Utilizing UV LED Disinfection to Decrease Pseudomonas aeruginosa Biofilm Formation in Drinking Water Systems

Abstract

Opportunistic pathogens (OPs), such as Pseudomonas aeruginosa, can form biofilms and proliferate in drinking water distribution systems (DWDS) and building premise plumbing even in the presence of a disinfectant residual and are responsible for the largest number of deaths attributable to waterborne disease in the United States. There is a need for strategies to prevent biofilm formation and therefore the sustained occurrence of OPs throughout DWDS. This study demonstrates how UV LED disinfection (282 nm, 50 mJ/cm²) before entering a distribution system or at a building's point-of-entry can delay the start of detectable biofilm formation for up to 6 days and significantly reduce the concentration of biofilm-bound cells for up to and beyond 8 days compared to untreated controls. Biofilm growth after UV LED disinfection was evaluated on different materials (PTFE, CPVC, and Cu) and under different carbon nutrient conditions (19 mg/L TOC, 100 μg/L C, 250 μg/L C). PTFE supported the highest biofilm growth, followed by CPVC, while Cu supported the least. UV pre-treatment reduced downstream biofilm formation by 0.33–2.42 log CFU/coupon (53.0%–99.6%) on CPVC surfaces over 5–8 days, with more realistic drinking water carbon conditions (100 or 250 μg/L C) increasing efficacy compared to heightened carbon conditions (19 mg/L TOC). These results inform how UV LEDs could be implemented within drinking water infrastructure to aid in biofilm and OP control.