Inactivation of Escherichia coli and Yersinia enterocolitica attached to water-dispersed microplastics using ultraviolet C light-emitting diode irradiation

The disinfection effect of ultraviolet C light-emitting diode (UVC-LED) irradiation on pathogenic microorganisms attached to microplastic surfaces has not been investigated. This study quantified the effect of UVC-LED irradiation on the inactivation kinetics of Escherichia coli and Yersinia enterocolitica attached to polycarbonate microplastics (PC-MPs). For comprehensive analysis, disinfection was performed under different agitation speeds (0–300 rpm). A UVC-LED dose of 30 mJ/cm2 reduced the E. coli and Y. enterocolitica counts by 2.11 log and 4.32 log, respectively, whereas agitation at 300 rpm promoted corresponding reductions of 4.41 log and 5.68 log. Attachment onto PC-MPs affected UVC-LED-induced inactivation of the two pathogenic bacteria, but the disinfection effect could be increased via stirring. An increase in the stirring speed increased the fluidity of MPs and the frequency of exposure of the MP surfaces to the UVC-LED light source, inducing a synergistic effect on the disinfection of microorganisms attached to the MPs. To better characterize inactivation kinetics under heterogeneous conditions, five mathematical models (log-linear, Weibull, double Weibull, biphasic, and biphasic shoulder) were applied as complementary approaches, with model selection was based on goodness-of-fit criteria. This study has elucidated the UVC-LED disinfection effect on pathogenic microorganisms present on MPs in water treatment processes, thus contributing to future strategies for ensuring food safety.