Characterizing the molecular weight distribution of dissolved organic matter by measuring the contents of electron-donating moieties, UV absorbance, and fluorescence intensity

Abstract

Electron-donating moieties (EDM) have recently been used to characterize the redox properties and treatability of dissolved organic matter during water and wastewater treatment. In this study, size exclusion chromatography followed by a derivatization-spectrometric method was developed to determine the molecular weight (MW) distribution of EDM in dissolved organic matter. The relationships between EDM concentration and chromophore content (indicated by UVA254), fluorophore content (indicated by fluorescence), and dissolved organic carbon (DOC) concentration were analyzed for different MW fractions. In general, natural organic matter (NOM) showed higher total EDM concentration and higher EDM average MW than effluent organic matter (EfOM). For NOM, fractions with MW between 1.8 k and 6.9 k Da accounted for most of the EDM (45.4%–48.6%), followed by the fractions with MW 1.8 k Da (1.8 k Da) is 1.2–1.9 times of relatively low-MW (1.8 k Da) and lower MW (<1 k Da) preferentially resulted in benzoquinone formation and ring-cleavage, respectively. Keywords: Dissolved organic matter, Molecular weight, Electron donating moiety, Chromophore, Water treatment