Korea Institute of Science and Technology, Sŏul, Seoul, South Korea

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Publications (4)6.6 Total impact

  • Dongjin Kim · Doo-Il Kim · Jae-Hong Kim · Thorsten Stoesser ·
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    ABSTRACT: Three-dimensional numerical analyses of flow and transport characteristics in two representative multichamber ozone contactor models with different chamber width were conducted using large eddy simulation (LES). Both time-averaged and instantaneous flow patterns suggest that the flow is characterized by the occurrence of large turbulent structures leading to extensive short-circuiting between chambers and internal recirculation inside the chambers. The flow is also found to be highly three-dimensional, as secondary vortices and recirculation zones develop. The simulation results further suggest that the hydrodynamics in ozone contactors can be improved by reducing the chamber width. The results of the LES are qualitatively verified using previously reported tracer test results obtained from laboratory experiments. The LES technique, applied to the ozone contactor flow and transport of a tracer for the first time, is expected to serve as a powerful tool for existing reactor flow diagnosis, reactor retrofitting as well as for new reactor design.
    Journal of Environmental Engineering 01/2010; 136(1). DOI:10.1061/(ASCE)EE.1943-7870.0000118 · 1.27 Impact Factor
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    ABSTRACT: The David L. Tippin Water Treatment Facility in Tampa, Fla., treats Hillsborough River water, which has relatively high organic matter content, especially during high-rainfall seasons. In 2001, ozonation and biologically activated carbon (BAC) filtration were implemented along with a few additional modifications to the existing conventional process. After the start of the new process, unexpectedly low monochloramine formation efficiency and rapid decay of monochloramine residual in treated waters were observed. By changing the sequence of free chlorine and ammonia injection and by providing sufficient mixing and reaction time for free chlorine, monochloramine formation efficiency was dramatically increased. Among several factors that might affect monochloramine decay rate, the particulate matter produced from the BAC filters, presumably because of microbial activities, was found to be primarily responsible for the monochloramine demand. The filter backwashing practice was modified to successfully enhance filter performance and stabilize monochloramine in treated waters.
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    ABSTRACT: While the reactivity of C60 has been described in a variety of organic solvents, little information is available regarding aqueous-based reactions due to solubility limitations. In this study, a reaction between C60, as a nanoscale suspension, and dissolved ozone in the aqueous phase was investigated. Findings indicate a facile reaction occurs, resulting in aggregate dissolution concurrent with formation of water-soluble fullerene oxide species. Product analyses, including 13C NMR, MS (LDI), FTIR, UV-Vis, and XPS, indicate highly oxidized fullerene with an average of approximately 29 oxygen additions per molecule, arranged in repeating hydroxyl and hemiketal functionalities. These findings are significant in that they (1) demonstrate the feasibility of other aqueous-based fullerene chemistries, including those for alternative synthesis routes, which might otherwise be considered prohibitive on the basis of solubility limitations, and (2) imply that the aqueous reactivity of fullerene-based materials must be considered appropriately for accurate assessment of their transport, fate, and potential risk(s) in environmental systems.
    Environmental Science and Technology 12/2007; 41(21):7497-502. DOI:10.1021/es0708058 · 5.33 Impact Factor
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    ABSTRACT: This article introduces ozone contactor model (OCM) software developed for full-scale ozone bubble-diffuser contactor design and optimization. OCM software can be used by utilities to optimize reactor design and operation and to demonstrate compliance with regulations regarding pathogen and bromate control in drinking water. The software developed in this study simulates full-scale ozone bubble-diffuser contactor performance for drinking water treatment. The OCM software can be used by engineers for designing ozone disinfection systems, by plant operators for system operation optimization and regulatory compliance demonstration, and by government officials for drinking water regulations development. The OCM software was designed to be user-friendly with graphical user interfaces so users can perform complex simulations under various design and operating scenarios without extensive training. This article also suggests that model simulation is a promising tool for plant design and optimization, possibly beyond the ozone disinfection processes presented.