|What is Disinfection?|
|What are Disinfection Byproducts?|
|What Regulations Control Disinfection Byproducts?|
|How are Disinfection Byproducts and Pathogens Related?|
What is Disinfection?
Disinfection is usually a chemical process used in water systems which either chemicals are added to inactivate (or kill) pathogens (i.e., disease causing organisms) found in the source water (i.e., lake, river, reservoir, or ground water aquifer from which water is drawn and treated). Disinfection through inactivation usually involves the use of disinfectants such as chlorine, ozone, and chlorine dioxide, and a combination of chlorine and ammonia (chloramines) may render many of these organisms harmless.
What are Disinfection Byproducts?Disinfection byproducts are formed when disinfectants used in a water treatment react with bromide and/or natural organic matter (i.e., decaying vegetation) present in the source water. Different disinfectants produce different types or amounts of disinfection byproducts. Disinfection byproducts for which regulations have been established have been identified in drinking water, including trihalomethanes, haloacetic acids, bromate, and chlorite.
What Regulations Control Disinfection Byproducts?
In December 1998, EPA published the Stage 1 Disinfectants/Disinfection Byproducts Rule that requires water systems to use treatment methods to reduce the formation of disinfection byproducts and to meet the following standards: total trihalomethanes (TTHM)(measured as the sum concentration of chloroform, bromoform, bromodichloromethane, and dibromochloromethane) at 80 parts per billion (ppb), haloacetic acids (HAA5) (measured as the sum concentration of monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, and dibromoacetic acid) at 60 ppb, bromate at 10 ppb, and chlorite at 1.0 parts per million (ppm). The standards for TTHM, HAA5, and bromate are annual averages. For chlorite, the standard is an average of a three samples taken at least monthly. Data from the ICR and research will be used to consider further disinfection byproduct control under a Stage 2 Disinfectants/Disinfection rule, scheduled to be published in May 2002.
How are Disinfection Byproducts and Pathogens Related?
Current disinfection methods used in water systems can inactivate pathogens, but can also form disinfection byproducts that may be harmful to human health. EPA's job in regulating disinfection byproducts is to develop requirements for water treatment that will both protect people from waterborne disease and the potential harmful effects of disinfection byproducts. The ICR will provide some of the information to address this issue.
|Disinfection Byproducts: A Reference Resource|
|Disinfection Byproduct Health Effects|