

Question 74

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.

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Question 75

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

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Question 76

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

View Answer

Question 77

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

View Answer

Question 78

Flocculated particles do not change their

A. Size
B. Shape
C. Weight
D. None of these

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Question 79

The design period in years for pumping plants, is

A. 1
B. 2 to 3
C. 3 to 5
D. 5 to 10

View Answer

Question 80

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

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Question 81

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

View Answer

Question 82

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

View Answer

Question 83

Disposal to sewage in large cities, is done in

A. Irrigation
B. Dilution
C. Oxidation
D. Purification

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Question 84

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

View Answer

Question 85

Which one of the following gases is most significant as air pollutant?

A. Carbondioxide
B. Oxygen
C. Nitrogen
D. Sulphur-dioxide

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Question 86

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

View Answer

Question 87

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

View Answer

Question 88

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

View Answer

Question 89

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

View Answer

Question 90

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

View Answer

Question 91

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

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Question 92

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

View Answer

Question 93

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

View Answer

Question 94

The algae dies out in the zone of

A. Degradation
B. Active decomposition
C. Recovery
D. Cleaner water

View Answer

Question 95

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

View Answer

Question 96

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

View Answer

Question 97

Aerobic activity is maximum

A. In freshly produced sewage
B. At sewer pipes
C. In sewer treatment plants
D. None of these

View Answer

Question 98

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

View Answer

Question 99

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

View Answer

Question 100

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

View Answer

Question 101

For house drainage minimum gradient is

A. 1 in 60
B. 1 in 80
C. 1 in 10
D. 1 in 400

View Answer

Question 102

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.

View Answer

Question 103

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

View Answer

Question 104

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

View Answer

Question 105

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.

View Answer

Question 106

The liquid wastes from kitchens, bath rooms and wash basins, is not called

A. Liquid waste
B. Sullage
C. Sewage
D. None of these

View Answer

Question 107

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

View Answer

Question 108

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

View Answer

Question 109

A well oxidized sewage contains nitrogen mainly as

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

View Answer

Question 110

Setting out the alignments of sewers may start from

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

View Answer

Question 111

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

View Answer

Question 112

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.

View Answer

Question 113

An inverted siphon is designed generally for

A. one pipe
B. two pipes
C. three pipes
D. four pipes.

View Answer

Question 114

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

View Answer

Question 115

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

View Answer

Question 116

In a fully mechanised composting plant, involves

A. Mechanized receipt
B. Mechanized segregation
C. Mechanized pulverising of refuse
D. All of these

View Answer

Question 117

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

View Answer

Question 118

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

View Answer

Question 119

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

View Answer

Question 120

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

View Answer

Question 121

Oxidation process results in the formation of

A. Carbon dioxide
B. Nitrates
C. Sulphates
D. All the above

View Answer

Question 122

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

View Answer

Question 123

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

View Answer

Question 124

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

View Answer

Question 125

For sewers, inverted siphon is provided for

A. One pipe
B. Two pipes
C. Three pipes
D. Four pipes

View Answer

Question 126

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

View Answer

Question 127

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

View Answer

Question 128

Chlorination of water is done for the removal of

A. bacterias
B. suspended solids
C. sediments
D. hardness.

View Answer

Question 129

Fresh sewage is generally

A. Alkaline
B. Acidic
C. Highly decomposed
D. A source of objectionable odour

View Answer

Question 130

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

View Answer

Question 131

Clogging of sewers, is caused due to

A. Silting
B. Low discharge
C. Greasy and oily matters
D. All the above

View Answer

Question 132

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

View Answer

Question 133

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

View Answer

Question 134

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

View Answer

Question 135

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

View Answer

Question 136

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

View Answer

Question 137

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

A. Alum
B. Ferric chloride
C. Ferric sulphate
D. Chlorinated coppers

View Answer

Question 138

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.

View Answer

Question 139

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

View Answer

Question 140

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

View Answer

Question 141

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

View Answer

Question 142

The pH value of sewage is determined with the help of

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

View Answer

Question 143

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

View Answer

Question 144

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.

View Answer

Question 145

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

View Answer

Question 146

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

View Answer

Question 147

Dried sewage after treatment is used as

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

View Answer

Question 148

The minimum diameter of sewer to be adopted is

A. 10 cm
B. 12.5 cm
C. 15 cm
D. 25 cm

View Answer

Question 149

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

A. 0°C
B. 15°C
C. 20°C
D. 25°C

View Answer

Question 150

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%

View Answer

Question 151

The suitable cross-section of sewers to carry combined flow, is

A. Circular
B. Egg shaped
C. Rectangular
D. Horse shoe shaped

View Answer

Question 152

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

View Answer

Question 153

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

View Answer

Question 154

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

View Answer

Question 155

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

View Answer

Question 156

R.M.O. expenses include

A. Running expenses
B. Maintenance expenses
C. Operation expenses
D. All the above

View Answer

Question 157

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

View Answer

Question 158

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

View Answer

Question 159

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

View Answer

Question 160

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

View Answer

Question 161

Ventilating shafts are provided to a sewer line at every

A. 100 m
B. 150 m
C. 200 m
D. 300 m

View Answer

Question 162

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

View Answer

Question 163

‘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

View Answer

Question 164

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

View Answer

Question 165

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

View Answer

Question 166

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

View Answer

Question 167

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

View Answer

Question 168

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

View Answer

Question 169

The asbestos cement pipes are generally laid

A. Horizontally
B. Vertically
C. At an angle of 30°
D. At an angle of 60°

View Answer

Question 170

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

View Answer

Question 171

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

View Answer

Question 172

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

View Answer

Question 173

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

View Answer

Question 174

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

View Answer

Question 175

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

View Answer

Question 176

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

View Answer

Question 177

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.

View Answer

Question 178

Removal of oil and grease from sewage, is known

A. Screening
B. Skimming
C. Filtration
D. None of these

View Answer

Question 179

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

View Answer

Question 180

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

View Answer

Question 181

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

View Answer

Question 182

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

View Answer

Question 183

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

View Answer

Question 184

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

View Answer

Question 185

The most dangerous pollutant in vehicular emissions is

A. CO₂
B. SO₂
C. CO₂
D. O₂

View Answer

Question 186

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

View Answer

Question 187

The laying of sewers is done with

A. Magnetic compass
B. Theodolite
C. Level
D. Clinometer

View Answer

Question 188

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

View Answer

Question 189

Imhoff cone is used to measure

A. Total organic solids
B. Total solids
C. Total in organic solids
D. Settleable solids

View Answer

Question 190

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

View Answer

Question 191

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

View Answer

Question 192

Imhoff cone is used to determine

A. Settleable solids
B. Suspended solids
C. Dissolved solids
D. None of these

View Answer

Question 193

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

A. Thyroid
B. Kidneys
C. Eyes
D. Ovaries/testis

View Answer

Question 194

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

View Answer

Question 195

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

View Answer

Question 196

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

View Answer

Question 197

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

View Answer

Question 198

The water carried sewerage system removes

A. Domestic sewage
B. Industrial sewage
C. Storm sewage
D. All the above

View Answer

Question 199

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

View Answer

Question 200

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

View Answer

Question 201

Sludge banks are formed if sewage is disposed of in

A. Rivers
B. Seas
C. Lakes
D. None of these

View Answer

Question 202

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

View Answer

Question 203

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)

View Answer

Question 204

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

View Answer

Question 205

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

View Answer

Question 206

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

View Answer

Question 207

The standard B.O.D. of water is taken for

A. 1 day
B. 2 days
C. 3 days
D. 5 days

View Answer

Question 208

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

View Answer

Question 209

Water content of sewage is about

A. 90 %
B. 95 %
C. 99 %
D. 99.9 %

View Answer

Question 210

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

A. 45 %
B. 50 %
C. 55 %
D. 60 %

View Answer

Question 211

During purification process of sewage the gas given off, is

A. Carbon dioxide
B. Hydrogen
C. Ammonia
D. All the above

View Answer

Question 212

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

View Answer

Question 213

The sewer which resists sulphide corrosion, is

A. Brick sewer
B. Cast iron sewer
C. R.C. sewer
D. Lead sewer

View Answer

Question 214

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

View Answer

Question 215

The minimum diameter of a sewer is kept

A. 10 cm
B. 15 cm
C. 20 cm
D. 25 cm

View Answer

Question 216

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

View Answer

Question 217

In sewers the effect of scouring is more on

A. Top side
B. Bottom side
C. Horizontal side
D. All sides

View Answer

Question 218

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

View Answer

Question 219

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

View Answer

Question 220

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.

View Answer

Question 221

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

View Answer

Question 222

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

View Answer

Question 223

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

View Answer

Question 224

The recommended detention period for grit chambers is

A. 1 minute
B. 2 minutes
C. 3 minutes
D. 5 minutes

View Answer

Question 225

The maximum depth of sedimentation tanks, is kept

A. 3 m
B. 3.5 m
C. 4 m
D. 4.5 m

View Answer

Question 226

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

View Answer

Question 227

Kjeldahl nitrogen is a mixture of

A. Ammonia and nitrogen
B. Nitrogen and organic nitrogen
C. Organic nitrogen and ammonia
D. All the above

View Answer

Question 228

The gas which may cause explosion in sewers, is

A. carbondioxide
B. methane
C. ammonia
D. carbon monoxide.

View Answer

Question 229

The rainfall at any place may be determined by

A. Its intensity
B. Its direction
C. Its frequency
D. All the above

View Answer

Question 230

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

View Answer

Question 231

As compared to fresh river water, sea water contains oxygen

A. 10% less
B. 20% less
C. 10% more
D. 20% more

View Answer

Question 232

In sewers the gas generally found, is

A. Hydrogen sulphide (H2S)
B. Carbon dioxide (CO2)
C. Methane (CH4)
D. All the above

View Answer

Question 233

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

View Answer

Question 234

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

View Answer

Question 235

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

View Answer

Question 236

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

View Answer

Question 237

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

View Answer

Question 238

For large sewers, maximum distance between manholes may be

A. 50 m
B. 100 m
C. 200 m
D. 300 m

View Answer

Question 239

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

View Answer

Question 240

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

View Answer

Question 241

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

View Answer

Question 242

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

View Answer

Question 243

The asbestos cement pipes are generally laid

A. horizontally
B. vertically
C. at an angle of 30°
D. at an angle of 60°.

View Answer

Question 244

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)

View Answer

Question 245

The gas evolved in sewers is

A. Carbondioxide
B. Hydrogen sulphide
C. Methane
D. All of these

View Answer

Question 246

In SI units the power of sound is represented in

A. kgs
B. joules
C. neutons
D. watts.

View Answer

Question 247

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

View Answer

Question 248

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

View Answer

Question 249

The pH value of fresh sewage is usually

A. Equal to 7
B. More than 7
C. Less than 7
D. Equal to zero

View Answer

Question 250

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

View Answer

Question 251

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

View Answer

Question 252

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

View Answer

Question 253

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

A. 2 days
B. 7 days
C. 12 days
D. 14 days

View Answer

Question 254

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

View Answer

Question 255

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

View Answer

Question 256

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

View Answer

Question 257

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

View Answer

Question 258

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

View Answer

Question 259

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

View Answer

Question 260

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

View Answer

Question 261

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.

View Answer

Question 262

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

View Answer

Question 263

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

View Answer

Question 264

House connections to the laterals is generally made by

A. R.C.C.
B. P.C.C.
C. Cast iron
D. Glazed stonewares.

View Answer

Question 265

The rational formula for peak drainage discharge, was evolved by

A. Fruhling
B. Lloyd David
C. Kuichling
D. All of these

View Answer

Question 266

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

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Question 267

The formula V = (1/n) r2/3

A. Chezy’s formula
B. Bazin’s formula
C. Kutter’s formula
D. Manning’s formula

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Question 268

The minimum recommended diameter of sewers, is

A. 5 cm
B. 10 cm
C. 15 cm
D. 20 cm.

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Question 269

Are available in size Stoneware sewers

A. 10 cm
B. 15 cm
C. 20 cm
D. All the above

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Question 270

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

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Question 271

Before discharging the foul sewage into rivers, it is generally treated by

A. Screening
B. Sedimentation
C. Oxidation
D. All the above

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Question 272

The gas which may cause explosion in sewers, is

A. Carbondioxide
B. Methane
C. Ammonia
D. Carbon monoxide

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Question 273

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

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Question 274

The gradient of sewers depends upon

A. Velocity of flow
B. Diameter of the sewer
C. Discharge
D. All the above

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Question 275

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

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Question 276

Removal of oil and grease from sewage, is known

A. screening
B. skimming
C. filtration
D. none of these.

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Question 277

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.

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Question 278

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

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Question 279

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

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Question 280

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

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Question 281

In a sludge tank, the gas mainly produced, is

A. Oxygen
B. Nitrogen
C. Hydrogen
D. Carbon dioxide

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Question 282

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

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Question 283

An inverted siphon is designed generally for

A. One pipe
B. Two pipes
C. Three pipes
D. Four pipes

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Question 284

In sewers the effect of scouring is more on

A. top side
B. bottom side
C. horizontal side
D. all sides.

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Question 285

Design period of 40 to 50 years is adopted for

A. Branch sewers
B. Main sewers
C. Trunk sewers
D. All the above

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Question 286

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.

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Question 287

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

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Question 288

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

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Question 289

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

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Question 290

Pathogens (or pathogenic bacterias) in water may cause

A. Typhoid
B. Cholera
C. Dysentery
D. All the above

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Question 291

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

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Question 292

The porosity of sediments in sewer pipes, is usually taken as

A. 0.01
B. 0.011
C. 0.012
D. 0.013

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Question 293

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

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Question 294

The sewerage system originates from

A. House sewers
B. Lateral sewers
C. Branch sewers
D. Main sewers

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Question 295

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

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Question 296

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

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Question 297

Primary treatment of sewage consists of removal of

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

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Question 298

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

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Question 299

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

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Question 300

A rain sanitary sewer is constructed to carry

A. sanitary sewage
B. storm sewage
C. surface water
D. ground water

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Question 301

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

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Question 302

In a trickling filter

A. Filtration process is used
B. Biological action is used
C. Neither A nor B
D. Both A and B

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Question 303

House connections to the laterals is generally made by

A. R.C.C.
B. P.C.C.
C. Cast iron
D. Glazed stonewares

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Question 304

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

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Question 305

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

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Question 306

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

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Question 307

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

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Question 308

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

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Question 309

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

A. Parabolic
B. Circular
C. Rectangular
D. New egged

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Question 310

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

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Question 311

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

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Question 312

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

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Question 313

The following is the physical characteristic of sewage

A. Turbidity
B. Colour
C. Odour
D. All the above

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Question 314

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

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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.

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Question 316

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

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Question 317

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.

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Question 318

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

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Question 319

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

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Question 320

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

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Question 321

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

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Question 322

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

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Question 323

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

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Question 324

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

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Question 325

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

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Question 326

The small sewers are cleaned by

A. Flushing
B. Cane rodding
C. Wooden pills
D. None of these

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Question 327

The sewerage system consists of

A. House sewer
B. Lateral sewer
C. Branch sewer
D. All of these

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Question 328

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

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Question 329

The minimum recommended diameter of sewers, is

A. 5 cm
B. 10 cm
C. 15 cm
D. 20 cm

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Question 330

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

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Question 331

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

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Question 332

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

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Question 333

For design of sewers, percentage of sewage discharge is assumed

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

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Question 334

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

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Question 335

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

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Question 336

Disposal to sewage in large cities, is done in

A. irrigation
B. dilution
C. oxidation
D. putrifaction.

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Question 337

In SI units the power of sound is represented in

A. Kgs
B. Joules
C. Newtons
D. Watts

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Question 338

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.

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Question 339

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

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Question 340

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

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Question 341

The underground sewers are more subjected to

A. Tensile force
B. Compressive force
C. Bending force
D. Shearing force

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Question 342

Flocculated particles do not change their

A. size
B. shape
C. weight
D. none of these.

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Question 343

Which one of the following resists hydrogen sulphide corrosion?

A. R.C.C.
B. Glazed stone wares
C. Asbestos cement
D. Glazed ware

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