An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

Reviewing Treatment Methods for Six-Year Review of Drinking Water Standards

Drinking Water Treatment PlantWhen EPA promulgates a national primary drinking water regulation, it lists “best available technologies (BAT)” recommendations for drinking water treatment processes. To be a BAT, the treatment technology must meet several criteria such as having demonstrated consistent removal of the target contaminant under field conditions. The purpose of the treatment methods feasibility review is to ascertain that there are technologies that meet BAT criteria when a maximum contaminant levelHelpmaximum contaminant levelThe highest level of a contaminant that is allowed in drinking water as delineated by the National Primary Drinking Water Regulations. These levels are based on consideration of health risks, technical feasibility of treatment, and cost-benefit analysis. (MCL) can be lowered.

Several regulations do not specify contaminant MCLs, but instead require that a certain "treatment technique" standard be used. When there is no reliable method that is economically and technically feasible to measure a contaminant at concentrations to indicate there is not a health concern, EPA sets a treatment technique rather than an MCL. A treatment technique is an enforceable procedure or level of technological performance which public water systems must follow to ensure control of a contaminant. The following contaminants have a treatment technique required in lieu of an MCL:
  • acrylamide,
  • copper,
  • Cryptosporidium,
  • epichlorohydrin,
  • Giardia lamblia,
  • lead,
  • Legionella,
  • viruses,
  • total coliforms,
  • heterotrophic plate count (HPC), and
  • turbidity.

For these treatment technique regulated contaminants, Six-Year Review examines whether any improved or less expensive technologies are available that are at least as protective of public health as compared to the existing prescribed treatment techniques.