Source zone remediation by zero valent iron technologies

Chlorinated solvents have been widely used as industrial solvents. Decades of extensive use have resulted in the contamination of an estimated 800,000 sites in the western world alone. A medium to high risk of problems related to dense non-aqueous phase liquids (DNAPLs) has been assessed to exist at a fifth of these contaminated sites. These source zones pose a serious threat to soil and groundwater quality. Remediation of the heterogeneous source zones is challenging due to irregular downwards migration patterns in the subsurface, low aqueous solubility and matrix diffusion. To protect the soil and groundwater resources from long-term deterioration, the development of in situ technologies suitable for remediation of DNAPL is warranted. Currently, an array of aggressive in situ remediation technologies remediation exists. These technologies may be suitable under various site specific conditions; however, most of them are limited by subsurface heterogeneities and/or the risk of inadvertent DNAPL displacement during field application. This thesis presents the results of an investigation of the potential for remediation of chlorinated solvent source zones by emerging zero valent iron (ZVI) based technologies. These in situ remediation technologies include the injection of nanoscale ZVI (nZVI) particles and the addition of ZVI and clay through soil mixing (ZVI-Clay soil mixing). The investigation of the nZVI technology is based on an elaborate literature review, while the investigation of the ZVI-Clay soil mixing technology is based on experimental data from bench-scale studies and field applications. Generally, both technologies are efficient at degrading chlorinated solvents with only a minor production of persistent chlorinated intermediates. To date, the nZVI technology has been applied at around 40 contaminated sites, while the ZVI-Clay soil mixing technology has been applied in full-scale at 9 contaminated sites. Scarce performance data exist for most of these sites; this limits the assessment of the potential for source mass depletion and risk mitigation at down-gradient receptors by the ZVI technologies. When investigating the nZVI technology specifically, this technology utilizes the decreased particle size (