Operator terms · Water and wastewater
What is disinfection in water treatment?
Disinfection is the step that kills or inactivates disease-causing organisms so water is safe. In drinking water it usually means chlorination, with enough contact time and a lasting residual. In wastewater it treats the effluent before discharge. It is the final safety barrier, not a substitute for earlier treatment.
Last reviewed 2026-08-03
How it works
A disinfectant, most often chlorine, is added at a dose and given contact time so it inactivates pathogens. In drinking water a residual is carried onward to keep protecting the water.
The last barrier
Disinfection is the final safety step, but it relies on earlier treatment removing particles first, since cloudy water shields organisms from the disinfectant.
Common questions
- What is used to disinfect?
- Most commonly chlorine, with enough contact time and a residual.
- Is disinfection the only treatment needed?
- No. It relies on earlier steps removing particles first.
- Does wastewater get disinfected?
- Yes, the treated effluent is disinfected before discharge.