The common process line of a wastewater treatment consists of a pretreatment (reduction of solids), a primary treatment (removal of suspended solids and fats, and/or a physical-chemical treatment) and a secondary treatment (removal organic matter and/or nutrients via biological and/or chemical). Finally, you can also perform a regeneration with a tertiary treatment and disinfection, for those cases where you want to reuse the treated water. Inevitably, water treatment generates a certain amount of sludge which must also be treated.
The technologies used in different processes for the purification of wastewater are numerous, always adapting itself to the needs and context of work required for each particular case.