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  • Question
  • The ratio of oxygen available to the oxygen required for stabilisation of sewage is called the


  • Options
  • A. bacterial stability factor.
  • B. relative stability.
  • C. biological oxygen demand (BOD).
  • D. oxygen ion concentration.

  • Correct Answer
  • relative stability. 


  • Environmental Engineering problems


    Search Results


    • 1. Coal washing waste water containing about 3% suspended solids (comprising of clay, slate, stone etc.) is treated for solid particles removal

    • Options
    • A. by chemical coagulation.
    • B. in sedimentation tanks equipped with mechanical scrapper.
    • C. in vacuum filter.
    • D. in clarifiers.
    • Discuss
    • 2. Operating principle of cyclone separator is based on the action of __________ dust particles.

    • Options
    • A. diffusion of
    • B. centrifugal force on
    • C. gravitational force on
    • D. electrostatic force on
    • Discuss
    • 3. Inhalation of lead compounds present in the automobile exhausts (using leaded petrol) causes

    • Options
    • A. blood poisoning.
    • B. anaemia.
    • C. nervous system disorder.
    • D. all (a), (b) and (c).
    • Discuss
    • 4. Maximum allowable concentration of CO2 in air for safe working is __________ ppm (parts per million).

    • Options
    • A. 50
    • B. 1000
    • C. 2000
    • D. 5000
    • Discuss
    • 5. Threshold Limit Value (TLV) is the maximum allowable concentration (i.e. safe limit) of pollutants in air. Safe limit for SO2 in air is __________ ppm.

    • Options
    • A. 5
    • B. 500
    • C. 1000
    • D. 2000
    • Discuss
    • 6. Scale formation in boiler is controlled by

    • Options
    • A. preheating of feed water.
    • B. reduction in hardness, silica & alumina in feed water.
    • C. keeping the pH value of feed water just below 7.
    • D. eliminating H2S in feed water.
    • Discuss
    • 7. Most of the atmospheric air pollutants are present in large quantity in

    • Options
    • A. stratosphere
    • B. thermosphere
    • C. trophosphere
    • D. mesosphere
    • Discuss
    • 8. Replenishment of dissolved oxygen in water stream polluted with industrial waste occurs by

    • Options
    • A. natural aeration of water stream.
    • B. photosynthetic action of algae.
    • C. both (a) & (b).
    • D. neither (a) nor (b).
    • Discuss
    • 9. H2S present in gaseous stream can be removed by adsorption on

    • Options
    • A. silica gel
    • B. active carbon
    • C. bog iron
    • D. limestone powder
    • Discuss
    • 10. Aerobic biological oxidation ponds used for the purification of polluted water

    • Options
    • A. destroys/removes pathogen from the sewage.
    • B. is not very effective for nonbiodegradable substances (e.g. ABS) containing effluents.
    • C. destroys/removes pathogen much more effectively if the sewage is chlorinated.
    • D. all (a), (b) & (c).
    • Discuss


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