UV&#x2013;H₂O₂-Based Process for Inactivation of <i>Escherichia coli</i> and <i>Staphylococcus aureus</i> on Inanimate Surfaces: Kinetics Analysis and Relationship between UV Dose and Log Reduction

Abstract

Surface disinfection plays an important role in preventing infectious diseases. The present work deals with disinfecting different contaminated material surfaces by the UV–H2O2 process. Almost 3 log count reduction (99.9%) of Escherichia coli and Staphylococcus aureus on steel-rupee coin surfaces was achieved at a fluence dose of 10 mJ cm−2. For quick, effective disinfection (3 log count reduction), a UV light intensity of 0.10 mW cm−2 should be provided. The rate of the UV–H2O2 process was two times faster than that of the direct UV process. The inactivation of microbes followed a two-step kinetic model. The fluence-based reaction rate constants were 0.4162 (±0.0619) and 0.7486 (±0.1205) cm2 mJ−1 for E. coli and 0.3891 (±0.0455) and 0.9973 (±0.1695) cm2 mJ−1 for S. aureus under direct UV irradiation and the UV–H2O2 process. An H2O2 concentration of 0.05%–0.2% was sufficient for the UV–H2O2 process, and a further increase in H2O2 concentration significantly decreased the inactivation efficiency due to the scavenging of OH• by excess H2O2. Maximum inactivation of microbes was obtained in the case of steel-rupee coin surfaces. The log count reductions of E. coli and S. aureus were 5.15 and 5.65 in 300 s at UV intensity 0.25 mW cm−2 for steel-rupee coin surfaces (UV dose = 75 mJ cm−2). However, no significant difference was found for the disinfection of glass, polished wood, aluminum, plastic, and leather surfaces. Generalized relationships between log reduction and UV irradiation dose were developed and validated through experiments performed to inactivate E. coli and S. aureus on steel-rupee coin surfaces in fabricated automatic surface disinfection equipment to examine the applicability of the relationships. The findings of the study will help to design UV-based surface disinfection units for healthcare, airport luggage handling, and food storage facilities.