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    Iodate and Iodo-Trihalomethane Formation during Chlorination of Iodide-Containing Waters: Role of Bromide

    Access Status
    Fulltext not available
    Authors
    Criquet, Justine
    Allard, Sebastien
    Salhi, E.
    Joll, Cynthia
    Heitz, Anna
    Von Gunten, Urs
    Date
    2012
    Type
    Journal Article
    
    Metadata
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    Citation
    Criquet, Justine and Allard, Sebastien and Salhi, Elisabeth and Joll, Cynthia and Heitz, Anna and von Gunten, Urs. 2012. Iodate and Iodo-Trihalomethane Formation during Chlorination of Iodide-Containing Waters: Role of Bromide. Environmental Science & Technology. 46: pp. 7350-7357.
    Source Title
    Environmental Science & Technology
    DOI
    10.1021/es301301g
    ISSN
    0013-936X
    URI
    http://hdl.handle.net/20.500.11937/3439
    Collection
    • Curtin Research Publications
    Abstract

    The kinetics of iodate formation is a critical factor in mitigation of the formation of potentially toxic and off flavor causing iodoorganic compounds during chlorination. This study demonstrates that the formation of bromine through the oxidation of bromide by chlorine significantly enhances the oxidation of iodide to iodate in a bromide-catalyzed process. The pH-dependent kinetics revealed species specific rate constants of k(HOBr + IO-) = 1.9 × 106 M-1 s-1, k(BrO- + IO-) = 1.8 × 103 M-1 s-1, and k(HOBr + HOI) < 1 M-1 s-1. The kinetics and the yield of iodate formation in natural waters depend mainly on the naturally occurring bromide and the type and concentration of dissolved organic matter (DOM). The process of free chlorine exposure followed by ammonia addition revealed that the formation of iodo-trihalomethanes (I-THMs), especially iodoform, was greatly reduced by an increase of free chlorine exposure and an increase of the Br-/I- ratio. In water from the Great Southern River (with a bromide concentration of 200 µg/L), the relative I-incorporation in I-THMs decreased from 18 to 2% when the free chlorine contact time was increased from 2 to 20 min (chlorine dose of 1 mg Cl2/L).This observation is inversely correlated with the conversion of iodide to iodate, which increased from 10 to nearly 90%. Increasing bromide concentration also increased the conversion of iodide to iodate: from 45 to nearly 90% with a bromide concentration of 40 and 200 µg/L, respectively, and a prechlorination time of 20 min, while the I-incorporation in I-THMs decreased from 10 to 2%.

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    • Influence of bromide on iodate and iodo-trihalomethane formation during chlorination of iodide-containing waters
      Criquet, J.; Allard, Sebastian; Salhi, E.; Joll, C.; Von Gunten, Urs; Heitz, A. (2012)
      The kinetics of iodate formation during chlorination of iodide-containing waters is a key factor in the formation of iodoorganic compounds. In contrast to bromate, iodate is considered to be non-toxic. A strategy to reduce ...
    • Impact of bromide and iodide during drinking water disinfection and potential treatment processes for their removal or mitigation
      Gruchlik, Yolanta; Tan, J; Allard, Sebastian; Heitz, Anna; Bowman, M.; Halliwell, D.; Gunten, U.; Criquet, Justine; Joll, Cynthia (2014)
      In this study, the impact of bromide and iodide on disinfected waters was examined and potential treatment technologies for their removal or mitigation were investigated. Distributed waters from two Western Australian ...
    • Toxicity evaluation of synthetic waters based on Br-Cl-I-THMs formation during the chlorine/ammonia process
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      Monochloramine (NH2Cl) is commonly used as an alternative to chlorine for disinfection because it is less reactive with the organic matrix, therefore forms less regulated DBPs and leads to a more stable residual. However, ...
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