Investigation of the Oxidation Kinetics of Vanadinite by Bromine in Water Distribution Systems

BSC-Ursa Minor 12

Vanadium is being considered for more stringent drinking water standards by regulatory agencies, with the World Health Organization recently issuing an alert level of 15 ppb of dissolved vanadium in drinking water. Vanadium contamination in source water complexes with lead to form Vanadinite Pb₅(VO₄)₃Cl, a lead (II) mineral, which persist and buildup even at very low concentrations of contamination. Studies estimate vanadinite scale level buildup present in lead service lines in current infrastructure to be 2% by weight. This study investigated the kinetics and mechanisms of oxidation of vanadinite by free bromine in drinking water and associated vanadium and lead release. Batch experiments were performed in the pH range of 7.0-10.0. Bromine consumption was not affected by pH unlike other lead corrosion compounds. However progressively filtered samples at 0.2um and 0.025um respectively, analyzed by ICP-MS, indicated that pH did impact vanadium release with overall solubility significantly higher than corresponding released lead species. XRD data confirmed the decreasing concentration of vanadinite and increase of lead oxide over the course but also indicated the possible formation of multiple vanadium species or complexes which may explain the increased solubility and bromine consumption behavior contrary to other lead scale species. The kinetics data obtained from this study suggest that the oxidation of vanadinite by bromine in water distribution systems can contribute to an increase of highly soluble vanadium occurrence in tap water which current filtration systems would be not be effective in removing.