pH Effects on Ceramic Membranes Fouled by Extracellular Polymeric Substances
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Date
2016-05
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The Ohio State University
Abstract
Biofouling has proven to be a primary challenge for membrane filtration. Biofouling occurs when microbes secrete extracellular polymeric substances (EPS) which adhere to membrane surfaces. EPS impede the flow of treated water through membrane pores, resulting in increased pressure demands and operation costs. Importantly, the protein to polysaccharide ratio of EPS affects its propensity to adhere to surfaces. However, the effects of pH on EPS adherence have not been investigated over a broad pH range. This study investigates how pH affects the composition of EPS fouling layers that have been cleaned with ultrasound. This is significant because ceramic membrane technology allows for filtration at previously unfeasible pH levels, and it is unknown how operation under these pH conditions will affect fouling layer composition. In this study, 0.2 micron Whatman Anodisc ceramic membranes were fouled with EPS solution. During each filtration, flux measurements were taken. Membranes then underwent either timed sonication or no sonication. During filtration and sonication, pH was kept constant at a value of 3.5, 6.9, or 9.5. Confocal laser scanning microscopy, in conjunction with MATLAB image analysis, compared protein and polysaccharide intensities of each fouling layer. It was found that fouling layers initially exhibit a wide variety of protein to polysaccharide ratios, and that preferential removal of regions high in proteins occurs at pH 3.5. Additionally, EPS solutions exhibited faster filtration rates at pH 3.5 than at other pH values. Results were attributed to pH-mediated interactions between EPS components and the membrane surface and structural conformations of EPS.
Description
3rd place winner, 2016 Denman Undergraduate Research Forum
Keywords
biofouling, EPS, membrane, ultrasound, ceramic, pH