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Classify the steps appropriately:
  
Answer variants:
After the removal of large objects, the wastewater is sent to the grit and sand removal tank.
Hence, Chlorine gas or ozone gas is often introduced in this water to purify it chemically.
To remove the large objects like plastic bottles, napkins, rags, cans and sticks, the wastewater is first passed through the bar screens.
The water is then removed from the top by machines or sand drying beds as the activated sludge is 97% water.
The water is now sent to the tank which is sloped in the centre, known as clarifier.
  
Separation of large objects from the wastewater: 
  
  
Separation of Girt and Sand particles:
 
  
Removal of solids:
  
  
Removal of suspended sludge:
  
  
Chemical treatment of wastewater: