Combined use of resin fractionation and high performance size exclusion chromatography for characterization of natural organic matter.

The number and complexity of natural organic matter (NOM) species limits identification of individual NOM compounds. The objective of this study was to employ several characterization techniques (resin fractionation, high performance size exclusion chromatography (HPSEC), and strategic UV254 absorbance) to samples from seven surface water sites in North America, and overcome the shortfalls of each tool. Resin fractionation indicated the samples were all high in hydrophobic acids (HOA), hydrophilic neutrals (HIN) and hydrophilic acids (HIA). Site B was the only site where HIAs were the highest NOM contributors. In the HPSEC analysis, each fraction exhibited a particular molecular weight (MW) range: 100-300 Da (HIN), 1-2 kDa (HOA), and the HIA fractions exhibited MWs between these two ranges. Strategic UV254 measurements were taken at two sites to supplement the HPSEC results, and determine the difference in UV absorbance per unit dissolved organic carbon (SUVA value). Most fractions showed SUVA values of approximately 5 L/mg-m; however, the hydrophilic bases and hydrophobic neutral fractions could not be accurately evaluated due to the very low DOC concentrations for these two fractions (< 0.2 mg/L). These methods are complimentary NOM characterization techniques, and the combined methodology addresses the analytical limits of each tool.

Photocatalytic oxidation of DBP precursors using UV with suspended and fixed TiO2.

French River water (Nova Scotia, Canada) was separated into six different natural organic matter (NOM) fractions, including hydrophobic acids, bases and neutrals and hydrophilic acids, bases and neutrals. The raw water, as well as each of the NOM fractions were analysed for disinfection by-product (DBP) formation potential before and after advanced oxidation with UV/TiO(2) to determine the efficacy of this treatment for the removal of DBP precursors. The UV/TiO(2) treatment was carried out with a nanostructured thin film (NSTF), coated with TiO(2) which is compared with the use of a TiO(2) suspension. For the raw river water, removals of total trihalomethane formation potential (TTHMFP) and total haloacetic acid formation potential (THAA(9)FP) were found to be approximately 20% and 90%, respectively, with 50 mJ/cm(2) UV exposure and 1mg/L TiO(2). For the fractionated samples, approximately 75% of both trihalomethane (THM) and haloacetic acid (HAA) precursors were found to be associated with the hydrophobic acid fraction. For this individual fraction the same UV/TiO(2) treatments exhibited approximately 20-25% removal of both TTHMFP and THAA(9)FP, suggesting that the fractionation process may have affected the treatability of HAA precursors or may have altered the results of the oxidation processes.