A review on LED technology in water photodisinfection

The increase in efficiency achieved by UV LED devices has led to a compelling increase in research reports on UV LED water treatment for consumption in the past few years. This paper presents an in-depth review based on recent studies on the suitability and performance of UV LED-driven processes for water disinfection. The effect of different UV wave-lengths and their combinations was analysed for the inactivation of various microorganisms and the inhibition of re-pair mechanisms. Whereas 265 nm UVC LED present a higher DNA damaging potential, 280 nm radiation is reported to repress photoreactivation and dark repair. No synergistic effects have been proved to exist when coupling UVB + UVC whereas sequential UVA-UVC radiation seemed to enhance inactivation. Benefits of pulsed over contin-uous radiation in terms of germicidal effects and energy consumption were also analysed, but with inconclusive re-sults. However, pulsed radiation may be promising for improving thermal management. As a challenge, the use of UV LED sources introduces significant inhomogeneities in the light distribution, pushing for the development of ade-quate simulation methods to ensure that the minimum target dose required for the target microbes is achieved. Con-cerning energy consumption, selecting the optimal wavelength of the UV LED needs a compromise between the quantum efficiency of the process and the electricity-to-photon conversion. The expected development of the UV LED industry in the next few years points to UVC LED as a promising technology for water disinfection at a large scale that could be competitive in the market in the near future.