### Civil Engineering - Waste Water Engineering MCQs Part 1

1. The minimum recommended diameter of sewers, is

A.
5 cm
B.
10 cm
C.
15 cm
D.
20 cm.

2. 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.

3. The rate of accumulation of sludge in septic tanks is recommended as

A.
30 litres/person/year
B.
25 litres/person/year
C.
30 litres/person/month
D.
25 litres/person/month.

4. 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.

5. If D is the diameter of upper circular portion, the overall depth of a standard egg shaped section, is

A.
D
B.
1.25 D
C.
1.5 D
D.
1.75 D
E.
2 D.

6. If the diameter of sewer is 225 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.

7. Pick up the correct statement from the following :

A. pH value indicates acidity and alkalinity of sewage
B. In acidic sewage, the pH value is less than 7
C. In alkaline sewage, the pH value is more than 7
D. Fresh sewage is generally alkaline
E. All the above.

8. The non-clog pump which permits solid matter to pass out with the liquid sewage, is

A. centrifugal pump
B. reciprocating pump
C. pneumatic ejector
D. none of these.

9. Assertion (A) : Discharging the effluents from the oxidation ponds just up stream of lakes or reservoirs is undesirable. Reason (R) : The discharged algae get settled in the reservoirs and cause anaerobic decomposition and other water qualities.

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.

10. The width of a rectangular sewer is twice its depth while discharging 1.5 m/sec. The width of the sewer is

A. 0.68 m
B. 0.88 m
C. 1.36 m
D. 1.76 m.

11. Pick up the correct statement from the following :

A. In treated sewage, 4 PPm of D.O. is essential
B. Only very fresh sewage contains some dissolved oxygen
C. The solubility of oxygen in sewage is 95% that is in distilled water
D. All the above.

12. In olden days the type of section adopted in trunk and out fall sewers was

A. parabolic shaped
B. horse shoe shaped
C. egg shaped
D. circular shaped.

13. For the survival of fish in a river stream, the minimum dissolved oxygen is prescribed

A. 3 PPm
B. 4 PPm
C. 5 PPm
D. 10 ppm.

14. In a fully mechanised composting plant, involves

A. mechanized receipt
B. mechanized segregation
C. mechanized pulverising of refuse
D. all of these.

15. Self-cleansing velocity is

A. velocity at dry weather flow
B. velocity of water at flushing
C. velocity at which no accumulation remains in the drains
D. velocity of water in a pressure filter.

16. If the over land flow from the critical point to the drain is 8 km and the difference in level is 12.4 m, the inlet time is

A. 2 hours
B. 3 hours
C. 4 hours
D. 5 hours.

17. An inverted siphon is designed generally for

A. one pipe
B. two pipes
C. three pipes
D. four pipes.

18. 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

19. When drainage to sewage ratio is 20, the peak dry weather flow is

A. 20% of the design discharge
B. slightly less than 5% of the design discharge
C. slightly more than 5% of the design discharge
D. none of these.

20. For treating the sewage of a large city, you will recommend

A. a sedimentation tank and an activated sludge treatment plant
B. a plant consisting of Imhoff tanks with low rate trickling filters
C. sedimentation tanks with high rate trickling filters
D. none of these.

21. The detention time of a circular tank of diameter d and water depth H, for receiving the sewage Q per hour, is

A.
B.
C.
D.

22. The dimensions of a rectangular settling tank are : length 24 m, width 6 m and depth 3 m. If 2 hour detention period for tanks is recommended, the rate of flow of sewage per hour, is

A. 204 cu m
B. 208 cu m
C. 212 cu m
D. 216 cu m
E. 220 cu m.

23. The screens are fixed

A. perpendicular to the direction of flow
B. parallel to the direction of flow
C. at an angle 30° to 60° to the direction of flow
D. none of these.

24. In primary sedimentation, the 0.2 mm inorganic solids get separated if specific gravity is

A. 2.25
B. 2.50
C. 2.55
D. 2.65
E. 2.75

25. Pick up the in-correct statement from the following :

A. Manholes are provided in sewer pipes at suitable intervals
B. Catch basins are generally provided in sewers for carrying drainage discharge
C. Inlets are generally provided in all sewers
D. None of these.

26. Clogging of sewers, is caused due to

A. silting
B. low discharge
C. greasy and oily matters
D. domestic wastes thrown in manholes
E. all the above.

27. 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
E. 0.50 m/sec.

28. The coagulant widely used for sewage treatment, is

A. alum
B. ferric chloride
C. ferric sulphate
D. chlorinated copperas.

29. House connections to the laterals is generally made by

A. R.C.C.
B. P.C.C.
C. Cast iron
D. Glazed stonewares.

30. The ratio of maximum sewage flow to average sewage flow for mains up to 1 m in diameter, is

A. 1.5
B. 2.0
C. 3.0
D. 4.0

31. Dilution method of disposing off 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
E. none of these.

32. For house drainage minimum gradient is

A. 1 in 60
B. 1 in 80
C. 1 in 10
D. 1 in 400

33. If the side of a square sewer is 1000 mm, the diameter of a hydraulically equivalent circular section, is

A. 1045 mm
B. 1065 mm
C. 1075 mm
D. 1095 mm.

34. The ratio of minimum hourly flow to the average flow of sewage is

A. 1/4
B. 1/3
C. 1/2
D. 3/4

35. Bio-chemical oxygen demand (BOD) for the first 20 days in generally referred to

A. initial demand
B. first stage demand
C. carbonaceous demand
D. all of these.

36. Flocculated particles do not change their

A. size
B. shape
C. weight
D. none of these.

37. 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.

38. Disposal to sewage in large cities, is done in

A. irrigation
B. dilution
C. oxidation
D. putrifaction.

39. For the COD test of sewage, organic matter is oxidised by K2Cr207 in the presence of

A. H2SO4
B. HNO3
C. HCl
D. none of these.

40. 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

41. The asbestos cement pipes are generally laid

A. horizontally
B. vertically
C. at an angle of 30°
D. at an angle of 60°.

42. Chlorination of water is done for the removal of

A. bacterias
B. suspended solids
C. sediments
D. hardness.

43. For evaporation and measurement of settlable solids, the apparatus used, is

A. a jar
B. a breaker
C. a test tube
D. an Imhoff cone.

44. In SI units the power of sound is represented in

A. kgs
B. joules
C. neutons
D. watts.

45. A rain sanitary sewer is constructed to carry

A. sanitary sewage
B. storm sewage
C. surface water
D. ground water
E. all the above.

46. The sewage is pumped up

A. from low lying areas
B. from flat areas
C. from basements
D. across a high ridge
E. all the above.

47. Removal of oil and grease from sewage, is known

A. screening
B. skimming
C. filtration
D. none of these.

48. The gas which may cause explosion in sewers, is

A. carbondioxide
B. methane
C. ammonia
D. carbon monoxide.

49. In sewers the effect of scouring is more on

A. top side
B. bottom side
C. horizontal side
D. all sides.