A Simple and Practical Method for Fluence Determination in Bench-Scale UV-LED Setups

In UV disinfection of water, the fluence of UV required to inactivate a target microorganism is determined based on the procedures developed for conventional mercury-based UV lamps with collimation. In this regard, a simple and practical method with a mathematical model and radiometry is proposed for determining the fluence rate with UV light-emitting diodes (UV-LEDs). This method was applied to a bench-scale UV-LED setup and validated by comparing the calculations with the measurements using either a spectroradiometer or a chemical actinometer. The results showed high accordance with spectroradiometer outputs with a linear regression equation y = 0.997x (x: model calculation, y: spectroradiometer output, r² = 0.999, P < 0.001 for n = 20) in an experiment varying the distance between the measurement points and the UV-LEDs. Meanwhile, the proposed method and chemical actinometry exhibited 98% concordance. Furthermore, this method was applied to determine the fluence-response profiles of Pseudomonas aeruginosa, and the results demonstrated that the proposed method was appropriate at two different distances between the UV-LEDs and the solutions. To conclude, the proposed method can determine the fluence in a UV-LED bench-scale setup in a simple and practical way, which would potentially promote the research and development of water treatment using UV-LEDs.