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Disinfection Byproducts

Water systems commonly add chlorine to drinking water to kill or inactivate harmful organisms in a process called “disinfection.” During the disinfection stage of the water treatment process, chlorine reacts with naturally occurring total organic carbon (TOC). The TOC are left over after organic materials such as leaf litter, break down in rivers, lakes, and streams. When chlorine reacts with TOC, disinfection by -products (DBPs) are created.

An infographic explaining the formation of Disinfection Byproduct (DBP) when chlorine reacts with natural organic matter in water.

Why is drinking water disinfected?

Disinfecting the water supply is critical to protect the public from disease -causing microorganisms. Chlorine is the most commonly used disinfectant. Drinking water is disinfected to kill bacteria, viruses, and other organisms that can cause serious illnesses and death. Since the early 1900’s, water has benefited public health enormously by lowering the rates of infectious diseases spread through untreated water.

Do the benefits of chlorination outweigh the health risks of DBPs?

Yes. Adding chlorine to drinking water makes the water safer to drink. When used correctly, chlorine kills or inactivates harmful microorganisms that cause diseases, such as E. coli infection, typhoid, cholera and dysentery.

Is chlorination the best disinfectant for my water system?

The immense benefits of reducing infectious diseases, and the simplicity and low cost of water treatment using chlorine, makes chlorination the most appropriate disinfectant for most water systems.

What Are Haloacetic Acids (HAA)?

Haloacetic acids or HAA5 are a group of five DBPs that are created when chlorine and/or chloramine react with naturally occurring organic matter (TOC) found in certain water supplies during treatment. The resulting HAA5 compounds include:

  • Trichloroacetic acid
  • Monochloroacetic acid
  • Bromoacetic acid
  • Dibromoacetic acids
  • Dichloroacetic acid

For More Information About Dbp Regulations And Requirements:


State of California

Local Compliance Agency

Additional questions or concerns:

You may also reach out directly to CCWD staff by contacting:

  • Damon Wyckoff, Director of Operations (209-754-3306, or email
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