The 9th International Conference on Water Resource and Environment (WRE 2023)

Abstract: Ultraviolet (UV) light-emitting diode (UV-LED) has been regarded as an emerging UV light source for disinfection and photochemical oxidation in water and wastewater treatment. The performance of a UV reactor depends on the UV fluence (or UV dose). The combination of a spatial photon fluence rate (PFR) distribution (i.e., Optical field) and computational fluid dynamics is necessary to obtain the UV fluence of a UV reactor, as well as the configuration of a UV reactor for optimal efficiency (e.g., increase the reflection of the reactor inner-wall). Therefore, an accurate quantification of the spatial PFR distribution is significant. However, this work has not been well studied for UV-LED reactor.
As compared to the conventional low-pressure (LP) mercury lamp, UV-LED has the merits of small size and various output wavelengths, which allow for more flexible light source layout and wavelength selection in the design of a reactor. A micro-fluorescent silica detector (MFSD, 0.7 mm³ volume) can capture photons uniformly from nearly all directions at a test point. This MFSD, fixed on a precise two-dimensional guideway, could directly measure the PFR distributions accurately in various types of UV reactors, such as LP reactor, medium-pressure UV lamp reactor, reactor with different inner-wall materials, and reactors with multiple lamps, exhibiting high stability, fast response, water resistance, and small size. This detector has great potential to be applied for the determination of optical field for UV-LED reactors.
So we herein report the use of this MFSD to reveal the optical fields of commercial UV-LED reactors. At first, the PFR distribution of a single UV-LED chip was measured in the air, which not only validated the PFR distribution model of UV-LED, but also measured the output power of a single UV-LED chip. Then, the PFR distribution of a UV-LED reactor filled with water with various UV transmittances were measured. The impact of water UVT and inner wall reflection were examined. This work provides significant results for the optimal design and high-efficacy operation of a UV reactor.