Civil Engineering - Waste Water Engineering MCQs Part 5

1. Sewer pipes need be checked for

A.
minimum flow

B.
maximum flow

C.
both (a) and (b)

D.
none of these.

 Answer Option C

2. 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

E.
none of these.

 Answer Option B

3. The ratio of design discharge to the surface area of a sedimentation tank is called

A.
surface loading

B.
overflow rate

C.
overflow velocity

D.
all of these.

 Answer Option D

4. The value of Chezy's constant is used in

A.
Chezy's formula

B.
Bazin's formula

C.
Kutter's

D.
Manning's formula.

 Answer Option C

5. 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.

 Answer Option B

6. The minimum diameter of a sewer is kept

A. 10 cm

B. 15 cm

C. 20 cm

D. 25 cm

E. 30 cm.

 Answer Option B

7. The minimum diameter of sewer to be adopted is

A. 10 cm

B. 12.5 cm

C. 15 cm

D. 25 cm.

 Answer Option C

8. To test chemical oxygen demand (C.O.D.) of sewage, organic matter is oxidised by pottassium dichromate in the presence of

A. Hydrochloric acid

B. Sulphuric acid

C. Nitric acid

D. Citric acid.

 Answer Option B

9. 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 Option D

10. In a sedimentation tank (length L, width B, depth D) the settling velocity of a particle for a discharge Q, is

A.

B.

C.

D.

 Answer Option D

11. D is the diameter of a circular sewer and α is the side of a square section sewer. If both are hydraulically equivalent, the relationship which holds good, is

A. πD8/3 = 4 b8/3

B. πD3/8 = 4 b3/8

C. πD2/3 = 4 b2/3

D. πD3/2 = 4 b3/2

E. none of these.

 Answer Option A

12. For detecting the nitrites in the sewage, the matching colour may be developed by adding

A. Pottassium permanganate

B. Sulphuric acid and napthamine

C. Phenol-di-sulphuric acid pottassium hydroxide

D. None of these.

 Answer Option B

13. The suitable cross-section of sewers to carry combined flow, is

A. circular

B. egg shaped

C. rectangular

D. horse shoe shaped.

 Answer Option B

14. Hazin's formula is used for the settlement velocity of the particles of diameter

A. less than 0.01 mm

B. less than 0.05 mm

C. less than 0.1 mm

D. greater than 0.1 mm.

 Answer Option D

15. If the diameter of a sewer is 100 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 A

16. Stone ware pipes are

A. highly resistant to sulphide corrosion

B. highly impervious

C. hydraulically efficient because of their smooth interior surface

D. specially suited to pressure pipes

E. none of these.

 Answer Option D

17. Skimming tanks are

A. used to remove the grease and oil

B. those from which sludge is skimmed out

C. tanks provided with self-cleansing screens

D. improved version of grit chambers.

 Answer Option A

18. In a sludge digestion tank if the moisture content of sludge V1 litres is reduced from p1 % to p2 % the volume V2 is

A.

B.

C.

D.

 Answer Option C

19. Assertion (A) : The determination of pH value of sewerage is important. Reason (R) : The efficiency of certain treatment methods depends upon the availability of pH value.

A. Both A and R are true and R is the correct explanation of A

B. Both A and R are true but R is not a correct explanation of A

C. A is true but R is false

D. A is false but R is true.

 Answer Option A

20. With self cleansing velocity in sewers

A. silting occurs at bottom

B. scouring occurs at bottom

C. both silting and scouring occur at bottom

D. neither silting nor scouring occurs at bottom.

 Answer Option D

21. Aerobic activity is maximum

A. in freshly produced sewage

B. at sewer pipes

C. in sewer treatment plants

D. none of these.

 Answer Option A

22. In sewers designed with self cleansing velocity,

A. the bottom is silted

B. the bottom is scoured

C. both silting and scouring occur at the bottom

D. neither silting nor scouring occurs at the bottom.

 Answer Option D

23. Which one of the following resists hydrogen sulphide corrosion

A. R.C.C.

B. Glazed stone wares

C. Asbestos cement

D. Glazed ware.

 Answer Option D

24. The sewerage system consists of

A. house sewer

B. lateral sewer

C. branch sewer

D. main sewer

E. all of these.

 Answer Option E

25. Hume steel pipes are

A. steel pipes

B. R.C.C. pipes

C. steel shell coated from inside with cement mortar

D. steel shell coated from outside with cement mortar

E. both (c) and (d).

 Answer Option E

26. 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 Option D

27. Boussinesq's equation for ascertaining unit pressure at a depth H on sewers due to traffic loads, is

A.

B.

C.

D.

E. none of these.

 Answer Option A

28. The laying of sewers is done with

A. magnetic compass

B. theodolite

C. level

D. clinometer

E. plane table.

 Answer Option C

29. The rational formula for peak drainage discharge, was evolved by

A. Fruhling

B. Lloyd David

C. Kuichling

D. All of these.

 Answer Option D

30. The sewage treatment in septic tanks is due to

A. anaerobic decomposition

B. aerobic decomposition

C. parasitic decomposition

D. none of these.

 Answer Option A

31. In 1000 kg of sewage, the total solids approximate

A. 0.5 to 1.0 kg

B. 1 kg to 2.0 kg

C. 5 kg to 7.5 kg

D. 7.5 kg to 10 kg.

 Answer Option A

32. Pathogens (or pathogentic bacterias) in water may cause

A. typhoid

B. cholera

C. dysentery

D. infectious hepatitis

E. all the above.

 Answer Option E

33. Sewer manholes are generally provided at

A. the change of gradient

B. the change of direction

C. the junctions of sewers

D. all of these.

 Answer Option D

34. The sewers

A. must be of adequate size to avoid over flow

B. must flow under gravity to full

C. must be laid at least 2 to 3 m deep to collect /water from the basements

D. all the above.

 Answer Option D

35. Before discharging the foul sewage into rivers, it is generally treated by

A. screening

B. sedimentation

C. oxidation

D. sludge digestion and disinfection

E. all the above.

 Answer Option E

36. The settlement of a particle in sedimentation tank, is affected by

A. velocity of flow

B. viscosity of water

C. size and shape of solid

D. specific gravity of solid

E. all the above.

 Answer Option E

37. If the length of overland flow from the critical point to the mouth of drain is 13.58 km and difference in level between the critical point and drain mouth is 10 m, the inlet time is

A. 2 hours

B. 4 hours

C. 6 hours

D. 8 hours.

 Answer Option D

38. Oxidation process results in the formation of

A. carbon dioxide

B. nitrates

C. sulphates

D. all the above.

 Answer Option D

39. 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

E. none of these.

 Answer Option D

40. As compared to fresh river water, sea water contains oxygen

A. 10% less

B. 20% less

C. 10% more

D. 20% more.

 Answer Option B

41. The settlement velocity of a solid (diameter 0.5 mm, specific gravity 1.75) in water having temperature 10°C, is

A. 213.5 cm/sec

B. 313.5 cm/sec

C. 413.5 cm/sec

D. 500 cm/sec.

 Answer Option B

42. If γw is the unit weight of water, r the hydraulic mean depth of the sewer and S the bed slope of the sewer, then the tractive force exerted by flowing water, is

A. γw . r . S

B. γw r1/2 . S

C. γw r S

D. γw r2/3 S

 Answer Option A

43. In detritus tanks,

A. flow velocity is kept 0.09 m/sec

B. detention period is kept 3 to 4 minutes

C. organic and inorganic materials are separated

D. all the above.

 Answer Option D

44. 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 m

D. 6.5 m

E. 7 m.

 Answer Option E

45. 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.

 Answer Option C

46.  rd or th extra space is left in sewer pipes at maximum discharge for

A. low estimates of the average and maximum flows

B. large scale infiltration of storm water

C. unexpected increase in population

D. all the above.

 Answer Option D

47. If n is the rugosity coefficient, r is the hydraulic depth, s is the bed slope of sewer, the velocity of flow in m/sec may be obtained by the formula evolved by

A. Chezy

B. Manning

C. Bazin

D. Kutter.

 Answer Option B

48. Pick up the correct statement from the following :

A. anaerobic bacteria flourish in the absence of oxygen

B. aerobic bacteria flourish in the presence of oxygen

C. facultative bacteria flourish with or without oxygen

D. all the above.

 Answer Option D

49. Antisyphonage pipe is fitted

A. at the end of septic tanks

B. on manholes

C. with a W.C. trap

D. at the beginning of sewer line.

 Answer Option C

50. For drains up to 15 cumecs, the depth d and width B are related by

A. d = 0.2 B

B. d = 0.5 B

C. B = 0.2 d

D. B = 0.5 d.

 Answer Option B