Role of iron and aluminum coagulant metal residuals and lead release from drinking water pipe materials

Abstract

Bench-scale experiments investigated the role of iron and aluminum residuals in lead release in a low alkalinity and high (> 0.5) chloride-to-sulfate mass ratio (CSMR) in water. Lead leaching was examined for two lead-bearing plumbing materials, including harvested lead pipe and new lead: tin solder, after exposure to water with simulated aluminum sulfate, polyaluminum chloride and ferric sulfate coagulation treatments with 1-25-μM levels of iron or aluminum residuals in the water. The release of lead from systems with harvested lead pipe was highly correlated with levels of residual aluminum or iron present in samples (R² = 0.66–0.88), consistent with sorption of lead onto the aluminum and iron hydroxides during stagnation. The results indicate that aluminum and iron coagulant residuals, at levels complying with recommended guidelines, can sometimes play a significant role in lead mobilization from premise plumbing.

Keywords:

• Aluminum sulfate
• coagulant residual
• drinking water
• ferric sulfate
• lead corrosion
• polyaluminum chloride

Acknowledgments

The authors would like to acknowledge research support staff at Dalhousie University (Halifax, Nova Scotia, Canada), specifically Heather Daurie, and Jessica MacKay, and at the JD Kline Water Treatment Plant (Halifax, Nova Scotia, Canada).

Funding

The authors would like to acknowledge and thank the Natural Sciences and Engineering Research Council of Canada (NSERC) for financial support to the NSERC/Halifax Water Industrial Research Chair. Additionally, Alisha Knowles's graduate work was funded by a NSERC Postgraduate Studies Doctoral award (NSERC PGS-D).