A pilot study on the antimicrobial efficacy of a novel UV-LED system against drainage stack bioaerosol emissions during flushing episodes

Inactivation of airborne microorganisms by ultraviolet (UV) light has been considered one of the most effective procedures among disinfection methods. Ultraviolet light-emitting diodes (UV-LEDs) have a unique place as an emerging technology in air disinfection processes because of their rapid effectiveness and lack of material deterioration. In this study, the efficacy of high-power 285 nm UV-LEDs was explored for Escherichia coli (E. coli) (ATCC15597) inactivation in drainage stack airflow under continuous- and pulsed-UV irradiation conditions. Most relevant photoelectric properties influencing the device operation and performance, including duty cycles and input voltage, were thoroughly investigated. Antimicrobial efficiency varied from 29.0% to 88.0%. The antimicrobial efficiency of pulsed UV irradiation at different duty cycles but the same UV dose was similar. Antimicrobial efficiency was positively correlated with input voltage but negatively correlated with airflow velocity. Moreover, antimicrobial efficiency increased almost linearly with input power per airflow volume (P/Q_a). The estimated Z-values of E. coli ranged from 0.0027 to 0.0341 cm²/µJ, and about 29–370 μJ/cm² of UV dose can be used to obtain one-log inactivation of E. coli, depending on the experimental conditions. The results of this investigation indicate that UVB units can inactivate gastrointestinal drainage stack bioaerosols effectively. This study provides critical information and guidelines for disinfecting drainage stacks with UV, which may aid pathogen infection control in public environments during outbreaks.