a b s t r a c tOzonation is known to be very effective in the removal of odorants from source water. However, it is not known if ozonation is effective in the removal of multiple odorants causing different types of odors. In this study, the removal performance for odors and odorants were evaluated in a Water Treatment Plant (WTP), which was equipped with coagulation, sedimentation, ozonation, biological activated carbon (BAC) filtration, sand filtration, and chlorination in succession and located in the downstream of the Huangpu (HP) River, over the period from April, 2014 to April, 2015. Flavor profile analysis (FPA) results showed that the source water was constantly associated with septic and musty odors. Geosmin and 2-MIB, with an average OAV of 4.54 and 1.38, respectively, were the major odorants for musty odor, while bis(2-chloroisopropyl) ether, DEDS and DMDS with an average OAV of 2.35, 1.65 and 0.78, respectively, might be responsible for the septic odor. While the musty odor could be removed effectively through the combination of ozonation and BAC, the septic odor and associated odorants required further treatment with sand filtration and chlorination for complete removal. It is clear that the advanced treatment process was effective for the treatment of source water containing complicated odorants. It should be noted that the sedimentation process needs careful management because release of odorants may occur during the treatment. The result of this study will be helpful for the mitigation of odors in WTP using source waters suffering from complicated odor problems.

Odor problems in drinking water, particularly swampy/septic odors, are normally triggered by a set of organic compounds with odor threshold concentrations (OTC) ranging from ng L À1 to mg L À1. With such a low level of OTC, it has long been a challenge to effectively determine the odor-causing compounds in highly complex samples. The Huangpu and Huai rivers, as source waters in south China, have exhibited continuous swampy/septic odor over the entire year, yet the corresponding odor-causing compounds remain unclear. In order to screen the odor-causing compounds in these two rivers, a method to simultaneously determine fifty-four frequently encountered compounds with categories of thioethers, aldehydes, pyrazines, benzenes and phenols, has been developed using comprehensive twodimensional gas chromatography with time-of-flight mass spectrometry (GC Â GC-TOFMS) based on liquid-liquid extraction. The results indicated that this method could allow the analysis of different categories of compounds without derivatization at considerably higher sensitivities. Four thioether compounds, including dimethyl disulfide, diethyl disulfide, propyl sulfide, and amyl sulfide, and one ether compound (bis(2-chloroisopropyl) ether) were at least detected in one of the source waters with a concentration higher than their OTC value, suggesting that these compounds might be the main compounds causing the swampy/septic odor. At the same time, other compounds, including pyrazine, pyridine, 2-methyl-phenol, 2-nitro-phenol, and 2,6-dimethyl-phenol, were detected with a concentration lower than their respective OTC value. The contribution of these compounds to the swampy/septic odor requires further evaluation.

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