Fractionation of Natural Organic Matter in Drinking Water and Characterization by¹³C Cross-Polarization Magic-Angle Spinning NMR Spectroscopy and Size Exclusion Chromatography

Abstract

Natural organic matter from drinking water sources was fractionated, and the fractions were characterized by NMR and SEC with the aim of relating NOM structure to treatability. Organic matter was isolated from two Australian surface waters (Horsham, Moorabool) by reverse osmosis and from a groundwater (Wanneroo) by anion exchange. The isolates were fractionated according to polarity and charge by resin adsorption. 13C NMR spectra of the freeze-dried fractions showed the most hydrophobic fraction to be high in aliphatic and aromatic carbon while slightly hydrophobic organics have more carbonyl and alkoxyl carbon. The Horsham and Wanneroo hydrophilic fractions show strong alkoxyl signals attributed to carbohydrate. Moorabool hydrophilics contain aromatic (phenolic) carbon; the apparent absence of carbohydrate appears to be an artifact. Size-exclusion chromatograms were recorded on the original and fractionated organics with both UV and dissolved organic carbon detection. The Horsham and Moorabool organics have similar molecular size distributions while Wanneroo is dominated by strongly absorbing species having large hydrodynamic radii. The hydrophobic and charged hydrophilic fractions also have high apparent MW, while the neutral fraction is higher in low-MW compounds of relatively low specific absorbance, suggestive of carbohydrates.

Effect of NOM characteristics and membrane type on microfiltration performance

“…It was assumed that this component of NOM reports predominantly to the hydrophilic fraction of NOM as it is composed of polysaccharide based material (Croué, 2004 ). This is consistent with the previous NMR analysis of NOM (Wong et al, 2002).…”

“…Meredith water was much higher in the SHA fraction at the expense of the WHA material; otherwise the compositions were rather similar. Evidence from solid state 13 C nuclear magnetic resonance spectra (Wong et al, 2002) has previously shown the hydrophobic fractions to be high in aliphatic and aromatic carbon, while the weakly hydrophobic organics have more carbonyl and alkoxy carbon. Hydrophilic fractions show strong alkoxy signals attributable to carbohydrates, while for one water phenolic carbon was present.…”

Characterization of dissolved organic matter using high-performance liquid chromatography (HPLC)–size exclusion chromatography (SEC) with a multiple wavelength absorbance detector

“…In principle, the separation of molecules in a SEC column is based on size, and compounds with lower AMW are eluted later than those with higher AMW. However, the interpretation of HPLC-SEC data is greatly affected by the type of post-column detection used (Her, 2003;Korshin et al, 2009), typically UV absorbance, fluorescence, or multi-angle light scattering (MALS) (Baker, 2001;Wong et al, 2002;Her, 2003;Allpike et al, 2005;Akagi et al, 2007;Liu et al, 2010a). Post-column absorbance detection is most common due to its sensitivity and relatively low cost (O'Loughlin and Chin, 2001;Her et al, 2002bHer et al, , 2008Hur and Kim, 2009).…”

Changes in the quality of river water before, during and after a major flood event associated with a La Niña cycle and treatment for drinking purposes

“…The approach of using high coagulant doses for this purpose has been previously reported (Kastl et al, 2004;Chow et al, 1999). For organics remaining in post-treated waters, a range of characterization methods can be used, including those applied in this study, as well as Pyrolysis-GC/MS, resin fractionation and 13 C NMR (Chow et al, 1999;Gadel and Bruchet, 1987;Wong et al, 2002).…”