A Study on the Effect of Integrated Ozone and UVC-LED Approaches on the Reduction of Salmonella typhimurium Bacteria in Droplets

In the wake of the SARS-CoV-2 pandemic, inactivating bioaerosols became a pivotal issue which helps to prevent the transmittance of SARS-CoV-2. Thus, the current study was conducted to investigate a potential inactivating method using both ozone (O₃) and ultraviolet C (UVC). Individual and integrated effects of O₃ and UVC were compared. A solution containing approximately 4~7.3×10⁶ CFU/mL of Salmonella typhimurium bacteria was used to produce bacteria droplets. These droplets were exposed to O₃ and UVC to determine the reduction rate of bacteria. The exposure times were set as 1 and 30 minutes. Ozone concentrations were 100 and 200 ppmv. UVC-LEDs were used as a UVC source. Peak wavelength of the UVC-LED was 275 nm and the irradiation dose was 0.77 mW/cm². In terms of O₃ and UVC-LED interaction, 194 ppmv styrene was used as a target compound to be removed. Considering the O₃ and UVC-LED interaction, the presence of O₃ could reduce the performance of the UVC-LED, and UVC-LED could also reduce significant amount of O₃. The sequence of O₃ and UVC-LED treatment was as follows: O₃ was exposed at first, then UVC-LED, and this order showed the best reduction ratio (>99.9%). Therefore, if O₃ and UVC-LED is used to disinfect Salmonella typhimurium bacteria contained in droplets, bacteria should be separately exposed to O₃ and UVC-LED in order to improve the inactivation efficiency.