Disinfection
The treatment step that inactivates disease-causing microorganisms in water or wastewater.
Disinfection is the treatment step that destroys or inactivates pathogenic microorganisms, the bacteria, viruses, and parasites capable of causing disease. It is the public health heart of water treatment: earlier processes remove particles and prepare the water, but disinfection is the barrier that directly addresses the organisms that make people sick. Wastewater plants also disinfect, protecting the waterways and communities downstream of their discharge.
Several disinfection approaches are in common use. Chlorine-based disinfection is the most widespread and has the important property of providing a lasting residual that continues protecting water as it travels through the distribution system. Ultraviolet light and ozone are also widely used, each with distinct strengths and operational considerations. Real systems often combine methods, and the choice depends on the water, the facility, and regulatory requirements.
For exam candidates, disinfection is among the most heavily emphasized topics in every series, spanning the science of how disinfectants work, the factors that influence their effectiveness, safety around disinfection chemicals, and the operator's responsibility to verify results. The specific doses, contact times, and residual targets used at any actual facility are set by regulation, permits, and process design, and are learned for the individual system.
Common questions
What is the definition of disinfection in water treatment?
Disinfection is the treatment step that inactivates or destroys disease-causing microorganisms, such as bacteria, viruses and parasites, so water is safe to drink or safe to discharge. It is different from sterilization, which kills all microbial life.
What is the meaning of disinfection compared with filtration?
Filtration removes particles from water. Disinfection inactivates the organisms that remain. Drinking water plants use both, with disinfection as the final barrier and a residual (chlorine or chloramine) kept in the distribution system.
What are the common methods of disinfection?
Chlorine, chloramine, chlorine dioxide, ozone and ultraviolet light. Chlorine, chloramine and chlorine dioxide leave a residual in the pipes; ozone and UV do not, so plants using them usually add a chemical residual afterward.
Related terms
| Water treatment | The processes that convert raw source water into safe drinking water, and the certification series covering them. |
| Wastewater treatment | The processes that clean used water before returning it to the environment, and the corresponding certification series. |
| Turbidity | The cloudiness of water caused by suspended particles, a central water quality indicator. |
| Potable water | Water that is safe for people to drink and use in food preparation. |
Sources
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