Enhanced inactivation of E. coli by pulsed UV-LED irradiation during water disinfection.

Pulsed ultraviolet (UV) irradiation has presented enhanced inactivation efficiency in water disinfection and food decontamination. As an emerging UV source, UV light-emitting diodes (UV-LEDs) are an attractive alternative for pulsed irradiation because they can be turned on and off with a high and adjustable frequency. In this study, disinfection efficiencies of pulsed and continuous UV-LED irradiation were compared for Escherichia coli (E. coli) inactivation in water using a high power 285 nm LED and low power 265 and 280 nm LEDs. Factors including various duty cycles, pulse frequencies and UV irradiances were evaluated. The log-inactivation of E. coli increased substantially as the duty cycle decreased from 100% to 5% at the same UV dose. For 265 and 280 nm LEDs, the log-inactivation enhancements of pulsed UV irradiation were similar. When a higher irradiance was applied, the energy efficiency enhancement of pulsed UV irradiation became more obvious. The log-inactivation of E. coli enhanced remarkably using high current pulsed irradiation of 280 nm LEDs. Compared to continuous UV irradiation, pulsed UV-LED irradiation is an attractive alternative for E. coli inactivation in water considering energy efficiency.