Membrane ultrafiltration (UF) is on the rise in the water industry because it provides good removal of turbidity, particulates, and microorganisms. However, membrane fouling has been viewed as a limitation to the wide usage of membranes. Fouling necessitates periodic chemical cleaning and as a result, causes an increase in the amount of energy and overall cost for operation. Dissolved organic matter (DOM) has been identified as one of the major causes of fouling during membrane ultrafiltration, specifically the protein-like constituents. There is a need in the water industry to understand the changes in DOM due to fouling during membrane ultrafiltration. In this study, we used a pilot scale UF membrane (0.03 μm pore size) and different synthetic wastewater solutions as feed water. We evaluated the effects of biofilm formation on the retention of different organic compounds by the UF membrane by measuring dissolved organic carbon, total dissolved nitrogen, and bulk protein concentrations as well as DOM fluorescence spectra and peak intensities to characterize the feed, permeate, and backwash during UF membrane fouling. To evaluate ultrafiltration with and without the formation of a biofilm, two synthetic wastewater solutions, one with bacteria and one sterilized with hypochlorite, were run through a UF membrane over several cycles. Results thus far indicate that ultrafiltration for both solutions preferentially removed the protein-like components compared to the humic-like components. For the unsterilized solution experiment, the results suggest that the concentration of proteins, DOC, and TDN were low immediately after backwash, but increased as the membrane pressure increased. However, in the sterilized experiment, results were more variable and did not follow this trend. Therefore, the biofilm appears to be involved in processes that initially retain compounds but later, release compounds into the permeate. These initial results and findings are important for understanding the constituents retained and released by UF membranes under fouling conditions.

Analysis of organic compound permeability in relation to ultrafiltration membrane fouling

255th National Meeting (2018)

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