Microcystis aeruginosa removal using nanosilicate platelets in eutrophicated water bodies

近年來水庫湖泊受污染使優養化現象頻繁發生逐漸受重視，目前在台灣本島共計有 21 座主要水庫，大部分水庫過去皆有優養化情況發生，外島 34 座水庫中有 30 到33 座水庫呈現長年優養化；中國則以長江中下游與西南省區水體優養化情況較嚴重；美國五大湖與其海岸優養化也日益嚴重。優養化造成藻類增生，其中以會產生微囊藻毒之微囊藻造成安全疑慮為近年來水源管理重要議題，現有淨水處理程序如加氯消毒會造成藻體破壞使毒素釋出或混凝沉澱對於溶解性毒素去除效果不佳等困難，因此本研究欲開發一成本低廉且能有效抑制微囊藻生長與其毒素去除之技術。 本研究所使用奈米矽片為天壤土壤經特殊方法製成奈米尺寸材料，在經界面活性劑改質後已有研究結果顯示對於細菌具有相當程度抑制效果。本研究以奈米矽片對培養純藻種之微囊藻進行生長抑制劑量效應的研究，結果顯示在 10 ppm 劑量下即可有效抑制微囊藻生長，並隨著劑量上升對於微囊藻生長抑制速率也隨之上升。水質檢測中濁度也是相當重要項目之一，因此本研究中使用常見混凝劑硫酸鋁與氯化鐵及奈米矽片進行混凝實驗，以低濁度（40 NTU）與高濁度（300-400 NTU）作探討，在低濁度部分低劑量（1 ppm）以傳統混凝劑有較佳效果；在高濁度部分傳統混凝劑使用劑量提升至 50-100 ppm 才能有較佳去除效果，而奈米矽片效果雖然比不上傳統混凝劑，但在 100 ppm 劑量有60% 濁度去除率，表示奈米矽片作為微囊藻整治時不但具有生長抑制效果同時具有濁度去除之能力。 微囊藻所造成另一個問題為其產生之微囊藻毒素，因此本研究以奈米矽片進行批次吸附實驗，了解奈米矽片劑量對 microcsytin-LR 吸附能力，結果顯示隨著奈米矽片劑量上升對於 microcystin-LR 吸附量也隨之上升，在 100 ppm 劑量去除率可達到 47% 當劑量為 500 ppm 去除率則高達 99% 結果顯示奈米矽片亦可良好去除微囊藻所產生之毒素。考慮未來實際應用時對於環境生態的衝擊，本研究以Bacillus halodurans與 Escherichia coli 作為葛蘭氏陽性菌及陰性菌的代表，了解奈米矽片對其影響，在 E. coli 結果中顯示與微囊藻相似生長抑制情形；而 B. halodurans 結果卻相反，隨著奈米矽片劑量上升，細胞濃度生長至越高顯示奈米矽片可幫助生長，顯示奈米矽片作為生長抑制藥劑對於環境中細菌是具有選擇性。 在本研究中以掃描式電子顯微鏡（scanning electron microscope, SEM）進行微囊藻生長抑制實驗中菌體表面觀察，其結果可看出對於微囊藻細胞表面會造成破損，未來將進一步探討其生長抑制機制。In recent decades, eutrophication of water reservoirs and lakes has drawn much attention. Currently, there are 21 major water reservoirs on Taiwan''s main island, and 34 on its isolated islands. Most of these water reservoirs on main island have been identified as eutrophic and 30 to 33 out the 34 on isolated island have been identified as eutrophic. In China, the most seriously eutrophic lakes are at the downstream of Yangtze River and at the southwestern provinces. The Great Lakes at USA are also threatened by eutrophication. Coming along with eutrophication, the proliferation of algae, especially toxin-generating Microcystis aeruginosa, poses safety concerns in drinking water supply. Water treatment plant usually use chlorination to tackle this problem by breaking the algal cells. However, the released algal toxin cannot be easily removed by coagulation or flocculation. In the meantime, this measure may also generate disinfection byproducts, such as trihalogenated carbon. This study is aimed to develop a technology for effective inhibition of Microcystis aeruginosa and removal of released microcystin LR, the most toxic form of all toxins generated by Microcystis aeruginosa. The material used in growth inhibition test is nanosilicate platelet (NSP) derived from natural clay minerals. At as low as 10 ppm, NSP demonstrated strong growth inhibition effect. The effects seem to be direct proportional to the dosage. However, similar dosage on two other bacteria, one Gram positive and one Gram negative, showed very different results implying that the growth inhibition effect of NSP could be selective. Two sets of turbidity tests were carried out and traditional coagulant, trivalent aluminum and trivalent iron showed much better results than NSP. However, the results clearly support that NSP is still a good candidate at high turbidity since aluminum and iron are not favored to be added into the water reservoirs directly due to health hazards and taste problems. A toxin adsorption test has been conducted to see if NSP can effectively remove microcystin-LR. The results showed that at 100-ppm and 500-ppm dosages, the removal is 47% and 99%, respectively, suggesting NSP can serve as a very good adsorbent for microcystins.摘要………………………………………………………………………i Abstract…………………………………………………………………ii 目錄…………………………………………………………………iii 圖目錄……………………………………………………………………vi 表目錄……………………………………………………………………ix 第一章 前言……………………………………………………………1 1-1 研究緣起………………………………………………………1 1-2 研究目的………………………………………………………2 第二章 文獻回顧………………………………………………………3 2-1優養化現象與對淨水程序之影響……………………………………3 2-2 藍綠藻與藍綠藻毒素…………………………………………………5 2-3 微囊藻與微囊藻毒素…………………………………………………9 2-4 藻類毒素的危害與國內外水體中流佈情況…………………………12 2-5 水庫湖泊中藻類去除方法……………………………………………15 2-5-1 化學處理法………………………………………………………15 2-5-2 生物控制…………………………………………………………16 2-5-3 曝氣循環法………………………………………………………17 2-5-4 浮除法……………………………………………………………17 2-5-5 大麥桿……………………………………………………………17 2-5-6 奈米銀……………………………………………………………18 2-5-7 生物界面活性劑…………………………………………………18 2-5-8 改質黏土…………………………………………………………18 2-5-9 光觸媒……………………………………………………………19 2-5-10 植物剋他物質…………………………………………………20 2-6 淨水處理程序中藻類去除……………………………………………20 2-6-1 前氧化處理………………………………………………………20 2-6-2 混凝程序…………………………………………………………22 2-6-3 混凝與膠凝與相關理論…………………………………………22 2-6-4 混凝之影響因子…………………………………………………25 2-6-5 鋁鹽之混凝………………………………………………………26 2-6-6 鐵鹽之混凝………………………………………………………27 2-6-7 混凝對微囊藻與藻毒處理效果…………………………………28 2-6-8 其他淨水程序對於藻毒之去除效果……………………………29 2-6-9 各項處理程序彙整………………………………………………30 2-7 國內外分析藻類毒素技術之比較……………………………………31 2-8 奈米矽片………………………………………………………………34 2-8-1 黏土結構…………………………………………………………34 2-8-2 黏土的性質………………………………………………………36 2-8-3 奈米矽片製備與改質……………………………………………37 第三章 研究方法……………………………………………………………40 3-1 實驗設備………………………………………………………………40 3-2 實驗藥品………………………………………………………………41 3-3 實驗架構………………………………………………………………42 3-4 微囊藻培養……………………………………………………………43 3-4-1 微囊藻之來源……………………………………………………43 3-4-2 微囊藻培養方法…………………………………………………43 3-5 微囊藻計數……………………………………………………………44 3-6 奈米矽片微囊藻生長抑制實驗………………………………………45 3-6-1 生長抑制實驗微囊藻之準備……………………………………45 3-6-2 微囊藻生長抑制實驗……………………………………………45 3-7 瓶杯試驗………………………………………………………………46 3-8 細菌生長抑制實驗……………………………………………………47 3-8-1 純菌培養…………………………………………………………48 3-8-2 總菌數分析-濾膜法………………………………………………49 3-9 毒素吸附實驗…………………………………………………………49 3-10 藻類毒素分析方法－LC/MS-MS…………………………………50 3-10-1 固相萃取技術…………………………………………………50 3-10-2液相層析串聯質譜儀……………………………………………51 3-11 微囊藻細胞觀察……………………………………………………51 第四章 結果與討論…………………………………………………………52 4-1 微囊藻生長抑制實驗………………………………………………52 4-1-1 低微囊藻密度……………………………………………………52 4-1-2 中等微囊藻密度…………………………………………………53 4-1-3 高微囊藻密度……………………………………………………54 4-1-4 微囊藻生長抑制實驗綜合討論…………………………………55 4-2 瓶杯實驗……………………………………………………………59 4-2-1 低濁度硫酸鋁混凝………………………………………………59 4-2-2 低濁度氯化鐵混凝………………………………………………60 4-2-3 低濁度奈米矽片混凝……………………………………………61 4-2-4 高濁度硫酸鋁混凝………………………………………………62 4-2-5 高濁度氯化鐵混凝………………………………………………63 4-2-6 高濁度奈米矽片混凝……………………………………………64 4-2-7 瓶杯實驗綜合討論………………………………………………65 4-3 細菌生長抑制實驗…………………………………………………66 4-3-1 Bacillus halodurans 生長抑制實驗……………………………66 4-3-2 Escherichia coli 生長抑制實驗…………………………………70 4-3-3 細菌生長抑制實驗綜合討論……………………………………73 4-4 微囊藻毒素吸附……………………………………………………74 4-4-1 microcystin-LR 檢量線與偵測極限……………………………74 4-4-2 微囊藻毒素吸附實驗……………………………………………74 4-4-3 微囊藻毒素吸附實驗綜合討論…………………………………76 4-5 細胞 SEM 觀察結果………………………………………………77 4-5-1 微囊藻 SEM 觀察結果………………………………………78 4-5-2 Escherichia coli 細胞觀察……………………………………81 4-5-3 Bacillus halodurans 細胞觀察…………………………………83 第五章 結論與建議…………………………………………………………86 5-1 結論…………………………………………………………………86 5-2 建議…………………………………………………………………87 參考文獻……………………………………………………………………8