Control of new copper corrosion in high-alkalinity drinking water

Research and field experience have shown that high-alkalinity waters can be associated with elevated copper levels in drinking water. The objective of this study was to document the application of orthophosphate (PO(4)) to the distribution system of a building with a copper problem associated with high-alkalinity source water. The alkalinity and pH of the water were 273 mg/L calcium carbonate and 7.4, respectively, and copper levels at taps ranged from 1.4 to 2.4 mg/L. Experimental bench-scale jar tests proved to be useful for establishing an appropriate orthophosphate dose. A simple chemical feed system delivered orthophosphate to the building at a dose of approximately 3 mg/L PO(4). Within several weeks, copper levels throughout the building dropped below the Lead and Copper Rule copper action level of 1.3 mg/L. Orthophosphate levels remained consistent across the building and did not change during stagnation. The addition of orthophosphate also increased the chlorine residuals of flushed water samples.