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

粒状铁已被证明是非常有效的原位破坏地下水中的氯化有机污染物。然而，通过在铁表面上镀上非常少量的第二种更贵的金属，如钯或镍作为催化剂，反应速率可以提高十倍或更多倍。不幸的是，由于在催化剂表面上形成羟基氧化铁膜，这种反应性的增加很快丧失。基于最近的和初步的测试，我们假设向流入溶液中加入强酸或可能的螯合剂将防止膜形成，从而在相当长的时间内保持催化剂的高反应性。 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，并评估对流入物流中其他无机成分的干扰潜力。这项技术有可能成为一种高成本效益的处理方法，用于泵和处理地下水修复计划或其他废物流。 第二个项目涉及进一步开发和测试一种直接测量地下水流速的新装置（现场探头）。在以前的工作中，开发了一个小直径的探头，基于绕流理论的圆柱体，允许直接测量地下水流速。该探头具有优于其他设备的特别优势，因为它避免了井筛中使用的设备的不确定性和经验校准。它的独特之处还在于它可以用来测量地下水位以上张力饱和区内的速度。在拟议的研究中，将对该装置进行修改，使其能够用于更大的深度（目前的模型限于地面以下约8米），并将进行改进，使其能够更准确和更方便地确定流动方向。新设备将在一系列水文地质环境中进行测试，特别关注其在张力饱和区进行测量的实用性。

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.