Characterization and removal of dissolved organic matter in a vertical flow constructed wetland

•DOM fractions and removal rates were characterized in a constructed wetland.•DOM fractions >10kDa were preferentially removed from raw sewage in the constructed wetland.•Hydrophobic organics were removed more preferentially than hydrophilic organics.•Acidic and neutral organic matters had higher removal rates than basic matters.•Protein-like substances contributed substantially to total DOC removal in the constructed wetland. Isolated dissolved organic matter (DOM) fractions and their removal potentials in a vertical flow constructed wetland were characterized and identified. Resin isolation, molecular weight distribution and three-dimensional excitation–emission matrix (EEM) fluorescence spectroscopy were used to characterize DOM in raw sewage and treated effluent. The results showed that DOM fractions with molecular weights >10kDa in raw domestic sewage could be removed from the system more preferentially. Compared with hydrophilic organics, hydrophobic organics tended to be removed in the vertical flow constructed wetland more preferentially. Acidic and neutral organic matters featured higher removal rates than that of basic matters. Protein-like substances were representative of the biodegradable DOM, which made up a substantial proportion of the total dissolved organic carbon (DOC) removed from the system, while visible fulvic-like hydrophilic substances represented non-biodegradable DOM, which made up a minor proportion of the total DOC removed from the vertical flow constructed wetland.