Volume 101, Issue 7     July 2009    ISSN 1551-8833

Lead and Copper Rule (LCR) compliance monitoring is intentionally biased toward sites that exhibit elevated lead rather than elevated copper, but water utilities—especially those with higher percentages of newer copper piping—need to be aware that copper concentrations above the action level (AL) may be present in their systems. Orthophosphate doses at sufficient concentrations can help high-alkalinity groundwater systems (even those with new plumbing) meet the copper AL.

The theoretical cupric-hydroxide copper-solubility model predicts that as pipe ages, tenorite or malachite forms and predominates as the surface phase, lowering copper levels. Orthophosphate dosing, however, can prevent the reduction of copper solubility over years and decades, with the result that systems which do not use corrosion inhibitors likely will experience copper levels lower than what would be achieved with orthophosphate. Using the information presented here, water suppliers will be better able to evaluate the tradeoff between orthophosphate treatment versus pH and/or alkalinity adjustment to meet the LCR.—MPM