Characterization of cylindrical UV-LED water disinfection photoreactors with reflective surfaces: Model development and validation

In response to the increasing demand for sustainable water treatment, this study investigates the performance of ultraviolet light-emitting diode (UV-LED) reactors at realistic household flow rates. A custom U-shaped cylindrical reactor was designed specifically for high practical flow rates, a configuration explored for the first time in point-of-use applications. The reactor's disinfection efficiency was evaluated, demonstrating the feasibility of UVLEDs as an eco-friendly alternative to conventional mercury lamps. Additionally, a novel radiation model was developed to accurately simulate complex optical interactions, including absorption within quartz components and reflection dynamics within the reactor. Comprehensive computational fluid dynamics simulations, utilizing both Eulerian and Lagrangian approaches, were conducted alongside experimental assessments using Escherichia coli ATCC 8739. Flow rates were varied from 1 to 7 l per minute (LPM). Results demonstrated that optimizing key optical parameters, such as UV transmittance and LED viewing angle, enhances microbial inactivation. Specifically, increasing the LED viewing angle from 9.5 degrees to 38 degrees boosted disinfection by 28 %, while an 18 % decrease in UV transmittance reduced microbial inactivation by 1.1 log units. These findings underscore the potential of optimized UV-LED reactor designs for effective and energy-efficient point-of-use water purification at householdrelevant flow rates.