Examination of disinfection by-product (DBP) formation in source waters: A study using log-transformed differential spectra

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• 作者：Mingquan Yan ; Gregory V. Korshin ; Hyun-Shik Chang
• 关键词：Absorbance ; DBPs ; Dissolved organic matter (DOM) ; Halogenation ; Log-transformation
• 刊名：Water Research
• 出版年：1 March, 2014
• 年：2014
• 卷：50
• 期：Complete
• 页码：179-188
• 全文大小：1935 K

文摘

Formation of disinfection by-products (DBPs) in ten drinking source waters located in the United States was examined in this study. DBP generation was interpreted in the context of halogenation-induced changes of log-transformed absorbance spectra of dissolved organic matter (DOM) present in the waters. This approach allows probing the behavior of relatively minor structures that can be highly sensitive towards any process of interest, notably DOM halogenation. This concept was applied to examine effects of chlorination time on the kinetics of chlorine consumption and release of several DBP groups such as total trihalomethanes (THM₄, including CHCl₃, CHCl₂Br, CHClBr₂ and CHBr₃), haloacetic acids (HAA₉, including MCAA, MBAA, DCAA, TCAA, BCAA, DBAA, BDCAA, DBCAA and TBAA), haloacetonitriles (THAN₄, including TCAN, DCAN, BCAN and DBAN), haloketones (HK₂, including DCP and TCP), chloral hydrate (CH) and chloropicrin (CPN). Two alternative parameters, namely the differential logarithm of DOM absorbance at 350聽nm (DLnA₃₅₀) and change of the spectral slope in the range of wavelengths 325-375聽nm (DSlope_325-375) were introduced to quantify individual DBP species formed and Cl₂ consumption. DLnA₃₅₀ and DSlope_325-375, especially DLnA₃₅₀ were determined to be more reliable than differential absorbance at 272聽nm that was utilized in prior applications of differential spectroscopy to characterize DBP formation. Strong linear relationships between DLnA₃₅₀ values and concentrations of major groups of and individual DBP species (e.g. THM₄, HAA₉, HAN₄ and CPN were found to exist (mostly, R²聽>聽0.95) and the intercept of these correlations with the y-axis was near zero for the examined water sources. Correlations between DLnA₃₅₀ values and concentrations of CH and HK₂ were also strong but they were nonlinear. The slope of the correlations between the concentrations of major groups of DBP species vs -DLnA₃₅₀ were also well correlated with SUVA₂₅₄ and LnA₃₅₀ for all the examined source waters. It indicates that log-transformations of the absorbance spectra of surface water and parameters based on such transformations (e.g., DLnA₃₅₀ and DSlope_325-375) have a potential to provide an alternative reliable approach to monitor the halogenation of DOM and attendant formation of individual DBP species.