AWWA ACE65275

The use of ultraviolet-initiated (UV-initiated) advanced oxidation processes (AOP) is rapidlybecoming an attractive alternative for the degradation of harmful organic contaminants that arenot easily removed using conventional water treatment processes. Although UV-initiated AOPsinclude such processes as UV/hydrogen peroxide (H2O2), UV/ozone, and UV/heterogeneouscatalyst (such as titanium dioxide), the focus of this research is the UV/H₂O₂ process with thegoal that the methods and models developed herein can be modified for other UV-initiated AOPprocesses. Design and optimization of UV/H₂O₂ systems must incorporate both reactor design(hydrodynamics, lamp orientation) and chemical kinetics (reaction mechanisms, kinetic rateconstants). While some numerical techniques have been developed for understanding theperformance of these systems, these techniques are limited in their applicability for analyzingfull-scale UV/AOP systems while incorporating both reactor design and chemical kinetics. As aresult, engineers and other water professionals need more appropriate numerical tools to use aspart of the design process and in optimizing UV/AOP systems.The reaction mechanisms for the degradation of organic contaminants by UV-initiated AOPstypically consist of a complex chain of fast chemical reactions. As such, the resultingintermediates and products from these processes will be highly sensitive not only to the lightdistribution within the reactor but also the level of turbulence and micromixing, especially inmixing-limited conditions. In addition, the level of macromixing that is impacted by upstreamand downstream hydraulic configurations, internal reactor layout, and lamp arrangement willinfluence process performance.Researchers have previously demonstrated the importance of combining UV reactor hydraulicswith dynamic fluence rate models to predict the effectiveness of the disinfection process. Arecent AwwaRF study that successfully applied UV-initiated advanced oxidation for thedegradation of organic contaminants recognized the dependence on non-ideal reactorcharacteristics (hydrodynamics and fluence rate) for the overall AOP performance (Linden, etal., 2004). Sharpless and Linden (2003) concluded that development of a predictive UV/AOPmodel that incorporates reactor hydraulics would allow design simulations that optimize lampplacement, minimize light screening, and improve prediction of contaminant removal in differentUV reactors. The research presents the protocol for using CFD models tosimulate UV-initiated AOPs by combining reactor hydraulics, fluence rate distribution, and chemical kinetics. As oxidation pathways for emerging water contaminants are identified, asimulation model, such as the one described, will become an important technique for theevaluation, design, and optimization of advanced oxidation systems. Includes 39 references, figures.

Product Details

Edition:

Vol. - No.

Published:

06/01/2007

Number of Pages:

40

File Size:

1 file , 1.1 MB