Drinking water often needs disinfection to maintain water quality and protect public health. Surface water is especially vulnerable to organisms that may cause various diseases. Many water systems add chlorine or other disinfectants for treatment to destroy or inactivate microbial organisms. All disinfectants have advantages and disadvantages depending on the reason for disinfection. For information about other disinfectants, download Alternate Disinfectants 331-252 (PDF).
Disinfectants used for water treatment include the following.
- Chlorine: Added to the water supply as a gas or in the form of hypochlorite either as liquid or solid. More information is available on our Chlorination page.
- Chloramines: These are formed by a combination of chlorine (from gas or hypochlorite) and ammonia.
- Chlorine dioxide (ClO2): This compound is always produced on-site using sodium chlorite and either chlorine or hydrochloric acid.
- Ozone (O3): This compound is produced by an electrical discharge through air or oxygen.
- Ultraviolet Radiation (UV): This is a non-chemical method of disinfection by using ultraviolet radiation at certain wavelengths.
All disinfection treatment processes need to be monitored. If you use chlorine you can refer to our Chlorination Monitoring and Reporting page. If you use another disinfectant please check with your design engineer or your regional engineer.
Chlorine is added to drinking water to kill or inactivate harmful organisms that cause various diseases. Most disinfectants containing chlorine form disinfection byproducts (DBPs) when they react with naturally occurring organic substances in the water. The most common DBPs formed when chlorine is used are trihalomethanes (THMs), and haloacetic acids (HAAs). More information is available on our Disinfection Byproducts page.