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  • Question
  • Assertion (A) : The minimum self cleansing velocity in the sewer, at least once a day, must be generated.

    Reason (R) : If certain deposition takes place and is not removed, it obstructs free flow and causes further deposition leading to complete blocking of the sewer.


  • Options
  • 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.

  • Correct Answer
  • Both A and R are true and R is the correct explanation of A 


  • Waste Water Engineering problems


    Search Results


    • 1. In case of sewer lines

    • Options
    • A. water test is carried out to check water tightness of the joints
    • B. test for straightness is carried out with the help of a lamp and mirror
    • C. obstruction test is carried out with the. help of smooth ball of diameter 13 mm
    • D. all the above.
    • Discuss
    • 2. In sewage, the solids in mg per litre is

    • Options
    • A. 100 to 500
    • B. 500 to 1000
    • C. 1000 to 1500
    • D. 1500 to 2000
    • Discuss
    • 3. Drop manholes at the junctions of sewer lines, are provided if

    • Options
    • A. invert level of a branch sewer is more than 60 cm that of the main sewer
    • B. sewer line runs along a main road
    • C. ordinary manhole cannot be built
    • D. two sewer lines intersect.
    • Discuss
    • 4. A nuisance is experienced in diluting water if dilution factor is less than

    • Options
    • A. 100
    • B. 60
    • C. 40
    • D. 20
    • E. 10
    • Discuss
    • 5. Pick up the incorrect statement from the following :

    • Options
    • 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.
    • Discuss
    • 6. 3.0 ml of raw sewage is diluted to 300 ml. The D.O. concentration of the diluted sample at the beginning of the test was 8 mg/l. After 5 day-incubation at 20°C, the DO. concentration was 5 mg/l. The BOD of raw sewerage is

    • Options
    • A. 100 mg/l
    • B. 200 mg/l
    • C. 300 mg/l
    • D. 400 mg/l.
    • Discuss
    • 7. The arrangement made for passing the sewer line below an obstruction below the hydraulic gradient lines called

    • Options
    • A. inverted syphon
    • B. depressed sewer
    • C. sag pipe
    • D. all of these.
    • Discuss
    • 8. If a paper moistened with lead acetate for five minutes when placed in manhole turns black. The sewer certainly contains

    • Options
    • A. Hydrogen sulphide
    • B. Carbon dioxide
    • C. Methane
    • D. Oxygen
    • E. None of these.
    • Discuss
    • 9. A safety lamp when inserted in the upper portion of a manhole causes flames. It indicates the presence of

    • Options
    • A. Carbondioxide gas
    • B. Hydrogen sulphide gas
    • C. Methane gas
    • D. Petrol vapours.
    • Discuss
    • 10. To test chemical oxygen demand (C.O.D.) of sewage, organic matter is oxidised by pottassium dichromate in the presence of

    • Options
    • A. Hydrochloric acid
    • B. Sulphuric acid
    • C. Nitric acid
    • D. Citric acid.
    • Discuss


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