California’s existing 50 µg/L total chromium MCL is to remain in
With five critical groundwater sources having Cr(VI) concentrations between 7 and 40 µg/L that would potentially be impacted
by the new MCL, the Soquel Creek Water District (District) proactively conducted a 2011 paper-based study considering technologies that might be best suited for Cr(VI) treatment at their wells.
After initial monitoring, an MCL of 10 µg/L of Cr(VI) triggers
implementation of quarterly compliance monitoring at individual water sources or entry points to the distribution system
after treatment. Compliance with the MCL is determined by a
running annual average of quarterly samples. The new rule
does not include a compliance implementation schedule and
was technically enforceable as soon as the MCL was finalized.
Treatment with Strong
Base Anion Exchange
Mary Smith, Water Research Foundation; Chad Seidel and Craig Gorman, Corona
Environmental Consulting; and Taj Dufour, Soquel Creek Water District
On July 1, 2014, many California utilities faced a new reality as the Department of Drinking Water (DDW) of the California State Water Resources Control Board adopted the nation’s first hexavalent chro- mium (Cr[VI]) maximum contaminant level (MCL) for drinking water.