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首页> 外文会议>2003 Petroleum hydrocarbons and organic chemicals in ground water: prevention, assessment, and remediation >Challenges for the Application of In-Situ Chemical Oxidation in a Complex Glacial TillAquifer with Steep Hydraulic Gradients
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Challenges for the Application of In-Situ Chemical Oxidation in a Complex Glacial TillAquifer with Steep Hydraulic Gradients

机译：在具有陡峭水力梯度的复杂冰川Till含水层中原位化学氧化应用的挑战

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In-situ chemical oxidation (ISCO) using Fenton's Reagent (hydrogen peroxide and ferrous sulfate) was appliedrnas a removal action to address a release from a former underground petroleum storage tank at a closed NavalrnFacility in Massachusetts. The failure of this technology to meet treatment goals has unique implicationsrnregarding the challenges of applying ISCO to complex sites.rnThe petroleum release occurred in a sandy glacial till unit (hydraulic conductivity of approximately 3.2 × 10-rn4cm/sec) at the top of a steep hill, and the contaminants formed a narrow groundwater plume headed offpropertyrntoward wetlands approximately 700 feet downgradient. The contaminants of concern includedrnbenzene, toluene, ethylbenzene, xylenes (BTEX), naphthalene, and 2-methylnaphthalene, with a maximum totalrnBTEX concentration of 48,000 parts per billion (ppb). No non-aqueous phase liquid (NAPL) had beenrnobserved. Remedial action objectives for the site include restoring the groundwater to drinking water standardsrnfor each of these compounds. A removal action was initiated in November 2000 to address residualrncontaminants in an approximately 50 foot by 100 foot source area. Removal action goals were established tornreduce BTEX concentrations in the source area to approximately 300 ppb. Reduction of BTEX to this levelrnwould enable the remaining groundwater plume to naturally attenuate and meet the remedial action objectivesrnwithin a reasonable timeframe.rnIn-situ chemical oxidation proceeded with three phases of injection over a period of approximately one year.rnDuring the course of the three phases, a total of 12,200 gallons of 25% hydrogen peroxide was injected underrnpressure into 26 injection wells. Performance monitoring conducted after each phase showed a reduction inrncontaminant concentration (up to 98%) in the source area and a shrinkage of the size of the remaining source.rnHowever, after the third phase of treatment, contaminant levels in the vicinity of the former undergroundrnstorage tank rebounded to 28,500 ppb, significantly higher than treatment goals. The Navy is nowrnimplementing new remedies to complete the source area removal action.rnThe failure of chemical oxidation to reach treatment goals at this site is due to challenges in application of thisrntechnology at sites with complex hydrogeology. Steep hydraulic gradients and tight glacial till soils hinderedrnthe ability to get oxidant to low permeability zones that still retain source material. Geochemical data collectedrnduring the ISCO process also indicated that the peroxide and catalyst may persist in the subsurface forrnprolonged periods (> 150 days), thus complicating assessment of rebound and the actual effectiveness of therntechnology. Observations at this site suggest that it is unlikely to achieve the 90 to 95% reduction ofrncontaminant concentrations typically advertised for this technology in sites with difficult or complexrnhydrogeologic settings. Additional site characterization, process, and performance monitoring may bernnecessary to optimize injection delivery rates and the influence of injection points at similar sites.
机译：使用了Fenton试剂（过氧化氢和硫酸亚铁）进行了原位化学氧化（ISCO），并采取了去除作用，以解决马萨诸塞州Navalrn设施在封闭的地下石油储罐中的释放。这项技术未能达到治疗目标，对于将ISCO应用于复杂场所的挑战而言具有独特的意义。石油的释放发生在陡峭顶部的沙质冰川耕作单元中（水力传导率约为3.2×10-rn4cm / sec）。丘陵，污染物形成了一条狭窄的地下水羽，朝着湿地向下倾斜约700英尺。令人关注的污染物包括苯，甲苯，乙苯，二甲苯（BTEX），萘和2-甲基萘，BTEX的最大总浓度为48,000十亿分之一（ppb）。尚未观察到非水相液体（NAPL）。该场址的补救措施目标包括将上述每种化合物的地下水恢复至饮用水标准。 2000年11月开始采取清除行动，以处理大约50英尺乘100英尺源区域中的残留污染物。确定了清除行动目标，以将源区域中的BTEX浓度降低到大约300 ppb。将BTEX降低到此水平将使剩余的地下水羽流在合理的时间内自然衰减并达到补救作用的目标.rnn原位化学氧化在大约一年的时间内分三个阶段进行注入.rnn在三个阶段的过程中，在低压下将总计12,200加仑的25％过氧化氢注入26个注入井中。在每个阶段之后进行的性能监测表明，源区域的污染物浓度降低了（最高98％），剩余源的尺寸缩小了。然而，在第三阶段处理之后，前地下储藏室附近的污染物水平储罐反弹至28,500 ppb，明显高于治疗目标。海军目前正在实施新的补救措施，以完成源区清除行动。rn化学氧化未能达到该地点的处理目标是由于该技术在复杂水文地质地点的应用面临的挑战。陡峭的水力梯度和致密的冰川直到土壤阻碍了将氧化剂带入仍保留源物质的低渗透率区域的能力。在ISCO过程中收集的地球化学数据还表明，过氧化物和催化剂可能长时间（> 150天）持续存在于地下，从而使回弹评估和该技术的实际有效性变得复杂。在该站点的观察结果表明，在水文地质条件复杂或复杂的站点中，不太可能实现该技术通常宣传的90％至95％的污染物浓度降低。可能需要额外的站点表征，过程和性能监控，以优化进样速度和类似站点上的进样点的影响。

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