List of Drinking Water Contaminants & Their Maximum Contaminant Level: Disinfection Byproducts

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List of Drinking Water Contaminants & Their Maximum Contaminant Level: Disinfection Byproducts

Our chart for the drinking water contaminants associated with disinfection byproducts follows below.

These 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 byproducts. Byproducts from the disinfection process for which regulations have been established have been identified in drinking water, including trihalomethanes, haloacetic acids, bromate, and chlorite.

  • Trihalomethanes (THM):
    • A group of four chemicals that are formed along with other disinfection byproducts when chlorine or other disinfectants are 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 replaced the old 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 became effective for the first time in December 2003 for small surface water and all ground water systems.
  • Haloacetic Acids (HAA5):
    • 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 became 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:
    • 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 became effective for large public water systems by December 2001 and for small surface water and all ground public water systems in December 2003.
  • Chlorite:
    • A byproduct formed when chlorine dioxide is used to disinfect water. EPA has published the Stage 1 Disinfectants/Byproducts Rule to regulate chlorite at a monthly average level of 1 part per million in drinking water. This standard became 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.
total_disinfection_byproducts

Total Disinfection Byproducts

 

Drinking Water Contaminants: Disinfection Byproducts
Contaminant MCLG1 (mg/L)2 MCL or TT1 (mg/L)2 Potential Health Effects from Long-Term Exposure Above the MCL (unless specified as short-term) Sources of Contaminant in Drinking Water
Bromate Zero 0.010 Increased risk of cancer Byproduct of drinking water disinfection
Chlorite 0.8 1.0 Anemia; infants & young children: effects nervous system Byproduct of drinking water disinfection
Haloacetic acids (HAA5) n/a6 0.0607 Increased risk of cancer Byproduct of drinking water disinfection
Total Trihalomethanes (TTHMs) –> n/a6 –> 0.0807

 

Liver, kidney or central nervous system problems; increased risk of cancer Byproduct of drinking water disinfection

Notes:

1 Definitions: Maximum Contaminant Level Goal (MCLG) – The level of a contaminant in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety and are non-enforceable public health goals. Maximum Contaminant Level (MCL) – The highest level of a contaminant that is allowed in drinking water. MCLs are set as close to MCLGs as feasible using the best available treatment technology and taking cost into consideration. MCLs are enforceable standards. Maximum Residual Disinfectant Level Goal (MRDLG) – The level of a drinking water disinfectant below which there is no known or expected risk to health. MRDLGs do not reflect the benefits of the use of disinfectants to control microbial contaminants. (TT) Treatment Technique – A required process intended to reduce the level of a contaminant in drinking water. Maximum Residual Disinfectant Level (MRDL) – The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants.

2 Units are in milligrams per liter (mg/L) unless otherwise noted. Milligrams per liter are equivalent to parts per million.

6 Although there is no collective MCLG for this contaminant group, there are individual MCLGs for some of the individual contaminants:
• Trihalomethanes: bromodichloromethane (zero); bromoform (zero); dibromochloromethane (0.06 mg/L): chloroform (0.07mg/L).
• Haloacetic acids: dichloroacetic acid (zero); trichloroacetic acid (0.02 mg/L); monochloroacetic acid (0.07 mg/L). Bromoacetic acid and dibromoacetic acid are regulated with this group but have no MCLGs.

7 Lead and copper are regulated by a Treatment Technique that requires systems to control the corrosiveness of their water. If more than 10% of tap water samples exceed the action level, water systems must take additional steps. For copper, the action level is 1.3 mg/L, and for lead is 0.015 mg/L.

Contact Time

Contact Time

It is somewhat ironic that trying to control drinking water contaminants & contain their maximum contaminant level with disinfection directly leads to disinfection byproducts which can also be harmful to us! Point of the matter is, the more junk we put in our water, the more junk we are likely to get back when we treat it or drink it so stop putting junk in the water already!

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