Microbial interaction energy and EPS composition influenced ultrafiltration membrane biofouling and the role of UV pretreatment

Biofouling is still an important factor limiting ultrafiltration further application, and previous mechanism analyses were mainly focused on extracellular polymeric substances (EPS) composition and concentration. In this study, both biofouling and alleviation mechanisms were further investigated in detail with three typical microorganisms, particularly toward the microbial interaction energy. The results showed that a stronger fouling degree was induced by Pseudomonas putida (rod-shaped) than that induced by Staphylococcus aureus and Enterococcus faecalis (sphere). The computational fluid dynamics results suggested that the larger membrane filtration resistance caused by P. putida was due to more EPS secretion. EPS composition and confocal laser scanning microscopy analysis indicated that polysaccharide in EPS played greater roles on the biofouling than protein. According to the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, higher interaction energy was induced because of higher content of polysaccharide (e.g., hydroxyl groups) and protein (e.g., aggregated strands of amide I band) in EPS from P. putida, resulting in a thicker biofilm and stronger biofouling degree than that caused by S. aureus and E. faecalis. In addition, both EPS secretion and microbial interaction energy were inhibited by UV pretreatment, resulting in fouling alleviated. This work will be beneficial for further biofouling control in actual water treatment plants.