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  1. The detention period for oxidation ponds is usually kept as

  2. A.

     48 hours

    B.

     24 hours

    C.

     10 to 15 days

    D.

     3 months


  3. If the sewage contains grease and fatty oils, these are removed in

  4. A.

     Grit chambers

    B.

     Detritus tanks

    C.

     Skimming tanks

    D.

     Sedimentation tanks


  5. The design discharge for the separate sewer system shall be taken as

  6. A.

     Equal to dry weather flow (DWF)

    B.

     2 × DWF

    C.

     3 × DWF

    D.

     6 × DWF


  7. The design discharge for the combined sewer system shall be taken as

  8. A.

     Equal to rainfall

    B.

     Rainfall + DWF

    C.

     Rainfall + 2 DWF

    D.

     Rainfall + 6 DWF


  9. The major disadvantage of lime soda process of water softening is that

  10. A.

     It is unsuitable for turbid and acidic water

    B.

     Huge amount of precipitate is formed which creates a disposal problem

    C.

     The effluent cannot be reduced to zero hardness

    D.

     It is unsuitable for softening the water of excessive hardness


  11. Assertion A: Slow sand filters are more efficient in removal of bacteria than rapid sand filters.
    Reason R: The sand used in slow sand filters is finer than that in rapid sand filters
    Select your answer based on the coding system given below:

  12. A.

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

    B.

     Both A and R is true but R is not the correct explanation of A

    C.

     A is true but R is false

    D.

     A is false but R is true


  13. Which of the following sewers is preferred for combined system of sewage?

  14. A.

     Circular sewer

    B.

     Egg shaped sewer

    C.

     Rectangular sewer

    D.

     None of the above


  15. The settling velocity of a particle in a sedimentation tank increases if

  16. A.

     Particle size is decreased

    B.

     The surface area of tank is increased

    C.

     The depth of tank is decreased

    D.

     None of the above


  17. Air binding phenomena in rapid sand filters occur due to

  18. A.

     Excessive negative head

    B.

     Mud ball formation

    C.

     Higher turbidity in the effluent

    D.

     Low temperature


  19. The chemical most commonly used to increase speed of sedimentation of sewage is

  20. A.

     Sulphuric acid

    B.

     Copper sulphate

    C.

     Lime

    D.

     Sodium permanganate