The applicability of ozonation to mitigate taste and odor problems in drinking water was investigated. Second-order rate constants of eleven taste and odor compounds with ozone and hydroxyl radicals were determined under laboratory conditions. Measured rate constants for the reaction with hydroxyl radicals are between 3 x 10(9) and 10(10) M(-1)s(-1) and for ozone: kbeta-cyclocitral = 3890 +/- 140 M(-1)s(-1); kgeosmin = 0.10 +/- 0.03 M(-1)s(-1); k3-hexen-1-ol = 5.4 +/- 0.5 x 10(5) M(-1)s(-1); kbeta-ionone = 1.6 +/- 0.13 x 10(5) M(-1)s(-1); k2-isopropyl-3-methoxypyrazine = 50 +/- 3 M(-1)s(-1); k2-methylisoborneol = 0.35 +/- 0.06 M(-1)s(-1); k2,6-nonadienal = 8.7 +/- 0.4 x 10(5) M(-1)s(-1); k1-penten-3-one = 5.9 +/- 0.1 x 10(4) M(-1)s(-1); k2,6-di-tert-butyl-4-methylphenol (BHT) = 7.4 +/- 0.2 x 10(4) M(-1)s(-1); k2,4,6-tribromoanisole = 0.02 +/- 0.01 M(-1)s(-1); k2,4,6-trichloroanisole = 0.06 +/- 0.01 M(-1)s(-1). Experiments conducted in natural waters showed that the removal efficiency during ozonation can be reliably predicted with the determined second-order rate constants. Ozonation is a powerful tool capable of oxidizing most of the taste and odor compounds to more than 50% under typical drinking water treatment conditions. For ozone-resistant taste and odor compounds, the application of advanced oxidation processes may be appropriate.
A taste and odour (T&O) episode in a Swiss town, where consumers complained about a musty odour in their drinking water, was investigated. The application of a combined organoleptic and instrumental method for T&O anaiysis allowed the identification of 2,4,â-trichloroanisole (TCA), with an odour threshold of 30pgl"\ in the drinking water in concentrations of up to 24ngl"''.The absence of this compound in the raw water and after treatment showed that it was formed in the distribution system. Experiments conducted in the iaboratory showed that trichlorophenol as a potential precursor or chlorine as residual disinfectant played a key role in the formation of TCA, which was only formed in the presence of biofiims. Based on these results, appropriate counter-measures, such as water distribution without residual chiorine and maintenance of househoid particie fiiters, are suggested to mitigate this T&O probiem.
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