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年度	110	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	教授
專案中文名稱	永續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	2,470,000元
執行期間	2021/2/24 至 2022/2/28
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。此外，為確定自製藥劑配方的成效，避免實驗室藥劑試驗成果與實場應用成效差異過大，致使藥劑未來應用於現地的可行性降低，故亦將透過現地模場試驗建立現地場址藥劑混合及灌注之標準作業程序。 本計畫為109至110年度兩年計畫，計畫共分為三階段，第一階段為製備最佳配比之自製乳化液(emulsified vegetable oils, EVO)及最合適之乳酸亞鐵添加比例。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液、脂肪酸酯及自製乳化液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，亦採用市售乳化液作為對照組別。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配比。 本計畫於109年度已完成第一階段及第二階段試驗，已成功製備最佳自製乳化液及最適合之乳酸亞鐵添加量，透過微生態模場試驗，於90天實驗時間內，自製乳化液添加乳酸亞鐵之三氯乙烯去除率可高達99%，其成效及降解速率皆高於市售乳化液，觀察到代謝產物順1,2-二氯乙烯濃度亦高於其他乳化液，且地下水中DCA1菌數亦由原本低於偵測極限，增加至6.17×103 gene copies/L。透過109年度第一階段及第二階段成果可知，自製乳化液結合乳酸亞鐵可取得較一般市售乳化液更佳的三氯乙烯去除速率及成效，且亦可降低自國外運送藥劑所產生之碳排放。 本年度(110年)計畫主要乃將透過現地模場注藥試驗，評估最佳配比自製乳化液及添加乳酸亞鐵應用於實場整治時之成效。鑒於本現地試驗模場屬於坋黏土與細砂互層之地質，使用重力灌注將無法有效將藥劑傳輸至不同質地含水層，本計畫改為採用雙封塞灌注工法進行藥劑灌注，透過馬歇管及雙封塞注藥泵，可針對含水層不同土壤質地，使用不同藥劑灌注壓力，達到藥劑可均勻擴散至污染含水層，避免產生整治盲區。台灣許多區域地質多屬沖積層且因位於環太平洋地震帶，因此台灣地質多以不同質地互層或夾層，雙封塞灌注工法之應用經驗，應可使國內土壤及地下水整治成功率提升。 試驗結果顯示，透過雙封塞藥劑灌注測試結果，模場區域地下水水位面以下地質狀況，4.5至6.5公尺間土壤質地較為細緻，7至12公尺間土壤質地通透性較佳，在固定灌注壓力2 bar情況下，6.5公尺以上藥劑灌注流量介於3.5-4.8 L/min，7至12公尺則為5-7.5 L/min。鑒於7-13公尺地質通透性較佳，污染物亦較容易於此深度傳輸，故模場藥劑灌注時將優先針對通透性較佳質地進行灌注。 模場試驗結果可知，透過微水試驗取得之場址水力傳導係數進行注藥量計算容易導致注藥量過低，使地下水中TOC濃度不足且無法擴散至預定整治目標區域。因此，建議未來場址整治皆可先透過抽水試驗或現地模場試驗，方可準確估算藥劑灌注量體。此外，由於批次藥劑灌注需於灌注井區域維持一定濃度，方可使下游目標區域之TOC維持穩定及上升趨勢，若灌注井區域TOC濃度低於一定限度，則下游目標整治區TOC可能尚未達到目標濃度便會開始降低。然而，單次藥劑量灌注較多，雖可延長再次灌注時間，但藥劑較容易尚未完全反應便往下游流失；單次藥劑量灌注較少，雖可減少藥劑損失，但灌注頻率卻會上升。因此，透過模場試驗及成本計算，亦可了解於該場址地質條件下，目標整治範圍其藥劑單次灌注量與灌注頻率之取捨。 本試驗成果顯示，距離灌注井1公尺處之監測井(觀測井1)，其含氯污染濃度雖最高，但因藥劑容易擴散至該區域且乳酸亞鐵充足情況下，TCE於試驗第88天便符合地下水管制標準且代謝產物皆無累積現象，至試驗後期，TCE及代謝產物皆低於偵測極限。距離灌注井3公尺處之監測井(觀測井2)，鑒於第一次藥劑灌注量不足，因此至試驗第200天其TCE方才符合地下水管制標準。觀測井2則可很明顯觀察到代謝產物累積且趨勢為當TCE降低時，cis-1,2-DCE濃度明顯上升；當cis-1,2-DCE濃度降低時，VC濃度則明顯上升。顯示觀測井2含氯污染物濃度降低主要應為厭氧還原脫氯機制，比較觀測井1及觀測井2兩者總鐵及亞鐵濃度變化，推測乳酸亞鐵擴散至觀測井2之量體應該有限。距離灌注井5公尺區域之監測井(觀測井3)，則於試驗第299天觀察到TCE低於管制標準，但代謝產物濃度則逐漸上升。由此可推測，自製乳化液可擴散傳輸距離至少可達5公尺，但乳酸亞鐵影響距離應僅限於2-3公尺之間。然而，乳酸亞鐵對於代謝產物還原效果顯著，因此未來應用部分可針對場址代謝產物容易累積之區域或採用現地生物整治場址之邊界，設置乳酸亞鐵透水性反應牆，可避免如VC等代謝產物因其傳輸速率較藥劑速率快，而擴散出場區範圍。模場試驗過程中不需灌注緩衝劑即可維持pH中性的狀態，也是因為乳酸亞鐵的功效。 自製研發的乳化液之成本僅為市售乳化油約二分之一價格，證實自製研發的乳化液藥劑之推廣將可提升國內含氯場址整治之成效。目前自製研發的乳化液主要以模場試驗規模生產，當擴展至實場規模乳化液的需求量時，必須保持乳化液的穩度性與質量，如此將有極佳的機會使產品商業化。
計畫英文摘要	This proposal combines in-situ chemical reduction and enhanced in-situ bioremediation to accelerate removal of trichloroethylene (TCE)-impacted groundwater. The combined remedies rapidly reduce the impacted groundwater into anaerobic condition by adding chemical reductant and supplement 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 and 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 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. The chemicals have good remedy efficiency; however, material transportation results in huge amount of carbon emission and they might not be 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 decrease carbon emission. This two-year project from 2020 to 2021 consists of three phases. Phase I is to develop an optimal combination ratio of emulsified vegetable oil (EVO) and most appropriate ratio of ferrous lactate additive. Phase II is to conduct microcosm test evaluating TCE degradation using the self-developed EVO, fatty acid ester, and self-developed EVO/ferrous lactate and comparing with a commercial EVO using groundwater and soil samples collected from a TCE-contaminated site. Phase III is to conduct 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. Phase I and II tests had been completed in 2020. It had been successfully developed the optimal combination ratio of EVO and most appropriate ratio of ferrous lactate. The TCE removal rate was 99% in 90 days after the addition of the self-developed EVO and additive ferrous lactate in a microcosm test. The effectiveness and degradation rate are higher than the commercial EVO. The product cis-1,2-DCE concentration was observed to be higher than other EVOs. The DCA1 bacterial count in groundwater increased to 6.17×103 gene copies/L from below detection limit. According to Phase I and II results in 2020, the combination of the self-developed EVO and ferrous lactate is more effective and has higher TCE removal rate than general commercial EVOs. It also reduces carbon emission resulting from transportation of chemicals from overseas. The best combination of self-developed EVO and ferrous lactate will be evaluated through in-situ chemical injection pilot test for the project in 2021. The originally planned gravity injection will not effectively deliver the chemicals to various geological aquifer due to the site geologic interlayer of silt, clay, and fine sand. The chemicals will be injected using double packer injection through Tube-a-Manchette and double packer injection pump. The chemicals will evenly spread to contaminated aquifer by use of various chemical injection pressure toward various lithology to avoid remediation blind areas. Most areas in Taiwan are alluvial lithology and located in Pacific Rim Seismic Belt, thus most geology is various geological interbed or interlayer. The application experience of double packer injection should increase the success rate of soil and groundwater remediation domestically. In addition, the standard operation procedures of in-situ chemical mixing and injection will be established through the in-situ pilot test to provide a reference for implementation of remediation at chlorinated solvent contaminated sites domestically. This is to ensure the effectiveness of chemical combination and to avoid huge difference between bench laboratory test results and field application effectiveness thus reducing the feasibility of future in-situ application of chemicals. The test through double packer chemical injection indicated the soil geological conditions below groundwater table is fine from 4.5 to 6.5 m and more permeable between 7 to 13 m in the pilot area. The injection flow was between 3.5 to 4.8 L/min for the soil above 6.5 m and between 5 to 7.5 L/min for 7 to 13 m interval under injection pressure of 2 bar. The chemical injection for the pilot test will focus on the more permeable 7 to 13 m soil because contaminants are easier to transport in the more permeable interval. The pilot test results indicated chemical injection based on the hydraulic conductivity from slug test could easily result in less amount so that TOC concentration in groundwater could not be distributed to the proposed remediation target area. Therefore, it is recommended to estimate chemical injection amount based on pumping test or pilot test. In addition, the batch chemical concentration should remain consistent in the injection area so that TOC concentration will remain steady and increase trend in the downgradient target area. The increase of chemical amount in each injection will prolong the next injection time, but the chemical could flow away without complete reaction. Lower chemical amount in each injection could reduce the loss of chemical but increase injection frequency. Therefore, the chemical amount and injection frequency should be balanced in each injection based on pilot test, cost estimate, and the geological and hydrogeological conditions of the site. The pilot test results indicated TCE concentration in Observation Well 1, which had the highest concentration of chlorinated contaminants and was located one meter away from the injection well, met groundwater control standard without accumulation of byproducts in 88 days because of easy chemical distribution in the area with sufficient amount of ferrous lactate. TCE and byproducts were below the detection limit later. TCE concentration in Observation Well 2, three meters away from the injection well, met the groundwater control standard in 200 days due to insufficient chemical amount. It is easy to observe byproducts accumulation and trend in Observation Well 2. When TCE concentration decreased, cis-1,2-DCE concentration increased. When cis-1,2-DCE concentration decreased, vinyl chloride concentration increased. This indicated the major mechanism to reduce chlorinated contaminants was anaerobic reductive dichlorination. It is hypothesized ferrous lactate distribution to Observation Well 2 was limited after the comparison of total iron and ferrous concentrations in Observation Wells 1 and 2. TCE concentration in Observation Well 3, five meters away from the injection well, was below the groundwater control standard in 299 days, but byproduct concentrations increased. It is hypothesized self-developed EVO could be transported to a distance at least 5 meters, but ferrous lactate only to a distance between two to three meters. However, ferrous lactate reduction of byproduct was significantly. Therefore, it could be applied to sites which are easy cumulation of byproducts or in-situ bioremediation site boundary. The installation of permeable reactive barrier could prevent byproduct such as vinyl chloride from migrating off the remediation area due to the quicker transport velocity than injection chemicals. During the pilot test, the neutral pH value can be maintained without introduction of buffers, which is also due to the effect of ferrous lactate. The self-developed EVO cost is just half of commercial EVO prices. It is advantageous to promote domestic EVO to help improve the remediation of chlorinated sites domestically. The self-developed EVO were mainly made in bench scale, the scale up of the self-developed EVO manufacture will be required to maintain the EVO quality and provides a great opportunity to commercialize the product.