Distribution of Typical Taste and Odor Compounds and Possible Formation of 2,4,6-Trichloroanisole in Drinking Water Treatment Plants
2017
Bai, Xiuzhi | Qu, Zhipeng | Li, Bin | Li, Haipu | Zhang, Ting | Yang, Zhaoguang
Distribution of ten taste and odor (T&O) compounds were investigated in 135 finished water samples from 43 drinking water treatment plants (DWTPs). 2-Methylisoborneol (MIB), geosmin, and 2,4,6-trichloroanisole (2,4,6-TCA) were detected in 53.4, 41.5, and 14.1% of the samples, respectively. The corresponding concentrations were in the range of 18.0–53.1 ng L⁻¹ for MIB, 4.2–6.4 ng L⁻¹ for geosmin, and 0.5–6.6 ng L⁻¹ for 2,4,6-TCA. The other seven T&O compounds, β-ionone, 2,3,6-trichloroanisole (2,3,6-TCA), 2,3,4-trichloroanisole (2,3,4-TCA), 2,4,6-tribromoanisole (2,4,6-TBA), 2-isobutyl-3-methoxypyrazine (IBMP), 2-isopropyl-3-methoxypyrazine (IPMP), and trans-2,cis-6-nonadienal (NDE) were never found in all samples. The results from finished water of DWTPs compared with associated reservoirs indicated that 2,4,6-TCA was formed in the water treatment processes. To determine the chemical formation of 2,4,6-TCA by chlorination, the concentrations of different chloroanisoles in anisole-containing water at pH 5.5–9.0 and 25 °C were measured. The results from chlorination showed that only 2-chloroanisole (2-CA), 4-chloroanisole (4-CA), and 2,4-dichloroanisole (2,4-DCA) could be detected. Their formation rates were all below 3.3% at each pH value, but the reaction was more active at pH 5.5 because of acid catalyzed effect. Accordingly, the chemical formation of 2,4,6-TCA by chlorination was not confirmed in this study, which suggested that the formation of 2,4,6-TCA was related to the methylation of 2,4,6-trichlorophenol with fungi. These findings increase our understanding on the formation of 2,4,6-TCA and provide insights into managing and controlling T&O problems in drinking water.
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