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INTRODUCTION
Quality aspects become the primary concern for drinking water treatment when water quantity problems have been solved (Bruchet & Duguet 2004). The key issues in drinking water treatment are not only the removal of toxic pollutants, but also the removal of odorants (Tobien et al. 2000). Thus, the treatment and control of odor have increased in priority because odorants have long been related to the quality and safety of drinking water (Antonopoulou et al. 2014). Several classes of compounds have been reported to be responsible for odor: for example, sulfides, dicyclopentadiene and analogues, and disinfection byproducts (DBPs) to name a few (Park et al. 2007). However, it is a challenging task to target such low levels of specific compounds in a complex mixture which contains extremely low concentrations, usually in the range of ng L−1 (Park et al. 2007; Persson et al. 2007; Srinivasan & Sorial 2011; Watanabe et al. 2014). Few approaches have been identified to be efficient in odor removal, including the use of activated carbon (both powdered activated carbon (PAC) and granular activated carbon (GAC)) and alum coagulation/sand filtration (Cook et al. 2001; Jung et al. 2004; Sattler & Rosenberk 2006; He et al. 2016). However, adsorption capacity is vulnerable to the existence of natural organic matter, and additional costs must be paid for regeneration of activated carbon (Bansal et al. 2005).
Fortunately, the use of oxidants (chlorine, chlorine dioxide, potassium permanganate (KMnO4), ozone (O3), etc.) has been proved to be an alternate approach for odor removal, even though it is ineffective in removing geosmin and 2-methylisoborneol because of the resistance of tertiary alcohols towards oxidants (Antonopoulou et al. 2014; Zhang et al. 2015). Nevertheless, chlorinated DBPs and associated odor compounds inhibited further application of both chlorine and chlorine dioxide (Srinivasan & Sorial 2011).
Previous studies have demonstrated that both KMnO4 and O3 perform well for odor removal in drinking water treatment processes (Lalezary et al. 1986; Jung et al. 2004) as strong oxidants. The outstanding advantages of KMnO4 and O3 for odor removal in drinking water lie in their strongly oxidative ability and great compatibility with conventional treatment processes such as coagulation and flocculation, as well as the excellent adsorption and catalytic capacity of the hydrated manganese dioxide (HMD) formed...