The treatment piece of this process is called the water-treatment process. The water treatment process INVOLVES four steps, in this order: coagulation, sedimentation, filtration, and disinfection.
Coagulation:In water treatment, coagulation flocculation involves the addition of polymers that clump the small, destabilized particles together into larger aggregate so that they can be more easily separated from the water. 
Sedimentation: Sedimentation is a physical water treatment process USING gravity to remove suspended solids from water.
Filtration:Filtration is any of various mechanical, physical or biological operations that separate solids from fluids by adding a MEDIUM through which only the fluid can PASS. The fluid that passes through is called the filtrate.
Disinfection: Water disinfection means the removal, deactivation or KILLING of pathogenic microorganisms. ... When microorganisms are not removed from drinking water, drinking water usage will cause people to fall ill. Sterilization is a process related to disinfection.