• Journal of Korean Society of Environmental Engineers
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• v.31 no.2
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• pp.125-131
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• 2009

Reductive dechlorination of polychlorinated dibenzo-p-dioxins (PCDDs) and its toxicity change were predicted by the linear free energy relationship (LFER) model to assess the zero-valent iron (ZVI) and anaerobic dechlorinating bacteria (ADB) as electron donors in PCDDs dechlorination. Reductive dechlorination of PCDDs involves 256 reactions linking 76 congeners with highly variable toxicities, so is challenging to assess the overall effect of this process on the environmental impact of PCDD contamination. The Gibbs free energies of PCDDs in aqueous solution were updated to density functional theory (DFT) calculation level from thermodynamic results of literatures. All of dechlorination kinetics of PCDDs was evaluated from the linear correlation between the experimental dechlorination kinetics of PCDDs and the calculated thermodynamics of PCDDs. As a result, it was predicted that over 100 years would be taken for the complete dechlorination of octachlorinated dibenzo-p-dioxin (OCDD) to non-chlorinated compound (dibenzo-p-dioxin, DD), and the toxic equivalent quantity (TEQ) of PCDDs could increase to 10 times larger from initial TEQ with the dechlorination process. The results imply that the single reductive dechlorination using ZVI or ADB is not suitable for the treatment strategy of PCDDs contaminated soil, sediment and fly ash. This LFER approach is applicable for the prediction of dechlorination process for organohalogen compounds and for the assessment of electron donating system for treatment strategies.

• Analytical Science and Technology
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• v.12 no.1
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• pp.61-67
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• 1999

Two of municipal waste incinerators were selected as surveying facilities to research on the emission of dioxin and precusors. The sampling of flue gas and analysis was performed in the selected facilities. From the result, the emission patterns of dioxin and precusors, their relatership were examined. The toxic equivalency quantity(TEQ) of dioxin concentration was evaluated in two municipal waste incinerators. The 76.24% and 60.84% of total dioxin concentration in A and B incinerator were made up of the penta-, hexa- and hepta-chlorinated dibenzo-p-dioxin, respectively. Therefore, to reduce the dioxins in flue gas have to control the formation of furans. The chlorobenzenes and chlorophenols were analyzed in two incinerators. The 1,2,4,5-tetrachlorobenzene, penta-, and hexachlorobenzene are discharged and 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol are discharged mainly in A and B municipal waste incinerators.