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  • Question
  • 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).

  • Correct Answer
  • both (a) & (b). 


  • Environmental Engineering problems


    Search Results


    • 1. Most of the atmospheric air pollutants are present in large quantity in

    • Options
    • A. stratosphere
    • B. thermosphere
    • C. trophosphere
    • D. mesosphere
    • Discuss
    • 2. 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
    • 3. 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.
    • Discuss
    • 4. 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
    • 5. 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
    • 6. 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
    • 7. 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
    • 8. Polluted water having low BOD are most economically treated in

    • Options
    • A. sedimentation tanks
    • B. oxidation ponds
    • C. sludge digester
    • D. clarifier
    • Discuss
    • 9. Dust collection efficiency of a cyclone separator depends upon its

    • Options
    • A. diameter.
    • B. inlet gas velocity.
    • C. overall height.
    • D. all (a), (b) & (c).
    • Discuss
    • 10. Pick out the wrong statement.

    • Options
    • A. Caustic embrittlement of boiler's metallic parts is caused by high concentration of caustic soda in boiler feed water.
    • B. Cooling and freezing of water kills the bacteria present in it.
    • C. With increasing boiler operating pressure of steam, the maximum allowable concentration of silica in feed water goes on decreasing.
    • D. Dissolved oxygen content in high pressure boiler feed water should be nil.
    • Discuss


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