Characteristics of dissolved organic matter in surface water and fouling mechanisms during the ultrafiltration

To learn about the characteristics of dissolved organic matters (DOM) in the surface water and identify the main foulants during the ultrafiltration (UF), the Ganjiang River was subjected to UF. Hydrophilicity and hydrophobicity, molecular weight distribution, and fluorescence characteristics of the surface water in the Ganjiang River were studied. Classification results showed that the DOM of the Ganjiang River was mainly hydrophobic (HPO) and a neutral hydrophilic fraction (N-HPI), which accounted for 40.06% and 29.69%, respectively. However, the proportions of transphilic (TPI) and charged hydrophilic fraction (C-HPI) were 18.91% and 11.33%, respectively. The fluorescence excitation-emission matrix illustrated that the Ganjiang River contained both humus-like organics and soluble microbial products with high response intensity and some protein-like organics which had weak response intensity. The membrane fouling test found HPO and N-HPI tended to cause a relatively large specific flux decrease, but a smaller degree of specific flux decline caused by TPI and C-HPI. The reversibility of membrane fouling revealed that HPO and N-HPI could easily cause irreversible fouling, while the TPI and C-HPI also contributed to irreversible fouling. The fitting results of the Hermia model indicated that standard blocking and cake filtration was the main membrane fouling mechanisms in the initial stage of filtration.