Ultraviolet light-emitting diode (UV-LED) water disinfection photoreactors: A review

Water disinfection is a crucial pillar in the water treatment process. Ultraviolet (UV) irradiation is increasingly being recognized as a potent method devoid of chemicals and effective against a spectrum of pathogens. While conventional UV lamps dominate the market, promising alternatives exist, such as excimer lamps, microplasma lamps, and UV light-emitting diodes (UV-LEDs). UV-LEDs have notable advantages due to their sturdy construction, absence of mercury vapor, adaptable wavelengths, immediate operation, pulsating capabilities, compactness, and enduring lifespans. Designing an optimal UV-LED reactor requires meticulous attention to be paid to several key factors. These factors include kinetics, hydrodynamics, radiation, cooling techniques, fouling prevention, serviceability, and safety protocols. This article presents a thorough exploration of recent breakthroughs and profound insights related to UV-LED water disinfection systems, providing guiding principles for future advancements. The phenomena central to UV-LED water disinfection systems, including microbial inactivation kinetics, radiation dispersion aided by lenses and reflectors, and the dynamics of flow regimes, are first explored. Subsequently, the considerations of implementing UV-LED water disinfection system designs are presented in detail, exemplified by discussions on UV-LED thermal management. The crucial aspects of evaluating the performance of UV-LED water disinfection systems are then highlighted, with a focus on delivered UV doses and reactor efficiency parameters.