Removal of Lead Phosphate Nanoparticles from Drinking Water by Hydrogen Peroxide Photolysis Combined with Point-of-Use Filtration

Abstract

U.S. EPA recently announced the revision of Lead and Copper Rule to establish a new lead action level at 10 µg/L; however, the formation and release of lead phosphate nanoparticles in drinking water are ubiquitous in lead-containing drinking water distribution systems, and these particles are poorly removed by conventional filters, thus making it challenging for lead control in light of the new regulation. To address this urgent issue, this study developed a treatment train combining a hydrogen peroxide photolysis (UV/H2O2) pre-oxidation with a Point-of-Use (POU) filtration to efficiently remove lead phosphate nanoparticles nano-Pb3(PO4)2(s) from drinking water. Results showed that hydroxyl radical produced via UV/H2O2 oxidized divalent nano-Pb3(PO4)2(s) to tetravalent lead dioxide solid PbO2(s) and aggregated them into larger cluster particles, facilitating an efficient removal by a subsequent POU filtration. Without the UV/H2O2 pre-oxidation, the stand-alone POU filtration was ineffective in reducing nano-Pb3(PO4)2(s) concentration below 10 µg/L. Furthermore, the UV/H2O2 pre-oxidation was effective in diverse drinking water chemical conditions at varying levels of pH (6-8), chloride (0-50 mg/L), and alkalinity (0-200 mg/L as CaCO3). Overall, this study provides an urgently needed and promising lead removal technology that is robust to guarantee drinking water safety to consumers.