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年度	109	專案性質	實驗性質
專案類別	模場試驗	研究主題	整治
申請機構	朝陽科技大學	申請系所	環境工程與管理系
專案主持人	劉敏信	職等/職稱	副教授
專案中文名稱	以現地化學還原法結合生物整治法降解地下水三氯乙烯污染物
中文關鍵字	乳酸亞鐵,現地化學還原法,生物整治法,三氯乙烯,綠色永續整治
專案英文名稱	Sustainable In-Situ Chemical Reduction and Enhanced In-Situ Bioremediation Combined Remedies to Accelerate Treatment of TCE-Contaminated Groundwater
英文關鍵字	Ferrous lactate, In-situ chemical reduction, Bioremediation, Trichloroethylene, Green and sustainable remediation
執行金額	1,980,000元
執行期間	2020/1/1 至 2021/12/31
計畫中文摘要	本計畫結合現地化學還原法及生物整治法加速去除地下水中三氯乙烯污染物，透過添加還原試劑於地下環境中，將水質迅速轉變為厭氧狀態，同時輔以自製的乳化液作為緩釋型之釋氫基質供微生物利用。本計畫以乳酸亞鐵作為還原試劑，乳酸亞鐵可提供微生物所需的碳源以快速啟動後續生物整治機制，亦可作為氧去除劑用於去除水體中殘留的溶氧，並將水質保持在較低的氧化還原電位，為厭氧菌營造其適合的環境。乳酸亞鐵中含有亞鐵(Fe2+)，該亞鐵可形成多種鐵礦物質，當它們進一步氧化成為三價鐵(Fe3+)時則能夠還原三氯乙烯為乙烯，透過電子轉移，只要原污染場址所擁有的碳源或添加乳化液為碳源提供電子所用，其三價鐵離子即可再次還原為亞鐵，透過此循環則可將三氯乙烯以更快的速率去除。與此同時亦透過注入乳化液作為緩釋型的釋氫基質，提供電子讓地下微生物可進行長時間的生物性厭氧還原脫氯過程，將生物及非生物性的厭氧還原脫氯同時應用於整治三氯乙烯上，達到良好之污染物降解成效。 台灣目前應用於含氯污染場址之商用生物營養鹽藥劑多自國外購入，雖有良好之整治成效，惟以綠色整治之觀點，藥劑的運輸亦造成大量之碳排放且不一定較適合台灣氣候及土壤質地。因此，研發國產生物營養藥劑不但可因應場址特性進行調整且亦可減少碳排放。 本計畫共分為三階段，第一階段為製備兩種不同乳化液(emulsified vegetable oils, EVO)，一種為自製乳化油，透過不同乳化劑組合試驗、食用油/乳化劑配比試驗來找尋自製乳化油最佳配方，本試驗自製乳化油食用油所使用之比例是高於一般市售乳化油；另一種為脂肪酸酯，透過乳酸乙酯及油酸比例變更，尋找最穩定之脂肪酸酯乳化液，脂肪酸酯可縮短乳化油注入後環境達到穩定所需時間，而且可以避免乳化油所造成的井垢。同時評估市售乳酸亞鐵其還原三氯乙烯最合適之添加比例。 第二階段則利用某場址現地地下水及土壤建立Microcosm微生態模場試驗，評估第一階段最佳比例之自製乳化油、脂肪酸酯及自製乳化油結合乳酸亞鐵三種不同乳化液對三氯乙烯降解成效之差異。同時，亦採用市售乳化油(EOS)作為對照組別。 第三階段則使用第二階段試驗成果中效果最佳之乳化液進行實場之現地生物模場試驗，該場址將透過1口灌注井及3口觀測井，評估最佳乳化液應用於實場上之成效，同時建立乳化液灌注程序，透過現地模場試驗之成果再次優化乳化液之成分。 目前已完成第一階段試驗，第一種乳化液自製乳化油最佳配比為食用油配合Simple Green及脂肪酸蔗糖酯之複合型乳化劑，三者比例分別為69.5%、10.5%及4.5%。自製乳化油於前述比例情況下，混合原液可穩定保持至少一週以上不分層，模擬藥劑灌入地下水後之狀態，將藥劑稀釋10倍至20倍，仍可維持72小時後方才產生破乳，形成油水分層狀況，優於市售EOS稀釋20倍48小時後便破乳。第二種乳化液脂肪酸酯最佳比例為油酸10.4%、甘油5%、乳酸乙酯5.9%、緩衝溶液1%、水77.7%情況下可得到48小時內階穩定之脂肪酸酯乳化液。 添加不同體積比之乳酸亞鐵(0.5%、1%、2%)試驗結果可知，乳酸亞鐵隨添加體積比增加，亦使地下水ORP及DO更容易達到還原狀態，然而添加過多的乳酸亞鐵亦容易使地下水pH偏低。乳酸亞鐵添加體積比於2%以內，pH雖仍可維持在5.5以上，然而對照1%與2%還原三氯乙烯成果可知，添加1%乳酸亞鐵於第10天時，TCE降解成效約29%，相較於2%其TCE降解成效27.5%差異不大，考量成本及pH影響，後續第二階段試驗之乳酸亞鐵添加將以1%為基準。 本期報告已完成第二階段微生態試驗模場(Microcosm)，包括空白組(無任何營養鹽) 、自製乳化液組、自製脂肪酸酯組、市售EOS組以及自製乳化油加上1%乳酸亞鐵組，每組皆製備第0天、25天、45天、65天及90天之血清瓶樣品，分別於開始試驗後之對應天數進行開瓶分析水質。不同種類組別皆固定添加15 mL之藥劑量及適量之營養鹽。 微生態模場試驗結果顯示，自製乳化油+乳酸亞鐵之組合可使ORP及DO較其他組別更快降低，達到穩定之還原態，但因添加乳酸亞鐵，其pH值亦為所有藥劑種類中最低，後續第三階段現地模場試驗若有相同情況發生，可透過磷酸氫二鈉等緩衝劑添加，藉以調整pH值。 不同藥劑組別對於TCE降解成效以自製乳化油+乳酸亞鐵成效及速率最快，於第45天開始，TCE便達到99.8%之去除率，而自製乳化油則於第90天方達到98.9%之TCE去除率，油此推測添加乳酸亞鐵可加速微生態模場試驗環境形成穩定還原態，進而加速TCE降解速率。市售EOS於試驗結束後，最高TCE去除率可達87.5%，對照其第90天之TOC濃度仍有約2,500 mg/L，顯示若延長試驗時間，EOS應亦可達到95%以上之移除率。推測自製乳化油因其含油量較高，故TCE降解速率略高於市售EOS藥劑。 各藥劑組別皆無觀察到VC產生，但對照自製乳化油+乳酸亞鐵其順1,2二氯乙烯濃度為各組最高且qPCR分析結果顯示DCA1菌數由原本低於偵測極限，增加至6.17103 gene copies/L，顯示若延長微生態模場試驗，自製乳化油+乳酸亞鐵該組預計可觀察到VC產生。 第三階段選擇使用自製乳化油+乳酸亞鐵之藥劑進行現地生物模場試驗，考量選擇的場址地質為坋、黏土與細砂質地互層，故藥劑灌注方式將採用雙封塞低壓滲透灌注工法進行。雙封塞灌注井主要是由馬歇管、皂土水泥漿所構成，藥劑灌注時則使用雙封塞灌注系統進行。目前已完成現地生物模場試驗1口雙封塞灌注井及3口觀測井設置作業，並進行背景水質採樣分析，後續將進行藥劑灌注及定期監測作業，以評估自製乳化油+乳酸亞鐵應用於場址可行性。
計畫英文摘要	This project combines in-situ chemical reduction and enhanced in-situ bioremediation to accelerate removal of trichloroethylene (TCE)-impacted groundwater. The combined remedies rapidly transfer the impacted groundwater into reductive anaerobic conditions by adding chemical reductant and supplementing oil emulsion used as hydrogen release agent for anaerobic microorganisms. In this study, ferrous lactate was selected as the chemical reductant. Ferrous lactate can provide carbon source required by microorganisms to jump start the biological remediation mechanism. It can also be used as oxygen scavenger to maintain low redox potential that creates favorable environments for anaerobic bioremediation. The soluble organo-iron compound comprised of ferrous iron (Fe2+) can form a variety of iron minerals which are capable of reducing TCE into ethylene through chemical reduction and being oxidized to ferric iron (Fe3+). The ferric iron can be reduced back to ferrous iron through bioremediation as long as electrons from supplied carbon, such as oil emulsion, or indigenous carbon are available. Through this sustainable cycle, TCE removal can be accelerated through chemical reduction and biodegradation mechanisms. Oil emulsion is injected as slow release hydrogen source to supply electrons for microorganisms to sustain a long-term biological anaerobic reductive dechlorination process. Both abiotic and biotic anaerobic reductive dechlorination are applied to the treatment of chlorinated solvent and achieve better degradation results as green and sustainable combined remedies. The current substrates and bio-nutrients applied to chlorinated solvents contaminated sites in Taiwan are mostly purchased from overseas. They have good remedy efficiency; however, material transportation results in huge carbon emission and might not suited for the special climate and soil geology in Taiwan from green remediation perspective. Therefore, a research and development of domestic substrates and bio-nutrients is not only suited for specific site characteristics but also for carbon emission reduction. The project is divided into three phases. Phase I is a development of two different emulsified vegetable oils (EVOs). One is an EVO using different mixing ratio of soy bean oil and surfactant to maximize soy bean oil percentage in the EVO. The EVO is developed to have higher oil percentage than the commercial products. The other is a fatty acid ester using different mixing ratio of oleic acid and ethyl lactate to stabilize the solution especially under high TDS conditions. The fatty acid ester is developed to minimize scum generated by regular EVO injection. In the meantime, ferrous lactate was added optimally to enhance chemical reduction of trichloroethylene (TCE). Phase II is a microcosm test to evaluate TCE degradation comparing the self-developed EVO, fatty acid ester, and self-developed EVO/ferrous lactate with a commercial EVO such as EOS in groundwater and soil samples collected from a TCE-contaminated site. Phase III is a pilot test using the best performance EVO set from Phase II microcosm test results. An injection well and three observation wells will be used to evaluate the field-scale implementation performance and establish the injection procedures to optimize the EVO ingredient. Currently Phase I test has been completed. The self-developed EVO consists of soybean oil (69.5%), Simple Green surfactant (10.5%) and fatty acid sucrose ester (4.5%). The 10 to 20 times dilution of self-developed EVO will be demulsified 72 hours after a simulation injection test into groundwater, which is better than the 20 times dilution of commercial EOS demulsified after 48 hours. The fatty acid ester consists of oleic acid (10.4%), glycerin (5%), ethyl lactate (5.9%), buffer (1%), and water (77.7%) to stabilize the solution. Addition of different ratio of ferrous lactate (0.5%, 1%, and 2%) indicated higher percentage was easier to reach reduced conditions of ORP and DO but with lower pH. The pH sustained above 5.5 if ferrous lactate addition was less than 2%. TCE degradation rate was about 29% at 10 days after adding 1% ferrous lactate comparing with 27.5% TCE degradation for 2% ferrous lactate. Because TCE degradation is not much difference for 1% or 2% ferrous lactate, Phase II test will use 1% ferrous lactate considering chemical cost and pH effect. Phase II microcosm test has been completed including a blank (without nutrients), self-developed EVO, fatty acid ester, self-developed EVO/ferrous lactate (1%), and commercial EOS. Each set was added 15 mL dosage and appropriate nutrients and water samples were collected and analyzed water samples at 0, 25, 45, 65, and 90 days. The microcosm test results indicated the self-developed EVO/ferrous lactate set was faster than the other sets to lower down ORP and DO to achieve stable reductive conditions. However, pH was the lowest among the sets due to the addition of ferrous lactate. If low pH occurred during Phase III pilot test, a buffer such as sodium hydrogen phosphate will be added for pH adjustment. The self-developed EVO/ferrous lactate set had the highest TCE degradation rate among the sets. Its TCE degradation rate was 99.8% at 45 days, and self-developed EVO set reached 98.9% degradation rate at 90 days. This indicated the addition of ferrous lactate accelerated the favorable reduced environments and TCE degradation rate. The commercial EOS reached the highest TCE degradation rate of 87.5% at 90 days with remaining TOC of 2,500 mg/L, which indicated EOS could reach more than 95% TCE degradation rate if the test was extended. The self-developed EVO has higher organic content than the commercial EOS. Theoretically the TCE degradation will be higher too. VC was not detected in each set. However, the highest cis 1,2-DCE concentration was detected in the self-developed EVO/ferrous lactate set. In addition, DCA1 microbes increased to 6.17 x 103 gene copies/L from below the detection limit, which indicated VC could be detected in the set if the test was extended. The self-developed EVO/ferrous lactate will be selected for Phase III pilot test. The chemicals will be injected using double packer low pressure injection due to the site geologic interlayer of silt, clay, and fine sand. Double packer injection wells are constituted of Tube-a-Manchette and cement bentonite slurry. Currently, a double packer injection well and three observation wells have been installed, and background groundwater samples have been collected and analyzed for characterization. The next step will be chemical injection and periodic groundwater monitoring to evaluate the feasible application of self-developed EVO/ferrous lactate at the site.