Assessment of Fouling Potentials of Extracellular Polymeric Sub-stances in a Membrane Bioreactor Using Modified Fouling Index(MFI)

Yisong Hu, Xiaochang C. Wang, WenruiTian, RongChen



Fouling potentials of extracellular polymeric substances represented by MFI were assessed in a full scale membrane bioreactor (MBR) treating domestic wastewater. Total EPS were divided into soluble EPS (SEPS), loosely bound EPS (LBEPS) and tightly bound EPS (TBEPS) by a series of extraction methods. The components and properties of three types of EPS were examined by colorimetric methods and three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy. Fouling potentials of EPS were measured by batch filtration tests with MFI as an indicator. The results showed that the majority of total EPS was TBEPS, which accounted for nearly 90% of the total EPS. In addition, LBEPS with the lowest content demonstrated the highest membrane rejection rate during filtration. EEM spectra analysis confirmed the components measurement of EPS and further revealed that tryptophan protein-like substances could be of significant importance. MFI of total sludge rather than individual component was significantly related to real MBR fouling rate (dTMP/dt). TBEPS showed the highest potential to foul the membrane; however, LBEPS contributed most to membrane fouling since they had the highest specific MFI and similar filtration behavior as activated sludge.


Keywords: Full scale membrane bioreactor; membrane fouling; extracellular polymeric substances;
modified fouling index; fouling potential