Corrosion in Drinking Water Distribution Systems:  A Major Contributor of Copper and Lead to Wastewaters and Effluents

Abstract

Corrosion, even in water supply systems with treatment to reduce it, can be a major contributor of copper and lead to both treated municipal (publicly owned treatment works, POTW) wastewater effluents and biosolids. Lead and copper concentrations were measured at several points in the water/wastewater systems of four Massachusetts municipalities. Domestic wastewater was found to contain concentrations of lead and copper significantly higher (p < 0.05) than those in source waters. For each facility, the median concentration of Cu in domestic wastewater was a substantial fraction of the median concentration found in the influent to the POTWs with ratios of 0.36, 0.41, 0.65, and 1.25 for Gardner, New Bedford, Fall River, and Clinton, respectively. The values for lead, in the same order, were 0.28, 0.19, 0.17, and 0.69 (this last ratio based on mean values). Data from the study indicate that minimizing influent concentrations of Cu and Pb to POTWs is an important control factor since the finding of constant removal efficiency for these two constituents means that the higher their concentrations in the influent, the higher they will be in the effluent. These observations strongly support the concern that corrosive drinking water contributes substantially to exceeding, at a minimum, water quality criteria for copper, where dilution of wastewater effluents is low. In turn, this argues for corrosion reduction efforts in water supply systems and the means by which such controls are effected to consider impacts on wastewater as well, which generally is not now done.