碩士 / 國立成功大學 / 環境工程學系碩博士班 / 94 / In Taiwan, over 65% of source water for public water supply is from reservoir. Owing to eutrophication, the growing of algae in the reservoir is quite common. Algae can cause water quality problems such as taste and odor and/or toxicity. During water treatment, if algae are not removed by coagulation and sedimentation, some species may clog filter. Some algae cells can penetrate filter media, and cause water quality deterioration in distribution system.
In this study, two pure-cultured species, namely Navicula sp. (diatom) and Microcystia sp. (blue-green algae) were used to prepare algal suspension with background ionic strength provided by 0.015 M NaClO4.The effect of preoxidation by ozone and potassium permangate, and the existence or not of calcium ion on algae cells settling and their coagulation and sedimentation was focused.
The results show that potassium permangate was more effective than ozone for diatom cells settling and their coagulation and sedimentation by alum. When calcium ions were added into the algal suspension, the residual algal cell concentrations in the supermatants after settling were reduced, no matter that preoxidants were used. However, this phenomenon was more prominent for potassium permangate than ozone. For blue-green algae, the cells always float, it did not matter if preoxidant or calcium ions were added or not. However, with the coexistence of calcium ions and potassium permangate, the color of the algal suspension was turned yellowish-brown, compared to the light purple when only potassium permangate was added. The explanations for these phenomena were that positively charged calcium ions can promote the adsorption of MnO2, the reduction product of permangate onto algae cell surface, both were negatively charged under neutral pH value. And the color of MnO2 is yellow-brown.
Based on the observation by SEM, high ozone dosage was found to cause the disintegration of diatom cells and the rupture of mucilage layer of blue-green algae. Both would cause the increase in dissolved organic concentration and, therefore, the NPDOC value of the aqueous phase. Those organics would compete with algae cells for coagulants during the coagulation process, and have detrimental effect on algae coagulation removal.
| Identifer | oai:union.ndltd.org:TW/094NCKU5515035 |
| Date | January 2006 |
| Creators | Chien-yi Tsai, 蔡倩誼 |
| 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 | 99 |
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