The fouling of three common UF membranes: polyacrylonitrile (PAN), polyethersulfone (PES), and polyvinyl difluoride (PVDF), having different hydrophilic characteristics (43°, 76°, and 87° contact angle, respectively) and a similar morphology, was studied. The experiment was conducted in a high through-put lab scale AnMBR using real domestic wastewater under sub-critical flux for 30 days and with backwashing cycles and biogas sparging. The fouling was evaluated by monitoring the changes in trans-membrane pressure (TMP) of each membrane. In addition, the membranes were taken out after 1, 4, 8, and 30 days and each membrane was analyzed by ATR-FTIR and scanning electron microscopy (SEM) images and the extracellular substances (EPS) were extracted and the proteins, polysaccharides, and dissolved organic carbon (DOC) concentrations in the EPS were measured.
The TMP of the three membranes, as well as the concentrations of the different components in the EPS, were similar during the first few days of filtration, as was also seen in the ATR-FTIR spectra and SEM images. After several days, the TMP for the PES and the PVDF membranes rapidly increased, but remained relatively stable for the PAN membrane throughout the 30 days experiment. This was also evident by a much higher EPS on the PES and PVDF membranes compared with the PAN membrane. It is proposed that the low fouling of the PAN membrane was due to the combination of the relatively low hydrophilicity and the frequent physical cleaning (gas sparging and backwashing). Further research will focus on investigating other membranes and the effect of morphological parameters of fouling.
See more of this Group/Topical: 2018 North American Membrane Society Meeting: Oral Submissions