Unraveling the interaction of algogenic organic matter and cells on membrane fouling mechanism during treatment of Microcystis aeruginosa-laden water

Membrane technology is widely used for algal bloom treatment due to its effective separation capabilities. However, the effect of algal cell interaction with AOM on the membrane fouling mechanism remains unclear. This study systematically investigated the filtration characteristics of algal cells and AOM, individually and in combination. The mechanism of membrane fouling was explored through the distribution of organic components, algal cake structure, interfacial free energy, and changes in the functional groups in cross-fouling. The mitigation effects of pretreatment additives, including diatomite, powdered activated carbon (PAC), and plant cotton, on interaction fouling were evaluated. The results revealed that the interaction between algal cells and AOM had a synergistic effect, significantly increasing membrane resistance. The presence of algal cells facilitated the transformation of some irreversible fouling into reversible fouling. Compared with cells, AOM exhibited higher adhesion-free energy with the membrane, with higher AOM concentrations notably elevating both Ri and Rir. Confocal laser scanning microscopy (CLSM), scanning electron microscope, and atomic force microscope (AFM) observations revealed that protein volume fractions increased with cake layer thickness during cross-fouling, while polysaccharides preferentially deposited on the membrane surface. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses further indicated that polysaccharides are critical in membrane fouling, while proteins were more likely to cause reversible fouling within the cake layer. Notably, diatomite significantly reduced the interaction fouling coefficient by optimizing the cake layer structure. These findings provide valuable insights for controlling membrane fouling based on the characteristics of cells and AOM.