Characterization of natural organic matter in drinking water: Sample preparation and analytical approaches

Natural organic matter (NOM) is present in source water worldwide, and it is composed of numerous organic compounds produced in natural processes. NOM has been drawing increasing concerns because it not only affects drinking water treatment on many aspects (e.g., the performance of treatment techniques, necessity of advanced treatment, the dose of treatment chemicals, etc.), but also acts as the main precursor of hazardous drinking water disinfection byproducts (DBPs). Accordingly, to optimize treatment processes and to control the formation of DBPs, it is vital to analyze and characterize NOM for a better understanding of its property and reactivity. In this review, a summary of methods used in NOM analysis and characterization during drinking water treatment was provided, including analysis methods for general parameters (e.g., dissolved organic carbon, dissolved organic nitrogen, (specific) ultraviolet absorbance, fluorescence, polarity, and zeta potential) and characterization methods for elemental and structural identification (e.g., elemental analysis, Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, pyrolysis-gas chromatography/mass spectrometry, liquid chromatography/mass spectrometry, and Fourier transform ion cyclotron resonance mass spectrometry). In addition, preparation and pretreatment methods for NOM were also covered in this review, including isolation and concentration methods (reverse osmosis, pressure-reducing evaporation, freeze-drying, and electrodialysis) as well as fractionation methods (size exclusion chromatography, resin fractionation, membrane filtration, polarity rapid assessment, field-flow fractionation, and reversed-phase high performance liquid chromatography).