Waste Water Civil Engineering Questions and Answers - Set 02 - ObjectiveBooks

Waste Water Civil Engineering Questions and Answers - Set 02

Practice Test: Question Set - 02

1. The gas which may cause explosion in sewers, is
    (A) Carbondioxide
    (B) Methane
    (C) Ammonia
    (D) Carbon monoxide

2. 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

3. Pick up the incorrect statement from the following:
    (A) The process of decomposing the organic matter under controlled anaerobic conditions, is called sludge digestion
    (B) Sludge digestion is carried out in sludge tank
    (C) The gases produced in sludge digestion process, contain 75% carbon dioxide
    (D) The gases produced in sludge digestion process, contain 75% methane

4. The sewer pipes
    (A) Carry sewage as gravity conduits
    (B) Are designed for generating self-cleansing velocities at different discharge
    (C) Should resist the wear and tear caused due to abrasion
    (D) All the above

5. 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

6. 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) All the above

7. 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

8. Pick up the incorrect statement from the following for allowing workers to enter sewers
    (A) The particular manhole and one manhole on upstream and one manhole on downstream should remain open for 30 minutes
    (B) Proper tests for the presence of poisonous gases must be carried out
    (C) The men entering the manhole should be advised to smoke in the sewer
    (D) Warning signals should be erected

9. For the open drain (N = 0.025) shown in the below figure, the discharge is
Waste Water Engg-Set 02, Question No. 09
    (A) 26.88 cumecs
    (B) 27.88 cumecs
    (C) 28.88 cumecs
    (D) 29.88 cumecs

10. 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

11. 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

12. The normal values of over flow rates for sedimentation tanks using coagulant, ranges between
    (A) 25,000 to 35,000 liters/sqm/day
    (B) 40,000 to 50,000 liters/sqm/day
    (C) 50,000 to 60,000 liters/sqm/day
    (D) 80,000 to 100,000 liters/sqm/day

13. 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 Ps = 900/(t + 60) the maximum run off is
    (A) 0.10 cumec
    (B) 0.12 cumec
    (C) 0.15 cumec
    (D) 0.20 cumec

14. 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

15. The rational formula for peak drainage discharge, was evolved by
    (A) Fruhling
    (B) Lloyd David
    (C) Kuichling
    (D) All of these

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