Evaluation of Bactericidal Efficacy, Load, and Safety of Ozonated Water under Overflow Conditions — Development of a Continuous Flow Immersion Method Using Low-Concentration Ozonated Water—

Ozonated water exhibits strong bactericidal properties and is widely applied in medical and food sanitation settings. However, conventional systems often dispense ozonated water from above through a discharge pipe, causing it to flow off the surfaces of the target objects. This results in insufficient contact time and limited surface coverage, thereby reducing disinfection efficacy. In this study, we developed a novel disinfection approach—continuous flow immersion method using low- concentration ozonated water—designed to enhance bactericidal activity even at low ozone concentrations. Test specimens inoculated with representative pathogenic bacteria (Staphylococcus aureus and Escherichia coli) were fully immersed in ozonated water, which was continuously supplied from the bottom of a container and allowed to overflow from the top. This setup ensured sustained contact and circulation, leading to significant microbial reduction. We further examined the impact of ozone-reactive organic matter, observing that ozone activity recovered over time after initial consumption. Airborne ozone concentrations remained at 0.05 ppm, confirming the system's compliance with safety standards for human exposure. These findings demonstrate that the continuous flow immersion method using low-concentration ozonated water enables effective and safe disinfection with low-concentration ozonated water, offering a promising alternative to conventional methods.