Characterization of biopolymers isolated from a pilot-scale membrane bioreactor treating municipal wastewater

Abstract

Biopolymers have been widely recognized as playing an important role in membrane fouling in membrane bioreactors (MBRs). In-depth characterization of biopolymers in MBRs can provide important insights into membrane fouling. In this study, ultrafiltration was used to selectively isolate biopolymers (recovery rate: 70%) from a pilot-scale MBR treating municipal wastewater. The characteristics of the isolated biopolymers were compared against those of model substances, such as sodium alginate (SA) and bovine serum albumin (BSA), which have been used in many previous studies. Lipopolysaccharides (LPS), which have been proposed as alternative model polysaccharides for MBR fouling research, were also characterized. Batch filtration tests demonstrated that the isolated biopolymers had a considerably higher fouling potential than the model substances. A modified liquid chromatography with organic carbon detection (LC–OCD) analysis showed that the constituents of the isolated biopolymers had molecular weights of >1,000,000 Da. Such macromolecular constituents were only detected in LPS among the model substances. A Fourier-transform infrared (FTIR) analysis indicated various constituents for the isolated biopolymers, such as polysaccharides, proteins and lipids. A quartz crystal microbalance (QCM) analysis demonstrated that the isolated biopolymers had a high affinity to polyvinylidene fluoride (PVDF), explaining the high fouling potential of these biopolymers.