Effective use of bimetals for above-ground treatment of contaminated groundwater

颗粒铁对地下水中氯代有机污染物的原位破坏效果显著。然而，通过在铁表面镀上极少量的第二种贵金属，如钯或镍作为催化剂，反应速率可以提高十倍或更多。不幸的是，由于在催化剂表面形成氧化铁薄膜，这种增加的反应性很快就丧失了。根据最近和初步的测试，我们假设在进水溶液中加入强酸或可能的螯合剂可以防止成膜，从而在相当长的一段时间内保持催化剂的高反应活性。将进行实验，以确定最有效的化学添加剂、最佳浓度、最有效的添加方法，并评估对进水流中其他无机成分的干扰可能性。这项技术有潜力成为一种极具成本效益的处理方法，用于抽水和处理地下水修复方案，或用于其他废物流。第二个项目涉及进一步发展和测试一种直接测量地下水流速的新装置（就地探头）。在之前的工作中，基于圆柱体周围流动的理论，开发了一种小直径的探头，可以直接测量地下水的流速。与其他设备相比，该探头具有特别的优势，因为它避免了井筛中使用的设备的不确定性和经验校准。它的独特之处在于，它可以用来测量地下水位以上的张力饱和区域内的速度。在拟议的研究中，将对该装置进行改进，使其可以用于更大的深度（目前的模型限制在地表以下约8米），并将对其进行改进，使其可以更准确、更方便地确定流向。新设备将在一系列水文地质环境中进行测试，特别感兴趣的是展示其在张力饱和区域内进行测量的实用性。

Granular iron has been shown to be highly effective for in situ destruction of chlorinated organic contaminants in groundwater. However, by plating a very small amount of a second more noble metal, such as palladium or nickel, onto the iron surface as a catalyst, reaction rates can be increased by a factor of ten or more. Unfortunately, this increase in reactivity is quickly lost as a consequence of iron oxyhydroxide films that form on the catalyst surfaces. Based on recent and preliminary tests, we hypothesize that the addition of a strong acid or possibly a chelating agent to the influent solution will prevent film formation and thus maintain the high reactivity of the catalyst over substantial periods of time.  Experiments will be conducted to determine the most effective chemical additive, optimum concentrations, most effective methods of addition and to evaluate the potential for interference with other inorganic constituents of the influent stream. This technology has the potential to be a highly cost-effective treatment method for pump-and-treat groundwater remediation schemes, or for other waste streams.    The second project concerns further development and testing of a new device (in situ probe) for direct measurement of groundwater velocity. In previous work, a small-diameter probe was developed, based on the theory of flow around a cylinder, that permitted direct measurement of groundwater velocity. The probe has a particular advantage over other devices in that it avoids the uncertainties and empirical calibrations of devices used in well screens. It is also unique in that it can be used to measure velocities within the zone of tension saturation above the water table. In the proposed study, the device will be modified such that it can be used to greater depths (current model limited to about 8 m below ground surface) and will be improved such that flow direction can be determined more accurately and much more conveniently. The new device will be tested in a range of hydrogeologic environments with particular interest in demonstrating its utility in making measurements within the zone of tension saturation.