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  • Question
  • COD of raw municipal sewage may be in the range of about __________ mg/litre.


  • Options
  • A. 1-2
  • B. 5-10
  • C. 90-120
  • D. 1500-2500

  • Correct Answer
  • 90-120 


  • Environmental Engineering problems


    Search Results


    • 1. Foaming and priming in boiler operation can be reduced by reduction in __________ in feed water.

    • Options
    • A. turbidity
    • B. color (Hazen)
    • C. total solids
    • D. all (a), (b) & (c)
    • Discuss
    • 2. Waste/polluted water discharged from electroplating, blast furnace and coal mining industries contain mainly __________ substances.

    • Options
    • A. radioactive
    • B. organic
    • C. inorganic
    • D. none of these
    • Discuss
    • 3. Noise produced by cooling fans (employed in air cooled heat exchangers or cooling tower) is mainly caused due to the turbulence created by blade passage through air. It can be reduced by use of a slower fan

    • Options
    • A. with greater number of blades.
    • B. of increased diameter.
    • C. both (a) & (b).
    • D. neither (a) nor (b).
    • Discuss
    • 4. Presence of soluble organics in polluted water causes

    • Options
    • A. undesirable plants growth.
    • B. depletion of oxygen.
    • C. fire hazards.
    • D. explosion hazards.
    • Discuss
    • 5. Oil and grease present in an emulsified state in waste water discharged from industries can be removed by

    • Options
    • A. biological oxidation.
    • B. skimming off.
    • C. settling out using chemical reagents.
    • D. chlorination.
    • Discuss
    • 6. Noise level during normal conversation among men is about __________ decibles.

    • Options
    • A. 10
    • B. 45
    • C. 90
    • D. 115
    • Discuss
    • 7. Bacterial aerobic oxidation of polluted water in biological oxidation ponds is done to purify it. Presence of bacteria helps in

    • Options
    • A. coagulation and flocculation of colloids.
    • B. oxidation of carbonaceous matter to CO2.
    • C. nitrification or oxidation of ammonia derived from breakdown of nitrogeneous organic matter to the nitrite and eventually to the nitrate.
    • D. all (a), (b) and (c).
    • Discuss
    • 8. Iron & manganese present in the polluted water is removed by

    • Options
    • A. simple filtration.
    • B. oxidation followed by settling & filtration.
    • C. chemical coagulation.
    • D. chlorination only.
    • Discuss
    • 9. The main industrial source of emission of hydrogen sulphide air pollutant is

    • Options
    • A. petroleum refineries.
    • B. coal based thermal power plants.
    • C. pulp and paper plant.
    • D. metallurgical roasting & smelting plant.
    • Discuss
    • 10. Fresh sewage is __________ in nature.

    • Options
    • A. acidic
    • B. neutral
    • C. alkaline
    • D. highly acidic
    • Discuss


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