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This dissertation, Membrane Fouling of Activated Sludge by Xinlong, Shi, 史昕龍, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled Membrane Fouling of Activated Sludge submitted by Xin Long SHI for the degree of Master of Philosophy at the University of Hong Kong in August 2004 This study was conducted to investigate three key issues related to membrane fouling for the membrane bioreactor process: (1) effect of powdered activated carbon (AC), (2) degree of pore fouling, and (3) effects of extracellular polymers of activated sludge. Continuous experiments on filtration of activated sludge were conducted to investigate the effect of AC in filtration of activated sludge. Four sludge samples were tested in parallel: an as-is sludge served as control, plus three sludge samples dosed with individual additives, including inert diatomaceous earth, virgin AC, and AC pre- -1 sorbed with 112 mg-C-g of extracellular polymeric substance (EPS). Results showed that EPS of activated sludge caused membrane fouling, and thus adversely affected filtration resistance. Additives may reduce the filtration resistance of activated sludge, depending upon their EPS-sorbing capacity. As compared with the control, virgin AC 12 -1 reduced the filtration resistance of activated sludge by 22%, from 6.40.5x10 m to 12 -1 5.00.1x10 m, whereas the reduction was only 14% by the AC pre-sorbed with EPS and negligible by the inert diatomaceous earth. Pore fouling of four microfiltration membranes was investigated for the filtration of activated sludge using sonication as the means to remove the cake layer from membrane surface. Results showed that pore fouling was affected by membrane's microstructure, pore openings and hydrophilicity. For the track-etched polycarbonate (PC) membrane, there was no measurable pore resistance (R ) to filtration. For the three membranes with sponge-like microstructure, the respective R values were 0.3 x 11 11 11 -1 10, 1.3 x 10, and 16.4 x 10 m for polyvinylidene fluoride (PVDF), mixed cellulose esters (MCE), and polyethersulfone (PES). The PES membrane had the highest R due to its large pore openings (18-20m), whereas MCE had higher R p p than PVDF because of its higher hydrophilicity. The R of PES membrane accounted for 86% of the total resistance for its filtration of activated sludge; the corresponding values were merely 2% for PVDF and 11% for MCE. It increased with the suspended solids level of the activated sludge to the power of 0.56. Results further demonstrated that R -dominant membranes, such as PES, were unsuitable for the membrane bioreactors. The experiments on individual effects of the EPS constituents, i.e. polysaccharide, protein and humic substance, on fouling of microfiltration membrane by activated sludge were conducted. Results showed that polysaccharide was the major foulants retained on the membrane, compared with humic substance and protein. Of the three model constituents of EPS, agarose, representing polysaccharide, had the highest 16 -1 15 specific resistance of 1.13 1.2410 m-kg, followed by humic acid (1.4 1.610 -1 14 -1 m-kg ), representing humic substance, and BSA (DOI: 10.5353/th_b3073188 Subjects: Separation (Technology)Membrane reactorsSewage - Purification - Activated sludge process

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