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UBC Theses and Dissertations

Developmemt of UV photoreactor models for water treatment Elyasi, Siamak


Ultraviolet (UV) reactors are promising for the future of drinking water and wastewater treatment technology. Models simulating the performance of UV reactors enhance our understanding of the fundamental principles governing the operation of these units. When modeling the performance of UV reactors, governing equations for all related phenomena are derived and solved. The theoretical models and experimental approaches for evaluating the results of these models are comprehensively reviewed and presented in this research. The thesis presents a step-by-step methodology for solving the governing equations of UV reactors. This research presents a general method that integrates the Fresnell, Snell, and Beer-Lambert laws for modeling the radiant distribution in a medium. The model uses the boundary conditions to realistically simulate the fluence/irradiance rate around the radiant source, in particular, in the zone closest to the radiant source. Different low-pressure UV lamps were tested under different operating conditions using photodiodes and a radiometer. The experimentally measured irradiance rate is in excellent agreement with the results of the simulation. Conventionally, the performance of a UV reactor is evaluated using the concentration of photoreactive chemicals at the outlet vs. the inlet. This research presents a novel method for measuring the concentration distribution of a photoreactive chemical inside a photoreactor using a modified planar laser-induced fluorescence method. The fluence distribution was measured for a pilot scale photoreactor under different operating conditions. The visualized result of the fluence distribution revealed significant information about the local/overall performance of the photoreactor. This method is a powerful diagnostic tool for the determination of the local performance inside a UV reactor, as well as for the evaluation of models simulating UV reactor behavior. A computational fluid dynamic (CFD) model was developed in order to simulate UV photoreactors in the Eulerian framework for microbial disinfection and chemical removal using a UV-based hydroxyl radical initiated oxidation process. The integrated CFD model of UV photoreactor performance was successfully validated by comparisons with experimental results. This verified procedure can be applied to the simulation and optimization of UV photoreactors with different geometries and operating conditions.

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