臭氧注氣法處理飽和層及未飽和層柴油污染物試驗

Using Ozone Sparging to Degrade Diesel Contaminant in Saturated and Vadose Zones

張玲禎(LING-ZHEN ZHANG)

指導教授 ： 張迪惠 ； 劉敏信

朝陽科技大學/理工學院/環境工程與管理系/碩士(2018年)

摘要

柴油污染場址因物質的低揮發特性，整治工法難以物理方式執行，如飽和層使用的空氣注入法(Air sparging, AS)，以及適合未飽和層的土壤氣體抽除法(Soil vapor extraction, SVE)。因此化學氧化法較能快速有效率的降解柴油污染物，但以現地整治方式，對於未飽和層液體氧化劑在添加注入時，常會因優勢流或短流現象，以及接觸氧化反應的非均勻性，無法有效的完全去除柴油污染物。而化學氧化法中使用的臭氧氣體，可以針對飽和層地下水中柴油污染物降解去除，也較能充滿在未飽和層土壤孔隙之間，增加臭氧氧化污染物的機率。雖然臭氧氧化處理費用較液體氧化劑昂貴，但具有同時處理飽和層及未飽和層柴油污染物的效果，因此在現地整治工法中，不失一個良好的選擇。
本研究目前製備飽和層及未飽和層同時污染柴油的小型模場，利用臭氧注氣法(Ozone sparging)方式探討化學氧化能力。研究初始以連續式臭氧注氣系統探討降解成效與最佳操作條件，結果顯示當空氣流量設定為10 L/min時，可得到最佳化臭氧產率2,888 mg/min。依柴油降解效率選擇每批次1小時臭氧注氣方式，進行多批次試驗同時處理飽和層及未飽和層中之柴油污染物。當處理含柴油污染濃度4,100 mg/kg土壤時，注入臭氧第4小時後土壤柴油濃度即可低於土壤污染管制標準1,000 mg/kg以下，但仍有柴油殘餘濃度約600-700 mg/kg難以氧化降解，大部分屬於高碳數或支鏈碳氫化合物組成。隨著離臭氧注氣井篩距離半徑越遠時，降解效率也明顯降低，當以臭氧氧化含柴油污染濃度24,200 mg/kg土壤時，此現象越為明顯。當以臭氧注氣方式處理含柴油污染濃度300 mg/L地下水時，注入臭氧1小時後地下水柴油濃度即可低於地下水污染管制標準10 mg/L，柴油降解效率可達95%以上。臭氧注氣系統的空氣流量5-18 L/min所產生之臭氧尾氣濃度皆能低於空氣品質標準0.06 ppm，並不會造成人體健康影響及空氣污染。研究結果亦顯示，模場的毛細管層相較飽和層及通氣層的鐵片鏽蝕情形最為顯著，顯示接觸臭氧的時間較長越容易造成鏽蝕現象。

關鍵字

氫氧自由基 ； 臭氧注氣法 ； 總石油碳氫化合物 ； 臭氧尾氣

並列摘要

With characteristics of its low volatility¸ the diesel contaminated sites suggest poor results of using physical approaches such as Air Sparging (AS) for saturated zones or Soil Vapor Extraction (SVE) for vadose zones. Therefore, chemical oxidation has being widely utilized to serve as an effective and efficient tool to degrade diesel pollutants. Nevertheless, some in-situ practices like complementing liquidized oxidants as dosage shows unsatisfied results due to its prevailing, short-cut flow or inhomogeneous contact between oxidants and target pollutants in vadose zones. The application of ozone, as one of the chemical oxidation measures, could aim at removal of diesel contaminant in saturated zone, and its relatively high mobility in vadose zone also contributes the possibility of oxidizing the contaminants. The ozone application can simultaneously remove diesel contaminants either at saturated or vadose zones shall be a feasible undertaking even it is expansive compared with other in-situ alternatives.

A pilot plant featured both saturated and vadose zones contaminated by diesel was prepared for the study. Application of ozone sparging was then introduced to investigate the performance of oxidation. Firstly, the best degradation and optimum parameters of operation by conducting continuous ozone sparging was determined, the best ozone yield rate 2,888 mg/min was obtained while using air flow rate at 10 mL/min in this study instrument. The experiment was then using one hour per batch ozone sparging to remove diesel from saturated or vadose zones. The contaminated soil, with diesel concentration 4,100 mg/kg, could be degraded by ozone sparging to below 1,000 mg/kg which is the soil pollution control standard for diesel in Taiwan. However, the residual diesel with concentration 600-700 mg/kg was difficult to degrade, those was identified as high molecular and branch chain petroleum hydrocarbons, this phenomenon was obvious in longer distance from ozone sparging screen and high diesel concentration 24,200 mg/kg was selected in the experiment. Using ozone sparging for one hour to degrade contaminated groundwater with 300 mg/L diesel, the removal efficiency could reach 95% above, and the diesel concentration could be below 10 mg/L which is the groundwater pollution control standard in Taiwan. The ozone sparging system was operated with air flow rate between 5 to 18 L/min, the off-gas ozone was determined to be below air quality standard 0.06 ppm. In addition, corrosion was observed in capillary layer due to longer contact time with ozone.

並列關鍵字

Hydroxyl radical ； Ozone sparging ； Total petroleum hydrocarbons ； Off-gas ozone

參考文獻

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