Lead service lines (LSLs) connecting water mains to households are a major source of lead in drinking water. More than 50% of LSLs that remain in use in the United States are in the Midwest and Great Lakes regions. While the replacement of LSL is an ongoing process, drinking water suppliers can adjust the water chemistry for corrosion control. Sodium silicates can be used as a potential corrosion inhibitor for lead. Long-term loop experiments were carried out to investigate the role of sodium silicate in limiting lead release from LSLs. Harvested lead pipes were procured from Buffalo, NY for this study. The pre-existing lead- and aluminum-rich scales in these pipes are representative of many scales on LSLs in the Great Lakes region. The pipes were recirculated with baseline water chemistry (dissolved inorganic carbon 24 mg/L C, pH 7.7, 1.1 mg/L Cl<sub>2</sub>) similar to that provided in Buffalo. Conditioning of these pipes with baseline water was followed by treatment with 20 mg/L SiO<sub>2</sub> of sodium silicate. Lead in the water was analyzed using inductively coupled plasma mass spectroscopy (ICP-MS). Scale characterization was carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. Within a few weeks of the treatment with sodium silicate, lead concentrations decreased to below 15 ppb. Periodic assessments of the scale by SEM found that the low lead concentrations were associated with the accumulation of silica in the pipe scales. In this study, several factors that can influence lead release in the presence of sodium silicate were also investigated. The results of these experiments provide insights into the mechanism of lead corrosion inhibition by sodium silicates and can guide recommendations for the use of sodium silicates for corrosion control.

Control of lead release from lead service lines with sodium silicate addition

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.