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Civil Engineering :: Waste Water Engineering

  1. The minimum recommended diameter of sewers, is

  2. A.

    5 cm

    B.
    10 cm
    C.

    15 cm

    D.

    20 cm.

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  3. Aerobic bacterias

  4. 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.

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

  6. A.

    30 litres/person/year

    B.

    25 litres/person/year

    C.

    30 litres/person/month

    D.
    25 litres/person/month.

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  7. 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

  8. A.
    200 ppm
    B.

    225 ppm

    C.
    250 ppm
    D.

    None of these.

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

  10. A.
    D
    B.
    1.25 D
    C.

    1.5 D

    D.

    1.75 D

    E.

    D.

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  11. If the diameter of sewer is 225 mm, the gradient required for generating self cleansing velocity, is

  12. A.

    1 in 60

    B.
    1 in 100
    C.

    1 in 120

    D.

    none of these.

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  13. Pick up the correct statement from the following :

  14. 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.

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

  16. A.

    centrifugal pump

    B.

    reciprocating pump

    C.

    pneumatic ejector

    D.
    none of these.

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  17.  

     

    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.

  18. 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.

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

  20. A.

    0.68 m

    B.
    0.88 m
    C.

    1.36 m

    D.

    1.76 m.

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