含氯有機物場址長時間整治所遭遇傳輸困難與因應改善之案例研究

本場址屬於大尺度含氯有機物（四氯乙烯與相關降解產物）污染場址，污染範圍超過23,000 m^2。場址含水層地質特性屬滲透性良好之礫石夾砂，但因整治區長期高頻率灌注（連續8年每週進行灌注）生物營養源，造成部分區域藥劑阻塞與生物膜屏障產生藥劑短流途徑，進而造成藥劑不易傳輸至目標監測井區域，以致污染物濃度回升或產生拖尾現象。本文討論整治場址常見短流現象及傳輸屏障問題，並提出因應改善作為。搭配新型灌注工法與地球物理即時分析技術評析兩處整治區整治成效。其中第一區（MW-05井區）之藥劑短流明顯，藥劑多沿地面溢流，應用「雙環塞滲透灌注工法」（double packer injection, DPI）進行多深度灌注，結合「跨孔式地電阻影像法」（cross-hole electrical resistivity tomography, CHERT）評估藥劑傳輸之優勢流徑與可能傳輸屏障區；第二區（MW-06井區）則是監測井與灌注井周遭因長期灌注糖蜜而被嚴重包覆（監測井洗井過程持續發現糖蜜混合液），本區應用「脈衝式雙環塞滲透灌注工法」（pulse DPI, PDPI），並結合「井內透地雷達法」（bore-hole ground penetrating radar, BGPR），評估藥劑傳輸分布是否改善。兩處整治區均證實應用之灌注工法可有效改善或突破目前之傳輸屏障，故擴大於其他七區（同樣遭遇傳輸困難區域）設置DPI或PDPI系統。各污染區經整治約2年期間，目前顯示各污染區均能克服原先短流與傳輸屏障問題，各項含氯有機物持續下降並符合管制標準。

關鍵字

傳輸屏障；精準整治；雙環塞滲透灌注工法；地物時間序列監測

並列摘要

The site under discussion here is a large-scale chlorinated volatile organic compound (CVOC) pollution site with perchloroethylene (PCE) and daughter products ranging over 23,000 m^2. The features of the aquifer include gravel and sand, which have high permeability. However, long-term, high-frequency injections of biological nutrients at the remedial zone (weekly injections continuing for 8 years) have generated reagent blocking and a biofilm barrier and have caused short-circuiting, which means these conditions make it more difficult for a reagent to transmit toward target monitoring wells, and the concentrations of the contaminants could rebound or trail. This essay provides a discussion of the common short-circuiting and transmission barriers in the remediation zone, and also proposes possible countermeasures. The team evaluates 2 remediation zones using new injection methods and real-time geophysical analysis technology. The first zone (MW-05) exhibits obvious short-circuiting conditions, where the injected reagent usually overflows along the ground surface. The second zone (MW-06) exhibits a severe blocking situation with the long-term molasses injected around the well (the molasses mixture continued to be drawn during the well flushing). In the first zone, the team applied a double packer injection (DPI) method for injections at multiple depths as well as cross-hole electrical resistivity tomography (CHERT) to evaluate the preferential flow of the reagent and the possible transmission barriers. In the second zone, the team applied a pulse DPI (PDPI) method using borehole ground penetrating radar (BGPR) to evaluate the distribution of the reagent transmission. Both of these remediation zones have proven that the current method could improve or break the transmission barrier effectively. Therefore, the team expanded the DPI and PDPI installation range into 7 other zones with the same transmission difficulties. Each pollution zone has conquered the original short-circuiting and transmission barrier after the 2 years of remediation, and the concentration of CVOC has decreased continually, thus meeting the control standard.

並列關鍵字

transmission barrier ； precise remediation ； double packer injection ； geophysical time series monitoring

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含氯有機物場址長時間整治所遭遇傳輸困難與因應改善之案例研究

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