Preliminary Treatment: This initial stage includes processes like screening, along with the removal of grit and oil.

Primary Treatment: This phase focuses on the extraction of suspended solids, achieving up to 50% removal, and reducing the BOD level by about 30%.

Secondary Treatment: Often known as Biological Treatment, this step utilizes biological methods to transform dissolved and suspended organic waste into stable solids, which are then removed through settling.

Tertiary Treatment: The final stage employs a combination of physical, chemical, and biological processes to eliminate remaining suspended and dissolved solids.