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  1. The amount of residual chlorine left in public water supply for safety against pathogenic bacteria is about

  2. A.

     0.01 to 0.05 ppm

    B.

     0.05 to 0.5 ppm

    C.

     0.5 to 1.0 ppm

    D.

     1.0 to 5.0 ppm

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  3. Which of the following retards the self purification of stream?

  4. A.

     Higher temperature

    B.

     Sunlight

    C.

     Satisfying oxygen demand

    D.

     None of the above

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  5. As compared to rapid sand filters, slow sand filters give
    (i) Slower filtration rate
    (ii) Higher filtration rate
    (iii) Lesser efficiency in removal of bacteria
    (iv) Higher efficiency in removal of bacteria
    The correct answer is

  6. A.

     (i) and (ii)

    B.

     (ii) and (iii)

    C.

     (i) and (iv)

    D.

     (ii) and (iv)

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  7. The amount of coagulant needed for coagulation of water increases with
    (i) Increase in turbidity of water
    (ii) Decrease in turbidity of water
    (iii) Increase in temperature of water
    (iv) Decrease in temperature of water
    The correct answer is

  8. A.

     (i) and (ii)

    B.

     (i)and(iv)

    C.

     (ii) and (iii)

    D.

     (ii) and (iv)

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  9. Cleaning is done by
    (i) Scraping and removal in filters slow sand
    (ii) Back washing in slow sand filters
    (iii) Scraping and removal in filters rapid sand
    (iv) Back washing in rapid sand filters
    The correct answer is

  10. A.

     (i) and (ii)

    B.

     (ii) and (iii)

    C.

     (i) and (iv)

    D.

     (ii) and (iv)

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  11. Sludge volume index is defined as the ratio of

  12. A.

     Percentage of sludge by volume to percentage of suspended solids by weight

    B.

     Percentage of sludge by volume to percentage of total solids by weight

    C.

     Percentage of suspended solids by weight to percentage of sludge by volume

    D.

     Percentage of total solids by weight to percentage of sludge by volume

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  13. The maximum permissible limit for fluoride in drinking water is

  14. A.

     0.1 mg/liter

    B.

     1.5 mg/liter

    C.

     5 mg/liter

    D.

     10 mg/liter

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  15. Facultative bacteria are able to work in

  16. A.

     Presence of oxygen only

    B.

     Absence of oxygen only

    C.

     Presence as well as in absence of oxygen

    D.

     Presence of water

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  17. The minimum dissolved oxygen which should always be present in water in order to save the aquatic life is

  18. A.

     1 ppm

    B.

     4 ppm

    C.

     10 ppm

    D.

     40 ppm

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  19. The dissolved oxygen level in natural unpolluted waters at normal temperature is found to be of the order of

  20. A.

     1 mg/liter

    B.

     10 mg/liter

    C.

     100 mg/liter

    D.

     1000 mg/liter

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