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The domestic sewage in large cities:

  1. A
    Have very high amounts of suspended solids and dissolved salts.
  2. B
    Has a high BOD as it contains both aerobic and anaerobic bacteria.
  3. C
    Is processed by aerobic and then anaerobic bacteria in the secondary treatment in Sewage Treatment Plants (STPs).
  4. D
    When treated in STPs does not really require the aeration step as the sewage contains adequate oxygen.

Solution & Step-by-step Explanation

Secondary treatment of sewage involves two main biological steps:Aerobic treatment: Large aeration tanks where aerobic microbes (flocs) reduce the BOD.Anaerobic treatment: Settled sludge is passed into anaerobic sludge digesters where anaerobic bacteria produce biogas.

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The domestic sewage in large cities:
A
Have very high amounts of suspended solids and dissolved salts.
B
Has a high BOD as it contains both aerobic and anaerobic bacteria.
C
Is processed by aerobic and then anaerobic bacteria in the secondary treatment in Sewage Treatment Plants (STPs).
D
When treated in STPs does not really require the aeration step as the sewage contains adequate oxygen.

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Microbes in Human WelfareSewage

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