An Integrated Design Approach For Improving Drinking Water Ozone Disinfection Treatment Based On Computational Fluid Dynamics

Ozonation is currently considered as one of the most effective microbial disinfection technologies due to its powerful disinfection capacity and reduction in levels of chlorinated disinfection by-products (DBP). However, ozonation of waters containing bromide can produce bromate ion above regulated levels, leading to tradeoffs between microbial and chemical risks. In efforts to meet increasingly stringent drinking water regulations and to be cost-effective, water suppliers are required to optimize ozone dosage. Therefore, there is a need to develop a robust and flexible tool to accurately describe ozone disinfection processes and contribute to their design and operation. Computational fluid dynamics (CFD) has come into use recently for evaluating disinfection systems. However, the focus of its application has been largely on modelling the hydraulic behaviour of contactors, which is only one component of system design. The significance of this dissertation is that a fully comprehensive three dimensional (3D) multiphase CFD model has been developed to address all the major components of ozone disinfection processes: contactor hydraulics, ozone mass transfer, ozone decay, and microbial inactivation. The model was validated using full-scale experimental data, including tracer test results and ozone profiles from full-scale ozone contactors in two Canadian drinking water treatment plants (WTPs): the DesBaillets WTP in Montral, Quebec and the Mannheim WTP in Kitchener, Ontario. Good agreement was observed between the numerical simulation and experimental data. The CFD model was applied to investigate ozone contactor performance at the DesBaillets WTP. The CFD-predicted flow fields showed that recirculation zones and short circuiting existed in the DesBaillets contactors. The simulation results suggested that additional baffles could be installed to increase the residence time and improve disinfection efficiency. The CFD model was also used to simulate ozone contactor perf.