Class 7 Biology Wastewater Story Sewage


  • Wastewater released by homes, industries, hospitals, schools and other users is called
  • Rainwater which run down the street during a storm or heavy rain is also included under sewage.

Fig. Sewage  

  • Harmful substances are present in the water which washes off roads and rooftops.
  • Sewage is a liquid waste which contains dissolved and suspended impurities known as

Fig. Contaminants in water

  • Contaminants include organic impurities, inorganic impurities, nutrients, bacteria and other microbes.

Organic impurities include human faces, animal waste.

Inorganic impurities include nitrates, phosphates.

Nutrients include nitrogen and phosphorous.

Bacteria include cholera causing microbe.

Other microbes include dysentery,hepatitis causing organisms.

  • Sewers are the network of small and big pipes forming sewerage.

Fig. Sewers

  • Sewerage is a transport system that carries sewage from the point of being produced to the point of disposal.
  • During the treatment of waste water solids like faeces settle down at the bottom and are removed with a scraper called as

Fig. Sludge

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