Journal:  Water Research

Author: Darryl B. Jones, Hocheol Song, Tanju Karanfil

Abstract:

In this study, the impacts of three preoxidation strategies [i.e., using potassium permanganate (KMnO₄), chlorine dioxide (ClO₂), or hydrogen peroxide (H₂O₂)] before preformed monochloramine (NH₂Cl) addition on the formation and speciation of iodinated trihalomethanes (I-THMs) were evaluated at the Br⁻/I⁻ mass ratio of 10 in two natural waters. The effects of preoxidant dose, Br⁻/DOC, and I⁻/DOC ratio were investigated. Preoxidation with KMnO₄ increased I-THM formation due to an increase in iodoform (CHI₃) and brominated I-THM (CHBrClI, CHBrI₂, CHBr₂I) formation. In contrast, preoxidation with ClO₂ sometimes reduced I-THM formation, primarily due to a reduction in CHI₃ formation. Preoxidation with H₂O₂ had no effect on I-THM formation or speciation. I-THM formation from each preoxidant alone was considerably less than the formation from NH₂Cl. Overall, preoxidant type, preoxidant/DOC, preoxidant/I⁻, and I⁻/DOC ratios are the important factors that water utilities should evaluate when assessing the impact of preoxidation for controlling I-THM formation.

Keywords: I-THM, THM, Bromide, Iodide, NOM, Preoxidation, Potassium permanganate, Chlorine dioxide, Hydrogen peroxide, Monochloramine

DOI: https://doi.org/10.1016/j.watres.2012.07.018