Civil Engineering - Waste Water Engineering MCQs Part 2

1. The most dangerous pollutant in vehicular emissions is

A.
CO

B.
SO2

C.
CO2

D.
O3.

 Answer Option A

2. 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.
200 mg/l

E.
250 mg/l.

 Answer Option E

3. 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 Option D

4. 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.

 Answer Option C

5. 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 Option C

6. 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.

 Answer Option A

7. 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.

 Answer Option C

8. The gradient of sewers depends upon

A. velocity of flow

B. diameter of the sewer

C. discharge

D. all the above.

 Answer Option D

9. 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

E. 3 hours.

 Answer Option D

10. 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.

 Answer Option C

11. 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.

 Answer Option D

12. 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. surface loading is limited to 30, 000 litres/m of plan area per day

E. All the above.

 Answer Option E

13. If the depth of partial flow in a sewer of diameter 2 m, is 50 cm, its wetted perimeter is

A. π

B.

C.

D.

E.

 Answer Option D

14. 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.

 Answer Option B

15. 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

 Answer Option D

16. 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.

 Answer Option D

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

A. liquid waste

B. sullage

C. sewage

D. none of these.

 Answer Option C

18. The presence of free ammonia in sewage, is detected by

A. boiling

B. adding pottassium permanganate

C. adding sulphuric acid

D. phenol-di-sulphuric acid.

 Answer Option A

19. 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 Option B

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

A. 1 day

B. 2 days

C. 3 days

D. 5 days

E. 10 days.

 Answer Option D

21. 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

E. 1.0 m/sec.

 Answer Option D

22. Pick up the correct statement from the following :

A. Turbidity is more in strong sewage

B. The black colour indicates septic sewage

C. The fresh sewage is practically odourless

D. The sewage omits offensive odours after four hours

E. All the above.

 Answer Option E

23. In sewers the gas generally found, is

A. Hydrogen sulphide (H2S)

B. Carbon dioxide (CO2)

C. Methane (CH4)

D. Petrol vapours

E. All the above.

 Answer Option E

24. 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.

 Answer Option D

25. 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

E. 1.2 to 1.50 m.

 Answer Option C

26. For a circular sewer of diameter D running partially full with central angle α,

A.

B.

C.

D.

E. all the above.

 Answer Option E

27. 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

E. 2500 litres/km/cm.

 Answer Option D

28. 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 Option A

29. 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 the maximum run off is

A. 0.10 cumec

B. 0.12 cumec

C. 0.15 cumec

D. 0.20 cumec.

 Answer Option C

30. 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.

 Answer Option A

31. Fresh sewage may become stale in

A. one hour

B. two to three hours

C. three to four hours

D. six hours.

E. ten hours.

 Answer Option C

32. The small sewers are cleaned by

A. flushing

B. cane rodding

C. wooden pills

D. none of these.

 Answer Option A

33. 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.

 Answer Option D

34. 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.

 Answer Option D

35. 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

E. None of these.

 Answer Option A

36. 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.

 Answer Option A

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

A. nitrites

B. nitrates

C. free ammonia

D. aluminoid nitrogen

E. none of these.

 Answer Option B

38. 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 Option C

39. 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.

 Answer Option D

40. 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.

 Answer Option D

41. 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. the inlet is kept 30 cm below the sewage line and outlet is kept at a level 40% depth of the sewage

E. all the above.

 Answer Option E

42. 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.

 Answer Option A

43. The algae dies out in the zone of

A. degradation

B. active decomposition

C. recovery

D. cleaner water.

 Answer Option A

44. The recommended detention period for grit chambers is

A. 1 minute

B. 2 minutes

C. 3 minutes

D. 5 minutes.

 Answer Option A

45. 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 called incineration

D. The process of burning the screenings, is known as compositing

E. All the above.

 Answer Option E

46. 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

 Answer Option A

47. Pick up the correct statement from the following :

A. The maximum rate of storm run off 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 run off, is called the time of concentration

D. The time required by water to reach the outlet of a catchment from the most remote point, is called time of concentration

E. All the above.

 Answer Option E

48. 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

E. semi-elliptical shaped.

 Answer Option C

49. 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. Septic tanks are generally classified as tanks which work on the principle of anaerobic decomposition

E. None of these.

 Answer Option E

50. 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.

 Answer Option D