Ultrafiltration fouling behavior of natural organic matter: a perspective of EEM and molecular weight distribution

As natural organic matter (NOM) can cause serious ultrafiltration (UF) membrane fouling, most previous studies on UF fouling caused by NOM focused on the contribution of NOM characteristics. In this study, the correlation of molecular weight and fluorescence characteristics was examined and the fouling behavior of NOM was examined in a comprehensive manner through a lot of analysis including redundancy analysis (RDA), parallel factor analysis (PARAFAC) and atomic force microscopy (AFM). The results showed that NOM from Tong Xin river was composed of humic acid (500 Da–8,000 Da), tryptophan-like substance, soluble microbial product (SMP) and aromatic protein (600,000 Da–2,000,000 Da). Notably, UF performance was significantly affected by the humic acid-like substance. Concurrently, the combined mechanism (CM) model was adopted to evaluate the fouling mechanism of NOM. The results indicated that the cake-intermediate model played an important part during membrane fouling and the cake layer fouling had a larger predominance over the intermediate blocking, which can be further proved in the membrane morphology detection.