Abstract:Permeable reactive barriers have been extensively used and investigated. Their disadvantages include the cost of implementation which increases with increasing depth, the requirement of open access to machinery and the restriction to the treatment of contaminant plumes. A relatively new and promising method to overcome these obstacles is the injection of nano-scale zero-valent iron suspended in water into the subsurface. The idea is that this iron will be transported with the injected water to form a reactive wall (plume treatment). Alternatively, the iron may be injected directly into the source (source treatment).
The method has been applied at several locations around the world; however, to date not much is known about the transport distance of nano-iron and hence the effectiveness, of this technology. While reports on transport distance range from few centimetres to several meters (or even tens of meters), no direct measurement of the iron distribution has been made and reports about the distance are based on the measurement of secondary parameters.
During previous experiments at VEGAS (Feasability Study on the In-Situ Application of Reactive Nano-Sized Iron Particles to Remediate CHC-Contaminations), horizontal column experiments were performed. Additionally, a measuring technique, based upon the magnetic susceptibility was developed to determine the transport distance of the nano-iron.. In these experiments, the qualitative and (semi-)quantitative influence of various parameters on the transport distance were investigated.
In the current project the column experiments will be continued in order to better quantify the parameters that influence the transport distance of nano-iron.
In addition, batch and column experiments will be done to test the long-term chemical performance of nano-iron.
The transport experiments will be extended to a three dimensional radial flow field induced by an injection well at a near-field scale. The measuring technique will be adapted for three dimensional detection of the nano-iron spreading. A field trail will follow when the indoor experiments are completed.