Ozonation of iodide-containing waters: Selective oxidation of iodide to iodate with simultaneous minimization of bromate and I-THMs.

Allard, S. and Nottle, C.E. and Chan, A. and Joll, C. and von Gunten, U. 2013. Ozonation of iodide-containing waters: Selective oxidation of iodide to iodate with simultaneous minimization of bromate and I-THMs. Water Research. 47 (6): pp. 1953-1960.

Source Title

Water Research

DOI

10.1016/j.watres.2012.12.002

ISSN

0043-1354

Remarks

NOTICE: this is the author’s version of a work that was accepted for publication in Water Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Water Research, Vol. 47, no. 6, 2013.

URI

http://hdl.handle.net/20.500.11937/4522

Collection

Curtin Research Publications

Abstract

The presence of iodinated disinfection by-products (I-DBPs) in drinking water poses a potential health concern since it has been shown that I-DBPs are generally more genotoxic and cytotoxic than their chlorinated and brominated analogs. I-DBPs are formed during oxidation/disinfection of iodide-containing waters by reaction of the transient hypoiodous acid (HOI) with natural organic matter (NOM). In this study, we demonstrate that ozone pre-treatment selectively oxidizes iodide to iodate and avoids the formation of I-DBPs. Iodate is non-toxic and is therefore a desired sink of iodine in drinking water. Complete conversion of iodide to iodate while minimizing the bromate formation to below the guideline value of 10 μg L−1 was achieved for a wide range of ozone doses in five raw waters with DOC and bromide concentrations of 1.1–20 mg L−1 and 170–940 μg L−1, respectively. Lowering the pH effectively further reduced bromate formation but had no impact on the extent of iodate and bromoform formation (the main trihalomethane (THM) formed during ozonation). Experiments carried out with pre-chlorinated/post-clarified samples already containing I-DBPs, showed that ozonation effectively oxidized I-THMs. Therefore, in iodide-containing waters, in which I-DBPs can be produced upon chlorination or especially chloramination, a pre-ozonation step to oxidize iodide to iodate is an efficient process to mitigate I-DBP formation.