This study investigated distinguishing characteristic of dissolved organic matter (DOM) in MBR and AAO effluents by OF fractionation, XAD-8 resin adsorption isolation, excitation and emission matrix fluorescence spectroscopy and fourier transform infrared spectroscopy analysis. Halogenated carbonaceous and nitrogenous disinfection byproducts (DBPs) especially N-nitrosodimethylamine (NDMA) formation reactivity of various DOM fractions were also analyzed. Results showed that although the MBR effluent contained lower DOM than the AAO effluent, more halogenated C, N-DBPs in the MBR effluent were formed than in the AAO effluent after chlorination due to its higher percentage of molecular weight (MW) > 1 kDa materials, fulvic acid-like substances and polysaccharides. For example, the content of TCM in MBR effluent was high as 526 pg/mg-C, which was about 13 times as that in AAO effluent. In contrast, the NDMA yield of MO effluent was more than that of MBR effluent because AAO contained higher percentage of MW < 1 kDa materials, aromatic proteins, polypeptides and amino acids especially secondary amines. (C) 2017 Elsevier B.V. All rights reserved.