UV Inactivation of Common Pathogens and Surrogates Under 222 nm Irradiation from KrCl* Excimer Lamps

Germicidal ultraviolet (UV) devices have been widely used for pathogen disinfection in water, air, and on food and surfaces. Emerging UV technologies, like the krypton chloride (KrCl*) excimer emitting at 222 nm, are rapidly gaining popularity due to their minimal adverse effects on skin and eyes compared with conventional UV lamps emitting at 254 nm, opening opportunities for UV disinfection in occupied public spaces. In this study, inactivation of seven bacteria and five viruses, including waterborne, foodborne and respiratory pathogens, was determined in a thin-film aqueous solution using a filtered KrCl* excimer emitting primarily at 222 nm. Our results show that the KrCl* excimer can effectively inactivate all tested bacteria and viruses, with most microorganisms achieving more than 4-log (99.99%) reduction with a UV dose of 10 mJ cm⁻². Compared with conventional UV lamps, the KrCl* excimer lamp exhibited better disinfection performance for viruses but was slightly less effective for bacteria. The relationships between UV sensitivities at 222 and 254 nm for bacteria and viruses were evaluated using regression analysis, resulting in factors that could be used to estimate the KrCl* excimer disinfection performance from well-documented UV kinetics using conventional 254 nm UV lamps. This study provides fundamental information for pathogen disinfection when employing KrCl* excimers.     

APPLICATION OF PHOTODYNAMIC OXIDATION TO THE DISINFECTION OF TAPWATER, SEA WATER, AND SEWAGE CONTAMINATED WITH POLIOVIRUS

Abstract. Poliovirus when added to tapwater, sewage or seawater was readily photoinactivated by methylene blue and visible light. Typically, almost 2.5 logs of virus could be inactivated upon a 5-min exposure to 670 nm light (20 W/m²) in solutions containing 13 μ M methylene blue at pH 10.0. A biphasic inactivation curve was produced for poliovirus, regardless of dye concentration, pH, temperature, sensitization time, nature of suspending solution or sequence of light exposure. These results indicated that a multi-hit inactivation event was occurring. Preincubation of the dye-virus mixture at 24°C increased the rate of virus photoinactivation. Dye concentrations above 26 μ M have little advantage in increasing the amount of virus photoinactivated. Significant inactivation of the virus in the dark occurred at high dye concentrations (52–130μ M ).