### Civil Engineering - Waste Water Engineering MCQs Part 3

1. The pH value of fresh sewage is usually

A.
equal to 7
B.
more than 7
C.
less than 7
D.
equal to zero.

2. The moisture content of a 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%.

3. 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.

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

A.
B.
C.
D.

5. The factor responsible for purification of sewage in river is

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

6. If the peak discharge of a storm water drain (S.W. Drain) is e.xpected to exceed 150 cumecs, the free board to be provided, is

A. 100 cm
B. 90 cm
C. 80 cm
D. 50 cm.

7. 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.

8. Depletion of ozone layer in the outer atmosphere may cause

A. lung cancer
B. skin cancer
C. bronchitis
D. heart disorder.

9. 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.

10. 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.

11. Ventilating shafts are provided to a sewer line at every

A. 100 m
B. 150 m
C. 200 m
D. 300 m
E. 500 m.

12. Which one of the following part of human body withstands minimum radiation

A. thyroid
B. kidneys
C. eyes
D. ovaries/testis.

13. The water carried sewerage system removes

A. domestic sewage
B. industrial sewage
C. storm sewage
D. all the above.

14. Stoneware sewers are available in size

A. 10 cm
B. 15 cm
C. 20 cm
D. 25 cm
E. all the above.

15. The sludge does not contain waste water from

A. bath rooms
B. wash basins
C. kitchen sinks
D. toilets.

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

A.
B.
C.
D. πD.

17. 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.

18. Sluge banks are formed if sewage is disposed of in

A. rivers
B. seas
C. lakes
D. none of these.

19. Design period of 40 to 50 years is adopted for

A. branch sewers
B. main sewers
C. trunk sewers
D. all the above.

20. The pH value of sewage is determined with the help of

A. Imhoff Cone
B. turbidimeter
C. potentiometer
D. none of these.

21. Lead caulked joints are used for laying

A. stone ware pipes
B. earthern ware pipes
C. C.I. pipes
D. G.I. pipes.

22. 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
E. None of these.

23. 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. 2.0
C. 2.5
D. 3.0
E. 3.5

24. 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.

25. Primary treatment of sewage consists of removal of

A. large suspended organic solids
B. oil and grease
C. sand and girt
D. floating materials
E. none of these.

26. The rainfall at any place may be determined by

A. its intensity
B. its direction
C. its frequency
D. all the above.

27. 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%
E. 95%.

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

A. Carbondioxide
B. Oxygen
C. Nitrogen
D. Sulphurdioxide.

29. 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.

30. 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.

31. 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.

32. The design period in years for pumping plants, is

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

33. 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. hydraulic characteristics of sewer
E. all the above.

34. Afive 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

35. 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
E. 0.0558 cumec.

36. For the open drain (N = 0.025) shown in the below figure, the discharge is

A. 26.88 cumecs
B. 27.88 cumecs
C. 28.88 cumecs
D. 29.88 cumecs.

37. 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.

38. The average temperature of sewage in India, is

A. 10°C
B. 15°C
C. 20°C
D. 25°C
E. 30°C.

39. The most widely used pump for lifting sewage is

A. centrifugal pump
B. reciprocating pump
C. pneumatic ejector
D. air pressure pump.

40. The sewer which resists sulphide corrosion, is

A. Brick sewer
B. Cast iron sewer
C. R.C.C. sewer
E. None of these.

41. For large sewers, maximum distance between manholes may be

A. 50 m
B. 100 m
C. 200 m
D. 300 m
E. 400 m.

42. The first stage of neutral process of sludge digestion, is

A. acid fermentation
B. acid regression
C. alkaline fermentation
D. none of these.

43. 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.

44. Dried sewage after treatment is used as

A. fertilizer
B. building material
C. chemical for lowering B.O.D.
D. base material for paints.

45. 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).

46. 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.

47. 5 days-biochemical oxygen demand (BOD5) is taken at a temperature of

A. 0°C
B. 15°C
C. 20°C
D. 25°C.

48. Water content of sewage is about

A. 90%
B. 95%
C. 99.9%
D. 9.9%.

49. Imhoff cone is used to measure

A. total organic solids
B. total solids
C. total in organic solids
D. settleable solids.

50. 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.