Grant: Collaborative Research and Development Grants

The use of nanoscale zero valent iron (nZVI) for remediation of contaminated sites has received significant attention in part due to the ability of nZVI to rapidly transform contaminants in controlled laboratory experiments. One problem that has hampered the widespread implementation of nZVI is poor subsurface mobility. Due to strong attractive forces, nZVI tends to agglomerate to micron size particles, limiting mobility in porous media. To overcome this problem nZVI particles may be stabilized by coating them with polymers making them stable in solution for days. Column experiments conducted in our laboratories, with polymer stabilized nZVI, indicate that this nZVI should be quite mobile in subsurface environments. Pilot studies that have applied nZVI at the field scale have reported limited mobility due to lack of or poorly formulated polymer stabilizers and inadequate nZVI injection rates. In this study nZVI field scale synthesis methods and injection methods will be developed and tested to overcome the problems that have plagued previous application of nZVI in field studies. This will involve determination of optimal polymer and nZVI concentrations and reactor design (for on-site synthesis of polymer-stabilized nZVI using the borohydride method) to minimize nZVI agglomeration and settling prior to and during nZVI injection. Field injection rates of nZVI will be determined from scale up of lab experiments conducted with field soils and numerical modelling. The field mobility of nZVI will be used to validate a numerical model. Once validated this model can be used to simulate nZVI remediation at other contaminated sites. This field study will conducted at Dow Chemical's Sarnia, ON facility with the strong support of CH2M Hill, Geosyntec and AMEC Geomatrix. Dow Chemical owns a number of locations in Canada where the subsurface has been impacted by chlorinated solvents. The development of innovative remediation alternatives is a key part of their environmental stewardship plan. CH2MHill, Geosyntec and AMEC Geomatrix are keenly aware of the contamination challenges that face many of their clients. The application of nZVI has the potential to meet many of these challenges.