EVALUATING LOG REDUCTION OF ESCHERICHIA COLI ON STAINLESS STEEL USING OZONE AND CHLORINE DIOXIDE GAS

This study evaluated the inactivation of Escherichia coli ATCC 11229 strain AMC 198 inoculated onto stainless-steel coupons using ozone gas at different concentrations and relative humidity levels. It also assessed the disinfection efficacy of ozone and chlorine dioxide gas at equivalent oxidative concentration. Treatments for ozone gas were performed at 15, 50, 75, 100, and 125 ppmv under relative humidity levels of 66.8 ± 0.6%, 75.3 ± 1.1%, 91.1 ± 1.3% for an exposure time of 30 minutes. Increasing ozone concentrations achieved a log reduction of 3.6 ± 0.8 using 125 ppmv at 91.1% relative humidity. Statistical results demonstrated that both relative humidity and ozone concentrations had an effect on the inactivation of Escherichia coli ATCC 11229 strain AMC 198. When ozone and chlorine dioxide were compared at equivalent oxidative concentrations, chlorine dioxide reached a log reduction of 4.7 ± 0.3 and 4.6 ± 0.6 for 30 ppmv and 70 ppmv, respectively, under a relative humidity of 91.1%. But under a relative humidity of 66.8 ± 0.6%, ozone and chlorine dioxide achieved similar inactivation. The results confirm that both gases can achieve significant reductions in E. coli, ranging from 3.6 to 4.8 log making them highly effective disinfectants/sanitizers.