![[logo] US EPA](../gif/logo_epaseal.gif){kind=logo}
Disinfection Byproducts: A Reference Resource
Disinfection byproducts are formed when disinfectants used in water treatment plants 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.
------------------------
Trihalomethanes (THM) are a
group of four chemicals that are formed along with other disinfection byproducts
when chlorine or other disinfectants used to control microbial contaminants in
drinking water react with naturally occurring organic and inorganic matter in
water. The trihalomethanes are chloroform, bromodichloromethane,
dibromochloromethane, and bromoform. EPA has published the
Stage 1 Disinfectants/Disinfection Byproducts Rule to regulate
total trihalomethanes (TTHM) at a maximum allowable annual average level of 80 parts per
billion. This standard will replace the current standard of a maximum
allowable annual average level of 100 parts per billion in December 2001 for
large surface water public
water systems. The standard will become effective for the first time in
December 2003 for small surface water and all ground water systems.
------------------------
Haloacetic Acids (HAA5) are a group of
chemicals that are formed along with other disinfection byproducts when chlorine or
other disinfectants used to control microbial contaminants in drinking water
react with naturally occurring organic and inorganic matter in water. The
regulated haloacetic acids, known as HAA5, are: monochloroacetic acid,
dichloroacetic acid, trichloroacetic acid, monobromoacetic acid, and
dibromoacetic acid. EPA has published the Stage 1
Disinfectants/Disinfection Byproducts Rule
to regulate HAA5 at 60 parts per billion annual average.
This standard will become effective for large surface water public water systems in
December 2001 and for small surface water and all ground water public water
systems in December 2003.
------------------------
Bromate is a chemical that
is formed when ozone used to disinfect drinking water reacts with naturally
occurring bromide found in source water. EPA has established the Stage 1
Disinfectants/Disinfection Byproducts Rule to regulate bromate at annual average of 10
parts per billion in drinking water. This standard will become effective for
large public water
systems by December 2001 and for small surface water and all ground public
water systems in December 2003.
------------------------
Chlorite is a byproduct
formed when chlorine dioxide is used to disinfect water. EPA has published the
Stage 1
Disinfectants/Disinfection Byproducts Rule to regulate chlorite at a monthly average level
of 1 part per million in drinking water. This standard will become effective
for large surface water public water systems in
December 2001 and for small surface water and all ground water public water
systems in December 2003.