醇類增加輕質非水相液體揮發應用於整治受柴油污染地下水之可行性研究

Volatilization Enhancement of LNAPLs through the Addition of Alcohol to the Remediation of Diesel-oil-contaminated Groundwater

吳怡慧(YI-HUI WU)

指導教授 ： 趙煥平

中原大學/工學院/環境工程學系/碩士(2017年)

https://doi.org/10.6840/cycu201700583

摘要

空氣注入法配合土壤蒸氣萃取為常見且行之有年的土壤地下水整治技術，具有設備建置容易及成本低廉等優勢，然而這項整治技術受到污染物揮發性的限制，常見揮發性較低的污染物如柴油、煤油等物質，將使得整治期程拉長或整治效果不彰，因此本研究應用醇類增加水中有機物揮發的性質，加強空氣注入法配合土壤蒸氣萃取對於柴油污染物的整治效果。
本研究以模場模擬空氣注入法配合土壤蒸氣萃取進行實驗，模場實驗的時間依據污染物揮發性不同在1至48小時之間。實驗過程中以市售活性碳採樣管柱吸附揮發出的有機物蒸氣，參照標準方法以溶劑萃取活性碳之後，以氣相色層分析儀分析實驗結果，實驗條件將以加入不同碳數及濃度的醇類、不同有機質的土壤進行分析比較。醇類增加有機物揮發延伸至共揮發理論，根據共揮發理論的研究結果，本研究選用正戊醇、正己醇、正庚醇三種醇類，以醇類濃度5、10 ppmv進行實驗，檢視醇類碳數增加及濃度增加，對於污染物揮發增加的效果；另外一項實驗條件則為加入不同有機質的土壤，根據研究土壤有機質會吸附有機物蒸氣造成揮發抑制，因此本研究以不同有機質的土壤進行實驗，評估有機質高低的影響。而污染物則分為兩個部分，第一部分為柴油組成的個別有機物，使用含碳數C9至C14的直鏈烷類；第二部分則使用市售柴油進行研究。
研究結果顯示，由於柴油及其組成之單一化合物會於液面上方形成輕質非水相液體，低濃度的醇類於水中吸引有機物往氣液交界面移動的作用力，並未對液面上方高濃度的輕質非水相液體造成顯著影響，有機物揮發未隨醇類濃度增加以及碳數不同有明顯變化的趨勢。此外因為輕質非水相液體受曝氣擾動而移動，各批次實驗受到的擾動強度不同，揮發結果並未相當穩定。柴油及其組成之化合物揮發質量未呈現隨土壤有機質含量提高而遞減的明顯趨勢，主因來自於高有機質土壤因為模場實驗曝氣、水含量增加產生龜裂的情形，土壤龜裂形成的優先流道使得有機物蒸氣直接穿過優先流道，而未穿過土壤受到土壤中有機質吸附，使得土壤對於揮發質量削減未呈現穩定。
整體而言，本研究模擬實際整治狀況受限於設備無法完整呈現實際整治場址的狀況，污染物未受土壤介質及模場空間限制而移動、土壤水含量增加形成優先流道，為造成實驗未呈現穩定的因素，在實際整治中也會面臨污染物受曝氣擾動導致污染範圍擴大的問題，規劃模場設備除了考慮現地整治所面臨的的環境之外，也必須考慮模場結構對於污染物的適用性。

關鍵字

醇類 ； 共揮發 ； 柴油 ； 空氣注入法 ； 土壤蒸氣萃取

並列摘要

Air sparging combined with soil vapor extraction(AS/SVE) is a common technology for remediation of soil and groundwater contamination. There are some advantages of this technology, such as easy equipment installation and low cost. However, AS/SVE may not be suitable or effective for removing the pollutants with low volatility. It would take longer treatment schedule and higher cost. Therefore, in this study, a method was developed to enhance volatilization of LNAPLs through adding alcohol to remediate diesel-oil-contaminated groundwater. According to the co-volatilization theory, the higher concentration and the higher carbon ranges of alcohol causes more volatility of organic compounds. In addition, a number of researches indicated soil organic matter content would adsorb organic vapor and reduce the volatilization from AS/SVE system. The influence of above-mentioned conditions would be examined.
In this study, a 3-D model was equipped to simulate AS/SVE remedial technology. The experiment period was set from 1 to 48 hours based on the volatility of each chemical. The organic vapor was adsorbed by a commercial activated carbon tube. After experiment, the sorbent was extracted, and the sample was analyzed by gas chromatography. Three kinds of alcohol, n-pentanol, n-hexanol and n-heptanol, were selected to implement the experiments. The concentration of alcohol was 5 and 10 ppmv. Moreover, two kinds of soil with different organic matter content were used to examine the result. The target chemicals were alkanes with carbon ranges C9 to C14 and diesel fuel.
The results demonstrated the components of diesel fuel formed LNAPLs, floated on water table, were not affected by the addition of alcohol with low concentration in system. The volatility of LNAPLs didn’t be enhanced with the increasing concentration and carbon ranges of alcohol. The results were not stable since the migration of LNAPLs in 3-D model and the effect on volatilization by residual chemical from last batch. The volatilization inhibition of LNAPLs by the soil with high organic matter content was not significant. It resulted from the preferential flow caused by the crack of soil.

並列關鍵字

alcohol ； co-volatilization ； diesel fuel ； air sparging ； soil vapor extraction

參考文獻

[1] 土壤及地下水污染整治法, 2000.

[7] 童科憲, "利用醇類配合空氣注入法復育受有機物污染地下水之研究," 碩士論文, 生物環境工程研究所, 中原大學, 桃園市, 2016.

[17] 蕭松旺, "醇類對水中有機溶質揮發影響之研究," 碩士論文, 土木工程研究所, 中原大學, 桃園市, 2011.

[80] 陳仁炫, 蔡蕙芳, 林毓雯. (2004). 三種分析方法在測定肥料中有機質含量之適宜性評估. pp.116-124.

[8] W. Weisman, "Total Petroleum Hydrocarbon Criteria Working Group series: Volume 1: Analysis of petroleum hydrocarbons in environmental media," Amherst Scientific Publishers, Amherst, MA1998.