Understanding the role of particulate iron in lead release to drinking water

Hi all…lead continues to be the drinking water issue of 2016 as evidenced by the attention it is receiving in the media and will be at the upcoming 17^th National Conference on Drinking Water and CWWA’s 2^nd National Water and Wastewater Conference.  Another interesting article by Graham Gagnon’s research group at DalTech has just appeared in Environmental Science & Technology. The study revealed that “lead release was higher by 96 µg L^-1, on average, from lead service lines supplied by corroded iron compared to the inert reference material (PVC)” and that “increasing orthophosphate from 0.5 to 1.0 mg L^-1 (as PO₄^3-) accompanied an average reduction in lead release of 6 µg L^-1 month^-1 but did not significantly reduce the effect of an upstream iron main.”

The authors conclude that “Given the prevalence of unlined iron distribution mains in many drinking water systems and the significant public health risks posed by low-level lead exposure, an improved understanding of the mechanisms governing lead-iron interactions in this context is important.”

Bill

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Understanding the role of particulate iron in lead release to drinking water

Benjamin F. Trueman and Graham A. Gagnon

Environ. Sci. Technol., Just Accepted Manuscript

DOI: 10.1021/acs.est.6b01153

Publication Date (Web): July 28, 2016

http://pubs.acs.org/doi/abs/10.1021/acs.est.6b01153

Abstract

“Lead service lines (LSLs) are a major source of drinking water lead, and high iron levels are frequently observed along with elevated lead release. A model distribution system, dosed with orthophosphate, was used to evaluate the effect of corroded iron distribution mains on lead release from recovered LSLs. Lead release was higher by 96 µg L^-1, on average, from LSLs supplied by corroded iron compared to the inert reference material (PVC). This effect may be explained by deposition of semiconducting iron oxide particles within LSLs. When galvanic cells with lead and magnetite (Fe₃O₄) electrodes were short-circuited, lead release increased eight-fold and a current averaging 26 µA was observed. In effluent from LSLs with an upstream iron main, colloidal lead and iron occurred in the same size fraction—possibly due to release of colloidal particles from LSL corrosion scale enriched with iron. Under these circumstances, high molecular weight (> 669 kDa) ²⁰⁸Pb and ⁵⁶Fe elution profiles, observed via size-exclusion chromatography, were highly correlated (average R² = 0.97). Increasing orthophosphate from 0.5 to 1.0 mg L^-1 (as PO₄^3-) accompanied an average reduction in lead release of 6 µg L^-1 month^-1 but did not significantly reduce the effect of an upstream iron main.”