Waste water treatment

Hi friends, I would like tell about how waste water can be treated.
Waste water is surface water and this water can be pumped and placed in unit operations.
The main objective of waste water treatment is
1 To remove suspended solids
2 To remove biodegradable matter
3 To kill pathogens

As like as water treatment waste water has some unit operations.

1.Screens: The waste water is collected in screens , in this screens most of the large waste objects are get removed.
2.Grit chamber: In grit chamber we only remove inorganic water present in water..This unit operations is designed in such a way that that inorganic matter can be removed, organic matter wont remove because of it less specific gravity
3.Primary sedimentation tank:
In this unit operation 60% of suspended solids are removed by gravity
4.Aerators: Then the water is sent to aerators.In this unit operation in the presence of oxygen the Dissolved organic matter is converted into flocculated organic matter.
5.Secondary sedimentation tank:In this thr flocculated organic matter are settled by gravity.
6Disinfection: The last unit operation is disinfection .in this the pathogens are killed.
Thanks for reading guys