不同長效釋氧化合物物化特性與實地應用之探討

Abstract

本研究主要探討應用於土壤及地下水生物復育之釋氧化合物，如：EOx™與PermeOx®Plus，藉由批次試驗與連續試驗方式模擬現地改善模式與操作條件，並觀察基本水質變化與評估其應用條件。 在批次試驗中所使用之去氧水，係參考文獻中提及之兩種去氧方式，如氮氣曝氣與Na2SO3去氧，以氮氣曝氣方式可於短時間內去除水中溶氧量，且對於基本質影響較小，故做為後續試驗之基底用水。本試驗另透過短時間尺度與長時間尺度觀察釋氧化合物溶水後其水質變化，依實驗結果得知，PermeOx®Plus溶解效率較佳，可於短時間內提高水中溶氧量，溶氧量約可至14 mg/L，而EOx™之溶氧量約至12 mg/L，藉由透過文獻得知，釋氧化合物可因添加不同種類與濃度之緩衝物質，除可緩衝CaO2造成pH濃度上升外，加速CaO2釋氧反應，提高或延長釋氧化合物之供氧效果，因此，推估PermeOx®Plus可能添加類似物質；另外，藉由過濾方式去除釋氧化合物粉末（基質），發現水中溶氧已無持續提升，推估釋氧化合物成分中所含CaO2經水解後釋放Ca(OH)2和H2O2，其中H2O2具有提高水中溶氧之效果；最後，透過採取兩處污染場址之背景土壤與釋氧化合物過濾後取得之含氧水反應，以及選用曝氣後取得之含氧水做為對照組，依實驗結果，土壤氧氣消耗率約0.0079~0.20 mgO2/day/g-soil，而釋氧化合物產生之含氧水與曝氣後之含氧水對於本階段試驗土壤氧氣消耗率差異不大。 在管柱試驗中，因考量釋氧化合物可應用於不同污染改善工法，以及可能受不同場址背景條件影響，故藉由本試驗改變不同填充型態操作方式與調整管柱流速，評估釋氧化合物實地應用。本試驗以3種不同填充型態進行比較，發現散狀填充方式具有較佳供氧效果，其次是餅狀填充及球狀填充，由上述結果，推測釋氧化合物與水之有效接觸面積可直接影響釋氧效果；另EOx™與PermeOx®Plus以散狀與餅狀填充方式進行比較，仍可發現散狀填充之供氧效果較佳，但對於EOx™與PermeOx®Plus之水中溶氧表現已無明顯差距，故推估2種釋氧化合物應用於離地改善工法（土耕法、排土客土法）時，釋氧效果差異不大。次試驗則於不同流速下進行釋氧化合物試驗，依實驗結果，DO濃度高低隨著流速提高而減少，推估可能為CaO2與水反應時間縮短，使釋氧效果逐漸降低；依EOx™試驗結果，管柱流速設定於4 ml/min及10 ml/min時，測得DO濃度差異不大，約5 mg/L，惟流速1 ml/min可測得DO濃度約6~7 mg/L；反之，PermeOx®Plus依流速遞減 （10 ml/min、4 ml/min、1 ml/min），DO濃度有增加現象，DO值平均最高濃度約8 mg/L，但隨著水力停留時間增加，PermeOx®Plus之釋氧量相對降低。綜合本研究結果， PermeOx®Plus在各試驗表現上，具有水解效果較佳且於初期釋氧效果快速，而EOx™可穩定提供水中溶氧且具有較長之釋氧效期。

The purposes of this research are to study biological remediation in soil and groundwater with oxygen-releasing compounds, such as EOx™ and PermeOx®Plus. The study is to simulate field models and operating conditions through batch test and continuous test, to observe basic water quality changes and evaluate its application conditions. In the batch test, this test removes oxygen in water by nitrogen aeration and Na2SO3. Nitrogen aeration can remove dissolved oxygen in water for a short time and has no effect on basic quality changes, so it is used as the water supply source for the next test to use. Oxygen-releasing compounds are mixed with low-oxygen water to observe water quality changes through short time scales and long time scales. According to the results, after mixing for about 40 minutes, the dissolved oxygen content of PermeOx®Plus can reach about 14 mg/L, and the dissolved oxygen content of EOx ™ can reach about 12 mg/L. In the literature, CaO2 can be mixed with different kinds of buffer substances to accelerate oxygen release. Therefore, maybe the PermeOx®Plus was added the different buffer substance to make the oxygen release effect better. PermeOx®Plus can increase the dissolved oxygen in a short time, which has better dissolution efficiency. In addition, when using the 0.45 μm filter to remove the oxygen-releasing compound powder, the dissolved oxygen has not been continuously increased. Thus, the CaO2 in the oxygen-releasing compound powder was the main source of oxygen release. In addition, we took the background soils of two sites to mix with filtered oxygen-release compounds and saturated aerated water. It was found that the oxygen uptake rate was between 0.0079 to 0.20 mg O2/day/g-soil. In the column test, we change the filling types and flow rate with reference to the application of pollution remediation methods and background condition of different sites, to evaluate the field application of oxygen-releasing compounds. In the first test, we compared the three different filling types to evaluate oxygen release efficiency of oxygen-releasing compound, such as bulk filling, pie filling and spherical filling. In the experimental results, the bulk filling method has a better oxygen supply effect, followed by pie filling and spherical filling. From the above results, it is estimated that the effective contact area of the oxygen-releasing compound can directly affect the oxygen-releasing effect. In addition, when EOx ™ and PermeOx® Plus are compared in the form of bulk filling and pie filling, it can be sure the effect of bluk filling is better, but is not much different between EOx™ and PermeOx®Plus. Therefore, it is estimated that the oxygen release effect of EOx ™ and PermeOx®Plus will be similar as applied in land farming and excavation. Furthermore, oxygen-releasing compounds were tested at different flow rates. According to the experimental results, the oxygen release efficiency of the oxygen-releasing compounds is relatively reduced as the flow rate increases, likelydue to the reduced contact time between with CaO2 and water. According to the EOx ™ test results, when the column flow rate is set to 4 ml / min and 10 ml / min, the measured DO concentration is similar (5 mg/L), but the measured DO concentration is about 6 to 7 mg / L at the flow rate of 1 ml / min. Conversely, for the PermeOx®Plus, the DO concentration increases when the flow rate decreases. The average maximum DO value is about 8 mg/L. Therefore, PermeOx®Plus has a better oxygen release effect, while EOx™ has provided longer oxygen supply time.