Evaluating the efficacy of Cu and Ag ions for the inactivation of Legionella pneumophila
Citation:
Hintz, C., B. Morris, AND Helen Y. Buse. Evaluating the efficacy of Cu and Ag ions for the inactivation of Legionella pneumophila. Ohio Section American Water Works Association, NA, Ohio, September 22 - 25, 2020.
Impact/Purpose:
This abstract highlights the EPA work on opportunistic pathogens in building water systems and will be presented at an local conference. This study aimed to determine the efficacy of copper and silver ions in the inactivation of Legionella pneumophila and the minimal ion concentration needed to achieve inactivation.
Description:
Legionella pneumophila (Lp ) is an opportunistic pathogen that can colonize premise plumbing systems. These systems can serve as a potential source of human infection resulting from the inhalation of contaminated aerosols generated from various devices such as showers, humidifiers, and decorative fixtures. To control Legionella growth in these systems, secondary treatment such as copper (Cu)-silver (Ag) ionization or CSI has been implemented in large premise plumbing systems, but the effectiveness is inconsistent across studies. Here, we are using log10 reduction to evaluate effectiveness of CSI. Target concentrations of Cu and Au were 0.3 ppm Cu and 30 ppb Ag were innoculated with Lp at a final concentration of 6 log10 colony forming units (CFU) mL-1. Samples were collected at 0, 2, 5, and 24 h to determine the time needed for a 3-4 log reduction in Lp CFU mL-1. After 5 h, a greater than 6- log reduction of Lp was observed in the presence of Cu and Ag ions. This work demonstrates the inactivation of Lp under experimental conditions in less than 5 h at concentrations of Cu and Ag that are below the regulatory action levels for drinking water. Future work will evaluate earlier timepoints, the combined effects of Cu and Ag at various concentrations, and the effectiveness of Cu and Ag on the inactivation of different Lp strains. This work is relevant to managers who are responsible for maintaining safe drinking water for the public.