"Injection of Nano-Scale Iron for the In-Situ Remediation of Contaminated Groundwater"In order to remove contaminant plumes from the groundwater, permeable reactive barriers can be used. Instead of an excavated trench filled with granular zero-valent iron, a relatively new and promising method is the injection of nano-scale iron suspension in the subsurface using injection wells. The goal is to deposit the iron in the pores space and hence form an injected reactive barrier. However, little is known about the transport behavior of nano-scale iron during the injection. A better understanding of the transport behavior is necessary to design a field application such that the reactive barrier will be continuous in space and sufficiently wide. So far, there are no measuring techniques available to continuously and non-destructively determine the nano-scale iron concentration in the soil directly. Hence, the spreading and distribution of the nano-scale iron in the subsurface during injection could not be proven. In the presented work, measuring devices w ith a very high resolution based upon magnetic susceptibility have been developed to non-destructively determine the concentration of nano-scale iron during and after the injection in a column and in a large-scale container experiment. Several batch, horizontal column and container experiments were conducted to find the parameters controlling the reactivity, longevity and mobility of nano-scale iron in the subsurface.
In a field application the injection in a well would result in a radial flow field around the well. A large scale experiment was constructed to create such a 2-D radial flow field in a confined aquifer, also the experiment was equipped with the newly developed measuring technique. To predict the results of the large scale experiment and later a field application, a method is being developed to combine and upscale the results from column experiments.