好/厭氧環境整治工法於滯水層氣體分布調查技術研發

Abstract

生物整治為目前進行汙染場址整治常用之技術，於現地實施電極電解促進生物復育之整治方法為新穎之技術，其主要協助提供好氧厭氧環境以利好氧菌與厭氧菌對汙染物進行降解，達到破壞、轉化或移動、遲滯汙染物之整治目標。此工法相較於調查汙染物之降解程度，直接調查整治過程中之氣體產生之範圍，更可快速達到整治區域界定的方式。 經文獻回顧，以介電度量測氣體含量為高潛力之技術，有鑑於此，本研究利用具發展性之時域反射技術(TDR)系統分析方法，採用單棒式三叉感測器，訊號分析採用頻率域相位速度分析法，可快速、便捷且定量於監測井中進行量測氣體含量；並提出時序性之跨孔透地雷達於氣體含量調查之分析方法，透過孔內透地雷達觀察飽和土體內2維剖面之氣體含量變化。 室內試驗顯示，無論是TDR技術或是時序性跨孔透地雷達技術皆具有其可行性，TDR技術進行介電度量測具有定量調查水中氣體含量之潛力，而時序性之介電度變化可有效監測土體中氣體含量的變化。而現場資料顯示TDR量測時其感應範圍超過監測井(2”PVC管)進入回填材料範圍，此結果雖不利於定量量測，但可更加明確的顯示氣體存在的位置(根據現場氣體產生之工程師表示，監測井中不易存在氣體，反而回填砂之位置較為良好)；而時序性跨孔透地雷達之資料雖受限於電解試驗的失誤而未明確獲得氣體分布狀態的改變，但由此時序性資料亦可確實達到監測土體中氣體變化之目的。 關鍵字：跨孔透地雷達、時域反射法、氣泡量測

In-situ bio-remediation is the current practice of groundwater contamination treatment, while in-situ electrolysis conducted to enhance biological repopulation is amongst the new bio-remediation techniques. This bio-remediation method mainly assist in creating both aerobic and anaerobic environments to boost the growth of microorganisms and hence the pollutant disintegration. Efficiency of this treatment is better assessed by investigating the air bubbles distribution within the aquitard instead of determining the disintegration degree of pollutants, since the former method provided faster and extensive bio-remediation profile delineation and evaluation. Literature review revealed that dielectric constant measurement on multiphase material has high potential to measure the air concentration. This study hence designed an air content monitoring system involving time-domain reflectometry (TDR) technique, by developing a rod-shape probe with three conductor rods and utilizing frequency domain phase velocity (FDPV) analysis method. The aforementioned TDR method provided a quick and convenient qualitative air content measurement within monitoring wells. This study also proposed a time-lapsed cross-hole ground penetrating radar (GPR) in underground air content investigation and generated a two-dimensional profile of air content variation in saturated soils. Laboratory tests demonstrated that both TDR technique and time-lapse cross-hole GPR are feasible in air content monitoring. TDR technique had a great potential in air content quantification within water mass by dielectric constant measurement, while time-lapse TDR monitoring can effectively monitor air content variation within saturated soil mass. Field measurement data showed that the detection radius of TDR exceeded the diameter of the monitoring well casing (2 inches PVC tube) and detected the backfill material layer. Although the result of quantitative measurement is unfavorable, this method can actually identify the presence of air bubbles within backfill layer as one of the on-site engineer mentioned that air bubbles existed in backfill layer easier than within monitoring well. Whereas the air content distribution measurement of time-lapse cross-hole GPR was inconclusive due to a failure in electrolysis operation, however this set of time-lapse monitoring data has achieved the aim of air content variation monitoring in soil. Keyword: Cross-hole Ground Penetration Radar, Time Domain Reflectometer, Air Content Measuring