in Microbes in Human Welfare by

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  • Sewage is the subset of wastewater
  • The liquid waste arising mainly from domestic and industrial sources is called Sewage.
  • In the most common usage, sewage refers to the municipal wastewater which contains large amounts of organic matter and microbes and many of which are pathogenic.
  • This huge quantity of sewage or urban waste water cannot be discharged directly into natural water bodies like rivers and streams.
  • Sewage is treated in sewage treatment plants before disposal to make it less polluting.
  • Interestingly the treatment of wastewater is conducted by the heterotrophic microbes naturally present in the sewage.
  • This treatment of Sewage is carried out in two stages: (1) Primary treatment – This treatment step of sewage is basically for physical removal of particles – large and small – from the sewage through filtration and sedimentation. (2) Secondary treatment or Biological treatment – After primary treatment, the primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped (associated with fungal filaments to form mesh like structures, reduction of the BOD (Biochemical Oxygen Demand) of the effluent).
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