| Summary: | 碩士 === 逢甲大學 === 環境工程與科學所 === 91 === Chlorine dioxide is getting attractive as being an alternative disinfectant in drinking water treatment worldwide. This study is focused on the oxidation of humic acids by chlorine dioxide and the formation of inorganic disinfection by-products in aqueous environment. The parameters used in this research include pH, dosage of chorine dioxide, and concentrations of humic acids and bromide ions.
The result indicates that the pH values in aqueous phase would affect the decomposition pathway of chlorine dioxide in pure water. Inorganic by-products generated from chlorine dioxide tend to form chloride ion under acid condition and form chlorite ion under alkaline condition. Chlorine dioxide could decrease UV254 for 25% and remove THMFP for 14% while the ratio of chlorine dioxide dosage to DOC is set at 2.5. Furthermore, the decomposition of chlorine dioxide is catalyzed by humic acids to dramatically enhance the formation of inorganic by-products per chlorine dioxide dose from 20~30% (in pure water) to 80~95%. If bromide ions are added simultaneously in aqueous solution, bromide ions could be oxidized by either chlorine dioxide itself or hypochlorous acids (HOCl/OCl-), which are derived during the course of chlorine dioxide decomposition. However, bromide could not be oxidized into becoming bromate ions. Although DOC and UV254 of humic acids would not be influenced upon reaction with chlorine dioxide with the presence of bromide ions, the precursors of producing THMs has been found to be further suppressed. On the contrary, the formation potential of HAAs increases due to the addition of bromide ions participating in chlorination of organics.
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