Chromium 6

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Context for Regulating Chromium 6

Sources of Chromium 6

  • Natural occurrence from certain geologic formations
  • Industrial contamination –localized areas
  • Not typical in surface water sources, but present in some groundwater

Drinking water standard for Total Chromium since 1977

  • This has been a surrogate for Chromium 6
  • Federal MCL = 100 parts per billion (ppb, also μg/L)
  • California MCL = 50 ppb

A Specific MCL for Chromium 6

  • CDPH proposed a Chromium 6 MCL of 10 parts per billion August 2013
  • The MCL was approved and became effective July 1 2014

What are the options for achieving Chromium-6 MCL compliance?


  • Use of other sources
  • Blending with non-impaired sources


  • Best Available Technologies (BATs) include:
  • Ion Exchange
  • Coagulation Filtration (with upstream reduction)
  • Reverse Osmosis