No abstract

Broadly applicable disinfection by-product (DBP) precursor surrogate parameters could be leveraged at drinking water treatment plants (DWTPs) to curb formation of regulated DBPs, such as trihalomethanes (THMs). In this study, dissolved organic carbon (DOC), ultraviolet absorbance at 254 nm (UV 254 ), fluorescence excitation/emission wavelength pairs (I Ex/Em ), and the maximum fluorescence intensities (F MAX ) of components from parallel factor (PARAFAC) analysis were evaluated as total THM formation potential (TTHMFP) precursor surrogate parameters. A diverse set of source waters from eleven DWTPs located within watersheds underlain by six different soil orders were coagulated with alum at pH 6, 7, and 8, resulting in 44 sample waters. DOC, UV 254 , I Ex/Em , and F MAX values were measured to characterize dissolved organic matter in raw and treated waters and THMs were quantified following formation potential tests with free chlorine. For the 44 sample waters, the linear TTHMFP correlation with UV 254 was stronger (r 2 = 0.89) than I 240/562 (r 2 = 0.81, the strongest surrogate parameter from excitation/emission matrix pair picking), F MAX from a humic/fulvic acidlike PARAFAC component (r 2 = 0.78), and DOC (r 2 = 0.75). Results indicate that UV 254 was the most accurate TTHMFP precursor surrogate parameter assessed for a diverse group of raw and alum-coagulated waters.

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Although disinfection byproducts (DBPs) were discovered decades ago and surrogate parameters have been developed to track their precursors, the accuracy of these metrics in waters impacted by heavy rainfall events is largely unknown. We measured DBPs and their precursor surrogate parameters in a water body impacted by 28 cm of rain between 4/24/11 and 4/26/11. Raw waters collected from four locations within the water body from April to August 2011 were treated by coagulation and anion exchange. Ultraviolet absorbance at 254 nm (UV 254 ) and fluorescence excitation-emission pairs (I Ex/Em ) were measured. Excitation-emission matrices (EEMs) were processed with parallel factor (PARAFAC) analysis, which resulted in six component fluorophore groups (C1-C6), each with a maximum intensity (F MAX ). DBP formation potential (DBPFP) with free chlorine was used to assess the precursor concentrations. Chloroform (TCM) was the predominant DBP formed, and 37-63% of its precursors were removed by treatment. The trichloromethane formation potential (TCMFP)-UV 254 correlation was poor (r 2 ¼ 0.25) and adversely impacted by the influx of dissolved iron from the heavy rainfall event; in contrast, correlations with fluorescencebased metrics were strong -TCMFP-I 278/506 (r 2 ¼ 0.88) and TCMFP-C1 F MAX (r 2 ¼ 0.87) -illustrating the accuracy of these precursor surrogate parameters in waters impacted by a heavy rainfall event.

E105Granderson et al | http://dx. E107Granderson et al | http://dx.