Inactivation of Airborne Bacteria using Vacuum Ultraviolet Light

Abstract

Airborne bacteria have affected human health significantly, which has attracted much attention recently, and many techniques have been developed for inactivating them. Among the techniques, ultraviolet photocatalytic oxidation (UV PCO) is known as a high-level oxidation treatment because it is more efficient than conventional methods, such as filtration & heat treatment, and is easier to maintain and manage. The most commonly used UV light sources in the UV PCO systems are UVC and UVA, which have wavelengths of 254 nm and 365 nm respectively. Although these UV light sources are known to have high efficiency for inactivating airborne bacteria, they show low photocatalytic efficiency in a short exposure time. Previously, we presented vacuum ultraviolet (VUV) light with photocatalysis for inactivating airborne MS2 phages, and it showed that the VUV PCO system efficiently (overall efficiency: ~90%) inactivated the airborne viruses in a very short reaction time (0.009 s and 33 L/min). In this study, we extended the study to inactivate several airborne bacteria: Pseudomonas fluorescens, Micrococcus luteus, Mycobacterium parafortuitum, and Escherichia coli K-12 by irradiating VUV light onto 2mm pleated Pd-TiO2 photocatalyst. When VUV was applied to airborne Pseudomonas fluorescens for 0.009 second, more than 90% inactivation efficiency was observed, and overall ozone degradation efficiency was 75% or more. The system is expected to be a good alternative to existing UV-based air purifiers.