Waste Water Engineering MCQ Questions and Answers in Civil Engineering

Question. 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

Question. 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

Question. 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

Answer : D

Question. The porosity of sediments in sewer pipes, is usually taken as
(a) 0.010
(b) 0.011
(c) 0.012
(d) 0.013

Answer : D

Question. 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

Answer : C

Question. 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

Question. 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

Answer : D

Question. Discrete or granular particles change their
(a) Size
(b) Shape
(c) Weight
(d) None of these

Answer : D

Question. 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

Answer : D

Question. 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

Answer : C

Question. 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

Answer : A

Question. 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

Answer : C

Question. 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

Answer : C

Question. 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

Question. 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

Question. 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

Question. R.M.O. expenses include
(a) Running expenses
(b) Maintenance expenses
(c) Operation expenses
(d) All the above

Answer : D

Question. 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

Question. 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

Question. 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

Question. 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

Question. 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

Answer : D

Question. 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

Answer : D

Question. 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

Question. 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

Question. 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

Answer : B

Question. The suitable cross-section of sewers to carry combined flow, is
(a) Circular
(b) Egg shaped
(c) Rectangular
(d) Horse shoe shaped

Answer : B

Question. Are available in size Stoneware sewers
(a) 10 cm
(b) 15 cm
(c) 20 cm
(d) All the above

Answer : D

Question. 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

Answer : D

Question. 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

Question. 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

Answer : D

Question. 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

Answer : C

Question. 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

Question. The rainfall at any place may be determined by
(a) Its intensity
(b) Its direction
(c) Its frequency
(d) All the above

Answer : D

Question. 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

Answer : C

Question. Removal of oil and grease from sewage, is known
(a) Screening
(b) Skimming
(c) Filtration
(d) None of these

Answer : B

Question. 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

Question. Which one of the following gases is most significant as air pollutant?
(a) Carbondioxide
(b) Oxygen
(c) Nitrogen
(d) Sulphur-dioxide

Answer : D

Question. 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

Answer : D

Question. 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

Answer : C

Question. 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

Answer : A

Question. The recommended detention period for grit chambers is
(a) 1 minute
(b) 2 minutes
(c) 3 minutes
(d) 5 minutes

Answer : A

Question. 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

Answer : D

Question. In a trickling filter
(a) Filtration process is used
(b) Biological action is used
(c) Neither A nor B
(d) Both A and B

Answer : B

Question. 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

Answer : C

Question. The standard b.O.d. of water is taken for
(a) 1 day
(b) 2 days
(c) 3 days
(d) 5 days

Answer : D

Question. 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

Answer : C

Question. 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

Answer : A

Question. 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

Answer : C

Question. 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

Answer : D

Question. Oxidation process results in the formation of
(a) Carbon dioxide
(b) Nitrates
(c) Sulphates
(d) All the above

Answer : D

Question.  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

Answer : B

Question. 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

Answer : B

Question. The sludge does not contain waste water from
(a) Bath rooms
(b) Wash basins
(c) Kitchen sinks
(d) Toilets

Answer : D

Question. For laying a sewer line in a trench of 2 m width, an offset line is marked on the ground paallel to the given centre line at a distance of
(a) 100 cm
(b) 120 cm
(c) 140 cm
(d) 160 cm

Answer : D

Question. Flocculated particles do not change their
(a) Size
(b) Shape
(c) Weight
(d) None of these

Answer : D

Question. The minimum diameter of sewer to be adopted is
(a) 10 cm
(b) 12.5 cm
(c) 15 cm
(d) 25 cm

Answer : C

Question. 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

Answer : D

Question. 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

Question. 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

Question. 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

Answer : D

Question. 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

Answer : D

Question. 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

Answer : C

Question. A manhole is generally provided at each
(a) Bend
(b) Junction
(c) Change of gradient
(d) All the above

Answer : D

Question. 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

Answer : A

Question. 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

Question. In R.C sewer pipes, the percentage longitudinal reinforcement to the cross-sectional area of concrete is kept
(a) 10.0
(b) 5.0
(c) 2.0
(d) 0.25

Answer : D

Question. Clogging of sewers, is caused due to
(a) Silting
(b) Low discharge
(c) Greasy and oily matters
(d) All the above

Answer : D

Question. A nuisance is experienced in diluting water if dilution factor is less than
(a) 100
(b) 60
(c) 40
(d) 20

Answer : D

Question. The sewage treatment in septic tanks is due to
(a) Anaerobic decomposition
(b) Aerobic decomposition
(c) Parasitic decomposition
(d) None of these

Answer : A