Characteristics of different fractions of microbial flocs and their role in membrane fouling

摘要

Characteristics of different fractions (small flocs vs. large flocs) of sludge flocs from a submergednanaerobic membrane bioreactor treating thermomechanical pulping (TMP) whitewater werendetermined using various analytic techniques, including extraction and chemical analysis ofnextracellular polymeric substances (EPS), particle size analyzer, and polymer chain reactionn(PCR)-denaturing gradient gel electrophoresis (DGGE). The results showed that the fraction ofnsmaller flocs contained a higher level of bound EPS and had a higher fractal dimension asncompared to the fraction of larger flocs. PCR-DGGE analysis indicated that there were significantndifferences in microbial community between the fraction of smaller flocs and large flocs. Thenmicrobial community of the smaller flocs was similar to that of the sludge cake layers, indicatingnthe pioneering role of the microbial community in smaller flocs in membrane fouling. Thesenfindings provide a new insight in the difference of membrane fouling potential between smallernflocs and larger flocs fraction.