Mechanisms Analysis of Ultrafiltration Membrane Biofouling and Alleviation: From Viewpoints of Eps Composition and Microbial Interaction Energy

Abstract

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. We found that a stronger fouling degree was induced by Pseudomonas putida (rod-shaped) than that induced by Staphylococcus aureus and Enterococcus faecalis (sphere), which was mainly due to higher concentration of loosely bound EPS with apparent molecular weight smaller than 1 kDa. The computational fluid dynamics results suggested that the larger membrane filtration resistance caused by P. putida was due to more EPS secretion. According to the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, higher interaction energy was induced because of the higher content of polysaccharides (e.g., hydroxyl groups) and proteins (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 treatment, resulting in fouling alleviated. This work will be beneficial for further biofouling control in actual water treatment plants.

Keywords: Ultrafiltration, biofouling, EPS, Microbial interaction, UV treatment