UV disinfection has been utilized for many years in water treatment plants as an alternative method to conventional disinfection with chlorine. UV disinfection provides disinfection without any chemical costs and minimal DBP formation risk. With recent advances in the production of UV-LEDs, there is a great opportunity to change the current practice of using mercury lamps to the new UV-LEDs for advantages such as wavelength diversity and quicker start-up time. Given that the regrowth after treatment for mercury lamp is a known issue, it is critical to check UV-LEDs for the possibility of having the same issue with regrowth. The inactivation of two indicator microorganisms (<i>E. coli</i> and MS2) was studied under 254 nm, 278 nm and 305 nm doses in this research. Results demonstrated higher doses required to obtain 3.0 log inactivation than the amount needed for the 254 nm Hg Lamp. Furthermore, results illustrated DOM did not significantly impact disinfection kinetics for all the wavelengths. Regrowth experiments, including dark repair and photoreactivation, were conducted. Results showed DOM can enhance in several cases. Importantly, it was observed for the first time that the photoreactivation mechanism was exhausted after a given fluence followed by the inactivation phase which stresses the importance of light exposure. Moreover, the result indicated that different wavelength has different effects on the photoreactivation with visible light having more regrowth compared to UVA reactivation.

Wavelength dependence of E.coli photoreactivation in the presence of DOM

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.