Environment Engineering MCQ
51 The pH value of sewage is determined with the help of
(A) Imhoff Cone
(B) Turbid meter
(C) Potentiometer
(D) None of these
Ans. C
52 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
Ans. B
53 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
Ans. D
54 In a trickling filter
(A) Filtration process is used
(B) Biological action is used
(C) Neither (a) nor (b)
(D) Both (a) and (b)
Ans. B
55 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
Ans. C
56 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
Ans. A
57 Dried sewage after treatment is used as
(A) Fertilizer
(B) Building material
(C) Chemical for lowering B.O.D.
(D) Base material for paints
Ans. A
58 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
Ans. B
59 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
Ans. B
60 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
Ans. C
61 5 days-biochemical oxygen demand (BOD5) is taken at a temperature of
(A) 0°C
(B) 15°C
(C) 20°C
(D) 25°C
Ans. C
62 A well oxidized sewage contains nitrogen mainly as
(A) Nitrates
(B) Nitrites
(C) Free ammonia
(D) None of these
Ans. A
63 In a sludge tank, the gas mainly produced, is
(A) Oxygen
(B) Nitrogen
(C) Hydrogen
(D) Carbon dioxide
Ans. D
64 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
Ans. D
65 In normal conditions, the period for sludge digestion, is
(A) 10 days
(B) 20 days
(C) 30 days
(D) 60 days
Ans. C
66 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
Ans. D
67 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%
Ans. C
68 For design of sewers, percentage of sewage discharge is assumed
(A) 65 to 70
(B) 70 to 75%
(C) 75 to 80%
(D) 85%
Ans. C
69 The grit chambers of sewage treatment plants, are generally cleaned after
(A) 2 days
(B) 7 days
(C) 12 days
(D) 14 days
Ans. D
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)
Ans. C
71 The average temperature of sewage in India, is
(A) 10°C (B) (C) (D)
(B) 15°C
(C) 20°C
(D) 25°C
Ans. C
72 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
Ans. C
73 A well oxidized sewage contains nitrogen mainly as
(A) Nitrates
(B) Nitrites
(C) Free ammonia
(D) None of these
Ans. A
74 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 %
Ans. B
75 In a sludge tank, the gas mainly produced, is
(A) Oxygen
(B) Nitrogen
(C) Hydrogen
(D) Carbon dioxide
Ans. D
76 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
Ans. D
80 In normal conditions, the period for sludge digestion, is
(A) 10 days
(B) 20 days
(C) 30 days
(D) 60 days
Ans. C
81 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
Ans. D
82 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%
Ans. C
83 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%
Ans. C
84 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
Ans. D
85 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
Ans. B
86 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
Ans. C
87 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]
Ans. B
88 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
Ans. D
89 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
Ans. D
90 The intensity of rain is expressed in
(A) cm/minute (B) (C) (D)
(B) cm/hour
(C) cm/day
(D) None of these
Ans. B
91 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
Ans. A
92 Which one of the following part of human body withstands minimum radiation?
(A) Thyroid
(B) Kidneys
(C) Eyes
(D) Ovaries/testis
Ans. D
93 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
Ans. D
94 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
Ans. B
95 Primary treatment of sewage consists of removal of
(A) Large suspended organic solids
(B) Oil and grease
(C) Sand and girt
(D) Floating materials
Ans. A
96 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
Ans. A
97 The most widely used pump for lifting sewage is
(A) Centrifugal pump
(B) Reciprocating pump
(C) Pneumatic ejector
(D) Air pressure pump
Ans. A
98 Setting out the alignments of sewers may start from
(A) City
(B) Out-fall
(C) Tail end
(D) Any point
Ans. C
99 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
Ans. A
100 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
Ans. B
