碩士 / 國立成功大學 / 環境工程學系碩博士班 / 96 / In water treatment process, low-pressure membrane can substitute for coagulation, sedimentation and sand filtration, but the main problem is fouling. According to the literature, when treating eutrophic source waters, the polysaccharide from extracellular polymeric substance (EPS) of algae could affect the operation of membrane process. Further, pretreatment with oxidants are commonly used in membrane process for biofouling control. However, oxidation may change the quantity and quality of EPS, and, therefore, may also change its effect on membrane fouling.
In this research, synthetic water, containing cyanobacteria (Microcystis sp.) and green algae (Chodatella sp.), was used to simulate the source water from eutrophic reservoirs. First, preoxidation with either potassium permanganate or ozone were conducted, the variation of extracellular mucilage with oxidants type and dosage was analyzed by fluorescent microscopic method. The variation of size distribution of algae-containing floc, and the quantity and quality of the soluble extracellular polymeric substance (EPS) before and after oxidation were also monitored. Then the algae-contained synthetic water and its filtrate through 0.45µm membrane filter, either with or without preoxidation, were filtered through UF membrane (regenerated cellulose). Both the variation of flux with transmembrane pressure and the decreasing of flux with the cumulated permeate volume were monitored. Finally ATR-FTIR was used to study the functional groups of the possible foulants on UF membranes.
The results show that Microcystis sp. has higher amount of EPS than that of Chodatella sp. Preoxidation was found to increase the concentration of soluble EPS of both algae species. Both potassium permanganate and ozone would increase the carbohydrate concentration in the soluble EPS of Chodatella sp., but their effects on protein were minor. For Microcystis sp., the effect of potassium permanganate on carbohydrate and protein was minor, while ozone would significantly increase the concentration of both. As far as the effect on UF membrane fouling is concerned, preoxidation was found to have minor effect on the fouling caused by Chodatella sp. While both permanganate and ozone would aggravate the fouling caused by Microcystis sp., the effect of ozone was more significant than that of permanganate. Further, based on ATR-FTIR spectrum, more organic compounds also could be detected on the fouled UF membrane after treating preozonated solution containing dissolved EPS from Microcystis sp., compared to those from Chodatella sp.
Next, Hermia’s model was used to perceive membrane fouling mechanism. Those caused by suspension and soluble EPS of Microcystis sp.were found to be dominated by different degree of pore blocking. While those caused by Chodatella sp. could not be determined at this stage.
When the soluble EPS contained solution, which was prepared from permanganate preoxidated Chodatella sp. suspension, was filtered through UF membrane, no fouling was noticed during the testing period. However, brown particles, probably MnO2(S) from the reduced permanganate, were accumulated on membrane surface. Therefore, it was assumed that the reducing product from permanganate probably would not cause membrane fouling.
| Identifer | oai:union.ndltd.org:TW/096NCKU5515031 |
| Date | January 2008 |
| Creators | Meng-ling Hsieh, 謝孟伶 |
| Contributors | Hsuan-Hsien Yeh, 葉宣顯 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 115 |
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