Bacteria Inactivation via X-ray-Induced UVC Radioluminescence: Toward in Situ Biofouling Prevention in Membrane Modules.

Germicidal UVC radiation is a highly effective, chemical-free tool for bacteria inactivation, but its application is limited to reactors and open areas that can accommodate lamps/LEDs and wiring. A relevant example of problematic bacterial colonization within UV-inaccessible confines where chemical techniques have found only limited success is biofouling of feed channels in high-pressure membrane elements for water treatment. Herein we demonstrate a unique method of generating UV internally using embedded radioluminescent (RL) particles excited by an external X-ray source. We further show that the magnitude of the emitted UV intensity and required X-ray dose rates are likely within effective and practical ranges for future application to antibiofouling technology. Assessment of three Pr3+-activated RL phosphor candidates revealed LaPO4:Pr3+ to have the most favorable luminescence properties, achieving over 2-log inactivation of E. coli in a thin water film with a 74 Gy dose of 150 kVp X-rays. The effect of UVC RL resulted in a doubling of inactivation rates over X-ray irradiation alone. Further efforts targeting membrane applications, which included X-ray penetration modeling, RO membrane UVC tolerance, and economic analysis, suggested that UVC RL shows promise for application to bacteria control in seawater RO.