現地透水性反應牆配置對含氯有機溶劑整治效率的影響

Abstract

本研究利用MODFLOW程式模擬地下水流，並配合RT3D模擬污染物之傳輸與降解反應。本研究以高雄楠梓加工出口區為例，模擬注入還原性或氧化性物質及不同形狀之現地反應牆配置。高雄楠梓加工出口區現存低濃度且範圍廣之含氯有機溶劑污染，且污染物已往楠梓加工出口區外移動中，土層狀況概分為六層，主要為砂土且導水度偏高，水文條件因後勁溪位於高雄楠梓加工出口區之東面及北面，故加工出口區內東部之地下水流向向東流，其他區域則為向北流，反應牆方面則設定在高雄楠梓加工出口區邊緣分為橫向及縱向配置觀察其差異。 研究結果顯示，現地反應牆配置的不同，對整治污染物有明顯的差異。因為氧化劑或還原劑在土層中需要反應的時間，而反應牆通常會搭配置換土壤，換成導水度較高的土壤方便控制水流使污染物通過，但也會使的污染物經過反應牆時停留的時間不夠長，故若使用還原性物質(例如：零價鐵)時，因其反應速率較低，使其降解不及於反應牆中反應完全，造成降解產生出的氯乙烯有超標的現象，故設計反應牆的形狀便顯得很重要。 經過比較結果，零價鐵透水性反應牆使用細長型配置時，會使汙染物的流經路徑變長，污染物有效的降低濃度，三氯乙烯、二氯乙烯幾乎全部消失，原本會過量的氯乙烯也都控制在管制標準以下，而使用過錳酸鉀透水性反應牆時，因其反應速率非常高，故設計上只要攔截的到污染物就可整治完全，故設計橫向配置 之反應牆其整治成效較佳。

This research studied the migration and degradation of chlorinated solvent plume in aquifer by simulation with MODFLOW and RT3D. The DNAPL site Nantze Export Zone in Taiwan Kaohsiung was chosen as the site for the case study. Remediation by injecting reducing or oxidizing agents into permeable reactive zone of variable shape and size was simulated. Groundwater in the aquifer beneath the Kaohsiung Nantze Export Zone is contaminated with chlorinated solvents and the plume was moving across the boundary towards Houjin Creek in the north. The hypothesized permeable reactive zone is located near the northern boundary of Nantze Export Zone and various configurations were simulated to study the effect on remediation efficiency. The results show that the variation of permeable reactive zone configuration lead to difference in the reaction time and, in turn, the remediation efficiency. Highly permeable reaction zone can effectively guide the groundwater flow through it but the tradeoff is the short reaction time which is not long enough for significant reductive degradation of pollutants. As a result, the concentration of vinyl chloride which had been produced by reductive degradation would exceed regulation limit. On the other hand, chemical oxidation in permeable reactive zone may destruct chlorinated solvents in the permeable reaction zone more effectively as demonstrated by the simulation. The results of the research show that, the Zero-Valent Iron of permeable reactive zone using elongated configuration makes the flow path longer, and reduces the concentration of pollutants. The TCE and DCE are almost disappeared. The Potassium Permanganate of permeable reactive zone using lateral configuration can intercept pollutants more effectively.