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.

 Answer Option B

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%.

 Answer Option B

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.

 Answer Option D

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

A.

B.

C.

D.

 Answer Option C

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.

 Answer Option E

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.

 Answer Option A

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.

 Answer Option A

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

A. lung cancer

B. skin cancer

C. bronchitis

D. heart disorder.

 Answer Option B

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.

 Answer Option A

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.

 Answer Option A

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.

 Answer Option D

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

A. thyroid

B. kidneys

C. eyes

D. ovaries/testis.

 Answer Option D

13. The water carried sewerage system removes

A. domestic sewage

B. industrial sewage

C. storm sewage

D. all the above.

 Answer Option D

14. Stoneware sewers are available in size

A. 10 cm

B. 15 cm

C. 20 cm

D. 25 cm

E. all the above.

 Answer Option E

15. The sludge does not contain waste water from

A. bath rooms

B. wash basins

C. kitchen sinks

D. toilets.

 Answer Option D

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.

 Answer Option C

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.

 Answer Option C

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

A. rivers

B. seas

C. lakes

D. none of these.

 Answer Option B

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

A. branch sewers

B. main sewers

C. trunk sewers

D. all the above.

 Answer Option D

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

A. Imhoff Cone

B. turbidimeter

C. potentiometer

D. none of these.

 Answer Option C

21. Lead caulked joints are used for laying

A. stone ware pipes

B. earthern ware pipes

C. C.I. pipes

D. G.I. pipes.

 Answer Option B

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.

 Answer Option A

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

 Answer Option A

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.

 Answer Option D

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.

 Answer Option A

26. The rainfall at any place may be determined by

A. its intensity

B. its direction

C. its frequency

D. all the above.

 Answer Option D

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%.

 Answer Option C

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

A. Carbondioxide

B. Oxygen

C. Nitrogen

D. Sulphurdioxide.

 Answer Option D

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.

 Answer Option D

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.

 Answer Option B

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.

 Answer Option C

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

A. 1

B. 2 to 3

C. 3 to 5

D. 5 to 10

 Answer Option D

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.

 Answer Option E

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

 Answer Option D

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.

 Answer Option C

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.

 Answer Option C

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.

 Answer Option B

38. The average temperature of sewage in India, is

A. 10°C

B. 15°C

C. 20°C

D. 25°C

E. 30°C.

 Answer Option C

39. The most widely used pump for lifting sewage is

A. centrifugal pump

B. reciprocating pump

C. pneumatic ejector

D. air pressure pump.

 Answer Option A

40. The sewer which resists sulphide corrosion, is

A. Brick sewer

B. Cast iron sewer

C. R.C.C. sewer

D. Lead sewer

E. None of these.

 Answer Option D

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.

 Answer Option D

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

A. acid fermentation

B. acid regression

C. alkaline fermentation

D. none of these.

 Answer Option A

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.

 Answer Option B

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.

 Answer Option A

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).

 Answer Option C

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.

 Answer Option D

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.

 Answer Option C

48. Water content of sewage is about

A. 90%

B. 95%

C. 99.9%

D. 9.9%.

 Answer Option C

49. Imhoff cone is used to measure

A. total organic solids

B. total solids

C. total in organic solids

D. settleable solids.

 Answer Option D

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.

 Answer Option C