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UBC Theses and Dissertations

Study of the inactivation of microorganisms using UV-LEDs Kheyrandish, Ataollah


Application of ultraviolet (UV) radiation for water treatment has been increasing steadily in the past two decades. Further, significant improvements in semiconductor technology have made ultraviolet light emitting diodes (UV-LEDs) a viable alternative to conventional UV sources for water treatment. However, utilizing UV-LEDs for water disinfection comes with challenges related to their radiation measurements due to their specific structure, operation, and radiation pattern. Without a standardized measurement method, the efficacy of this new radiation source on the inactivation of waterborne microorganisms could not be determined accurately. In this study, in order to determine the fluence delivered to a microorganism’s solution, first, a method was developed to properly operate, control, and measure the output of the UV-LEDs. It was found that, not only the operational conditions affect the UV-LEDs output, but also the measurement techniques were critical in obtaining accurate results. Then, the radiation distribution was simulated. The radiation model was validated by two common measurement techniques, chemical actinometry and radiometry. Using the validated model, common radiation modeling presumptions such as the point source assumption and symmetry assumption for radiation profile of UV-LEDs were evaluated. Subsequently the radiation model and the operational method were implemented to develop a protocol for fluence determination of UV-LED systems. In this protocol, the average fluence was estimated by measuring the irradiance at a few points for a collimated and uniform radiation on a petri dish surface containing microorganism solution. Finally, the developed fluence determination protocol was tested in different setups to evaluate the radiation distribution and its effect on microbial inactivation kinetics measurements. A novel setup was presented for UV-LED kinetics studies; further, the inactivation kinetics of a common waterborne microorganism, E. coli, was measured. This study includes a fundamental holistic insight for fluence determination of UV-LED systems. The developed protocols for UV-LED operation and fluence determination studies help researchers to perform reliable UV-LED inactivation studies and obtain precise kinetics data.

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