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年度	108	專案性質	實驗性質
專案類別	研究專案	研究主題	整治
申請機構	國立台灣大學	申請系所	環境工程學研究所
專案主持人	于昌平	職等/職稱	副教授
專案中文名稱	開發微藻膜生物反應槽進行重金屬污染地下水治理研究
中文關鍵字	微藻, 膜生物反應槽, 固定化微藻技術, 重金屬, 陶瓷膜
專案英文名稱	Development of microalgae-based membrane bioreactor for treatment of heavy metal contaminated groundwater
英文關鍵字	Microalgae, Membrane bioreactor, Immobilized microalgae, Heavy metal, Ceramic membrane
執行金額	900,000元
執行期間	2019/1/1 至 2019/12/31
計畫中文摘要	依土壤及地下水污染整治網的國內污染場址查詢資料顯示，台灣受重金屬污染的地下水中多含鉻、鎳、鉛、銅等，主要為工廠營運所造成的人為污染行為，污染來源包含電鍍製程、金屬加工、廢液或廢棄物處理等。而地下水重金屬污染除了造成環境與生態的危害，透過多種管道也會對人體造成健康上的危害。因此開發有效處理地下水中重金屬污染的技術勢在必行。本計畫提出利用微藻吸附重金屬的能力，並結合陶瓷膜生物反應槽具有截留微藻以大幅提高微藻培養密度的潛力，開發適於配合抽水處理法使用的微藻膜生物反應槽技術以達到有效處理地下水中的重金屬的目的。 本研究計畫分成三部分：(1)首先以批次實驗測試不同微藻對重金屬鉻、鎳、銅及鉛的去除能力。利用批次實驗、將不同濃度的重金屬加入微藻培養體系中，研究重金屬去除效果、吸附動力學分析、吸附機制分析、藻類數目變化，其他離子對重金屬去除的影響等；(2)將篩選到對重金屬有良好去除率的微藻，以陶瓷膜生物反應槽培養並連續進流人工模擬及現地受重金屬污染地下水，針對不同的水力停留時間下，考察重金屬的去除情況，並研究跨膜壓力變化及陶瓷膜積垢清洗方法；(3)結合膜生物反應槽及微藻固定化的技術，設計一個連續流之固定化微藻-膜生物反應槽系統。針對不同的水力停留時間及微藻固定化小球投加量進行考察重金屬的去除，並研究固定化微藻對跨膜壓力變化的影響。應用本技術在處理過後產生的微藻生物質具有資源化的潛力，進而促進未來循環經濟型的地下水重金屬污染處理模式。 本計畫根據微藻重金屬等溫吸附結果，顯示三種常見微藻包含小球藻、四尾柵藻、羊角月牙藻在2.5 mg/L的重金屬鎳、銅、鉛濃度可在1小時內即有重金屬吸附效果，惟於96小時吸附實驗發現，長時間的吸附重金屬有再溶出現象，以鎳金屬情況較為明顯，推測銅、鎳、鉛主要為可逆性之吸附行為，而鉻(Cr2O72-)由於帶負電位，其吸附行為較鎳、銅、鉛所需時間較長，通常隨時間增加可提高其吸附量，混合金屬可發現與文獻相似之重金屬競爭行為，以銅鎳競爭較為顯著，微藻細胞表面的官能基對於重金屬吸附扮演相當重要的腳色，而藻的濃度增加可增加其總吸附量，其平衡濃度亦越低，惟其重金屬單位吸附量會下降，且pH可影響藻類吸附行為，而固定藻量隨重金屬濃度的增加，其重金屬去除率下降，嗜熱嗜酸紅藻以Langmuir擬合的結果R2較Freundlich等溫吸附式佳。試驗結果顯示，小球藻、四尾柵藻、羊角月牙藻、嗜熱嗜酸紅藻、固定化材料及固定化藻球皆具有不同程度之重金屬吸附能力。 外掛式及沉浸式微藻膜生物反應槽皆可提供良好的重金屬吸附效果，薄膜亦具有維持穩定的出水水質之附加效能，而以沉浸式微藻膜生物反應槽操作較為簡單，薄膜可利用曝氣盤減緩薄膜積垢，以維持長時間的操作通量。實際地下水經微藻膜生物反應槽，槽內可達到95%以上之溶解性鎳的去除，系統可達96-98%去除率，系統之單位溶解性鎳吸附量由2 mg/g提升至5.95 mg/g，然溶解性鉻去除率隨時間由37%降至負值，推測重金屬鉻可能由還原沉澱物溶出或藻對於鉻吸附速率較慢等累積所致，其系統過濾前後水質有明顯之差異，若取代現地抽取受污染地下之水處理程序，可減少藥劑花費，後續亦可評估微藻資源化可行性，應有其實際應用之潛勢及優勢。
計畫英文摘要	It has been reported that groundwater in Taiwan is polluted by heavy metals, such as chromium, nickel, lead and copper, according to the soil and groundwater pollution remediation statistics from Taiwan EPA. The pollution is mainly caused by anthropogenic sources, especially the industrial factories. The pollution sources include metal manufacturing, metal processing, electroplating procedures, and other improper waste liquid or waste disposal. The groundwater pollution will not only cause adverse effects to the environment and ecosystem, but can also cause health hazards to humans through various pathways. Therefore, it is urgent to develop technologies to effectively deal with heavy metal pollution in groundwater. This proposal plans to utilize the ability of microalgae to adsorb heavy metals, by combining the potential of ceramic membrane bioreactors to retain microalgae to significantly increase the density of microalgae culture, and therefore, to develop a novel microalgae-based membrane bioreactor technology suitable for use in pump-and-treat groundwater treatment to effectively remove heavy metals in groundwater. The research objectives are divided into three parts: (1) to test the ability of different microalgae to remove heavy metals such as chromium, nickel, copper and lead in batch experiments. Experiments will be carried out to add different concentrations of heavy metals to the microalgae culture system to study the efficiency of heavy metal removal, adsorption kinetics, adsorption mechanism, microalgae growth, and other ions on heavy metal removal; (2) to culture the better microalgae in the ceramic membrane bioreactor and determine the efficiency of heavy metal removal. Microalgae with good removal rate of heavy metals selected by batch experiments will be cultured by membrane bioreactor with continuous feeding artificial and real heavy metal contaminated groundwater, to test the removal of heavy metals under different hydraulic retention time. In addition, the change of transmembrane pressure and the cleaning method for ceramic membrane fouling will also be studied; (3) to develop a continuous flow immobilized microalgae-membrane bioreactor system through the combination of membrane bioreactor and microalgae immobilization technology. The removal of heavy metals will be investigated for different hydraulic retention time and different amount of immobilized microalgae beads, and the effects of immobilized microalgae on changes of transmembrane pressure will also be investigated. We consider that the microalgae biomass produced after the treatment will have the potential for valorization and therefore, promoting the future heavy metal removal in groundwater in a circular economy way. According to the isothermal adsorption results of heavy metals in the three common microalgae, including Chlorella vulgaris, Scenedesmus quadricauda and Selenastrum capricornutum, the concentration of heavy metal nickel, copper and lead at 2.5 mg/L can be reduced within 1 hour. Only in the 96-hour adsorption experiment, it was found that the heavy metal adsorbed for a long time could be re-dissolved, and the nickel metal was more obvious. It was speculated that copper, nickel and lead were mainly through reversible adsorption, while chromium (Cr2O72-) showed the slower adsorption behavior than nickel, copper and lead likely due to the negative charge. Generally, the adsorption amount would be increased with time. We also observed the competitive behavior of mixed heavy metals absorption similar to the literature, and the competition was more obvious with copper and nickel. The functional groups on the cell surface played an important role in the adsorption of heavy metals. The increase in the concentration of microalgae could increase the total adsorption capacity and lower the equilibrium concentration, and the pH could affect the adsorption behavior of microalgae. The result of Langmuir fitting of thermoacidophilic red algae Galdieria partita was better than that of Freundlich. The results showed that Chlorella vulgaris, Scenedesmus quadricauda, Selenastrum capricornutum, thermoacidophilic red algae, immobilized materials and immobilized algae balls all had different degrees of heavy metal adsorption capacity. Both the external and immersed microalgae membrane bioreactors provided good heavy metal adsorption. The membrane also has the additional performance of maintaining stable effluent quality. The immersed microalgae membrane bioreactor was simple to operate, and the aeration could reduce its membrane fouling to maintain long-term operating flux. The actual groundwater passed through the microalgae membrane bioreactor, and more than 95% of the dissolved nickel could be removed in the tank. The system could reach 96-98% removal, and the dissolved nickel adsorption capacity was increased from 2 mg/g to 5.95 mg/ g. However, the removal rate of dissolved chromium decreased from 37% to the negative value over time. It is speculated that the increased chromium may be caused by the dissolution of reduced particulate precipitates or the slow absorption rate of algae to chromium. The water quality before and after system filtration was significantly improved. If the existing contaminated underground water treatment process is replaced by our system, the cost of the remediation can be reduced, and the feasibility of microalgae resource utilization can be evaluated after treatment. Overall, the system shows potential and advantages for future application.