Ultrafiltration (UF) membrane fouling caused by cyanobateria: Fouling effects of cells and extracellular organics matter (EOM)

The ultrafiltration (UF) membrane fouling caused by cyanobacterial cells and extracellular organic matter (EOM) was investigated in this study. Flux decline and reversibility of fouling caused by cyanobacterial cells (including live cells and cell fragments), EOM and their combination were compared. UF fractionation and XAD resin adsorption were employed to characterize the molecular weight (MW) distribution and hydrophilicity/hydrophobicity of EOM, respectively. Attenuated total reflection-Fourier infrared spectroscopy (ATR-FTIR) spectroscopy and scanning electron microscope (SEM) were utilized to characterize the membranes fouled by cyanobacterial cells and EOM. Results showed that cells and cell fragments caused not only reversible but also irreversible fouling of UF membrane. Besides, the membrane fouling caused by the cells and cell fragments was characterized by secondary sharp flux decline which was related to the compression of cake layer. Cyanobacterial EOM also caused serious flux decline due to the deposit of macromolecular organics such as proteins and polysaccharides on membrane. Moreover, EOM could lead to serious irreversible membrane fouling probably due to adhesion of proteins which were characterized by hydrophobicity. Additionally, UF membrane fouling was exacerbated when cells and EOM were filtered together, but no synergetic fouling occurred in this study.

► We examined the membrane fouling effects of algae cells, EOM and their combination.
► Algal cells and cell fragment could cause both reversible and irreversible fouling.
► Fouling caused by algae cells was characterized by sharp secondary flux decline.
► EOM led to serious irreversible fouling probably due to adhesion of proteins.
► UF membrane fouling was exacerbated when cells and EOM were filtered together.