Membrane fouling remains a major challenge for wider application of membrane bioreactors (MBRs) to wastewater treatment. Membrane fouling is mainly caused by microorganisms and their excreted microbial products. For development of more effective control strategies, it is important to identify and characterize the microorganisms that are responsible for membrane fouling. In this study, 41 bacterial strains were isolated from fouled microfiltration membranes in a pilot-scale MBR treating real municipal wastewater, and their membrane fouling potentials were directly measured using bench-scale cross-flow membrane filtration systems (CFMFSs) and related to their cellular properties. It was found that the fouling potential was highly strain dependent, suggesting that bacterial identification at the strain level is essential to identify key fouling-causing bacteria (FCB). The FCB showed some common cellular properties. The most prominent feature of FCB was that they formed convex colonies having swollen podgy shape and smooth lustrous surfaces with high water, hydrophilic organic matter and carbohydrate content. However, general and rigid biofilm formation potential as determined by microtiter plates and cell surface properties (i.e., hydrophobicity and surface charge) did not correlate with the fouling potential in this study. These results suggest that the fouling potential should be directly evaluated under filtration conditions, and the colony water content could be a useful indicator to identify the FCB.
Bibliographical noteFunding Information:
The authors would like to thank to Mr. Yusuke Ikawa and Mr. Takatomo Ohta for technical assistance. This work has been supported by Core Research of Evolutional Science and Technology (CREST) project ( Development of Innovative Water and Wastewater Treatment Systems for Sustainable Urban Water Metabolism ) of Japan Sciences and Technology Agency (JST), which was granted to S. Okabe and Grant-in Aid for JSPS Fellows ( 2600217604 ) of the Japan Society for the Promotion of Science . The authors acknowledge Mitsubishi Rayon Co., Ltd., Toyohashi, Aichi 440-8601, Japan for kindly constructing and providing the CFMFS.
- Colony water content
- Cross-flow filtration system
- Fouling-causing bacteria (FCB)
- Hydrophilic organic matter
- Membrane fouling potential