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OZONE CONTACTOR FLOW VISUALIZATION AND CHARACTERIZATION USING 3-DIMENSIONAL LASER INDUCED FLUORESCENCE
Citation:
KIM, D., P. J. ROBERTS, M. ELOVITZ, AND J. KIM. OZONE CONTACTOR FLOW VISUALIZATION AND CHARACTERIZATION USING 3-DIMENSIONAL LASER INDUCED FLUORESCENCE. Presented at WQTC MEETING, CHARLOTTE, NC, November 04 - 08, 2007.
Description:
Hydrodynamics of ozone contactors have a crucial impact on efficient inactivation of pathogens such as Cryptosporidium as well as control of disinfection byproducts such as bromate. Improper mixing behaviors including short-circuiting, internal recirculation and presence of stagnant zones in ozone contactors have been predicted by computer simulations but few studies have provided direct experimental evidence. In this study, we used 3-dimensional laser induced fluorescence (3D-LIF) technique to experimentally visualize mixing behaviors in a lab-scale model ozone contactor by quantifying at very high resolution the entire instantaneous tracer concentration over a sampling space in real time. Briefly, a laser light is swept into the reactor in a 2-dimensional plane using a high-speed oscillating mirror. The laser causes the dye to fluoresce and the emitted light is captured by a synchronized high-sensitivity CCD camera orientated perpendicular to the plane. A second mirror then moves the laser plane horizontally a short distance and the process is repeated. Three-dimensional images of the fluorescence emission is thereby captured in real time and later analyzed to obtain quantitative tracer concentration fields as a function of time. Using a model reactor studied, we demonstrate that short-circuiting and internal recirculation are highly likely in multi-chambered design, which are most widely used for disinfection processes. We present suggestions for design and operation optimization to reduce the back-mixing and increase the overall treatment efficiency. This study demonstrates that this technique might serve as a highly innovative and very useful tool for flow optimization and ultimately for process design.