Differences in the Inactivation of Legionella pneumophila Serogroups Using UV-C LED Technology in Drinking Water
Citation:
Buse, H., J. Hall, G. Hunter, AND J. Goodrich. Differences in the Inactivation of Legionella pneumophila Serogroups Using UV-C LED Technology in Drinking Water . Presented at 2021 IUVA World Congress, Cincinnati, OH, June 07 - 08, 2021.
Impact/Purpose:
UV light emitting diodes (LEDs) is an emerging water treatment technology and has been shown to effectively inactivate pathogens. EPA is working in collaboration with manufacturers and expert consultants in this field to evaluate efficiency of these technologies for Legionella pneumophila inactivation in drinking water systems.
Description:
Legionella pneumophila (Lp) is an opportunistic pathogen that causes respiratory infections primarily through inhalation of contaminated aerosols. Lp can colonize premise plumbing systems due to favorable growth conditions found within those environments (e.g. lower disinfectant residual, stagnation, warm temperatures). There are 15 serogroup(sg)s of Lp, all of which have been associated with clinical cases, but sg1 is the predominate disease-causing sg. UV light emitting diodes (LEDs) is an emerging water treatment technology and has been shown to effectively inactivate various drinking water pathogens. In this study, inactivation of four Lp strains (three clinical sg1, 4, and 6 isolates and one sg1 drinking water isolate) were evaluated using a UVC-LED collimated beam. Three wavelengths (250, 265, and 280nm) and six fluence rates (0.5-34 mJ/cm2) were evaluated for each strain in filtered, dechlorinated drinking water. Based on the log inactivation curves, at 255nm, the sg4 and sg6 clinical isolates were more susceptible to inactivation (5.7-5.8 log reduction at 2 mJ/cm2) compared to the two sg1 isolates (5.7-6.1 log10 reduction at 5 mJ/cm2). Interestingly, at 265 nm and a fluence of 5 mJ/cm2, the sg1 and sg4 clinical isolates were more resistant to inactivation (2.4- and 2.6-log reduction, respectively) compared to the sg6 clinical and sg1 drinking water isolates (4.9- and 6.0-log reduction). Similar results were observed at 280 nm where the sg1 and sg4 clinical isolates displayed only a 3.0-log reduction at 16 mJ/cm2. While a 5.1- and 6.0-log reduction was observed for the sg6 clinical and sg1 drinking water isolate, respectively, at the same fluence rate. Results from this study indicate that although UVC-LED disinfection is highly effective, variations in Lp inactivation and wave lengths should be considered especially when targeting specific serogroups and isolates within premise plumbing systems. Additional efficacy testing is being performed using a UVC-LED point of entry, flow-through device.