Nano-scale Zero Valent Iron Research

3. Field Work

Field tests have been conducted in two locations, London and Sarnia. Brief descriptions about each site are below.

London Field Trial

NZVI injection at contaminated site in London, ON.

Nano-scale Zero Valen Iron (nZVI) slurry was injected into the subsurface at a contaminated site in London, ON. This site was a former military vehicle assembly facility which was used as maintenance depot after the Second World War. Currently the site is owned by the Department of National Defense (DND). The shallow aquifer at the site is reported to be contaminated with chlorinated volatile organic compounds (cVOCs), with trichloroethylene (TCE) being the primary contaminant of concern. The objectives of the study were to observe the nZVI mobility through the contaminated subsurface and to evaluate the degradation of contaminant resulting from nZVI delivery to it. Freshly onsite synthesized stabilized nZVI was gravity fed through a monitoring well and samples were collected periodically from the injection well as well as from two other monitoring wells. Long term monitoring of groundwater samples has shown that more than 99% of initial TCE was degraded in 16 months. It is hypothesized that abiotic nZVI reaction coupled with enhanced long term bio-degradation has resulted in TCE degradation at the site. This study suggests that injection of nZVI can be a viable tool for subsurface remediation.

Sarnia Field Trial

NZVI injection at contaminated site in London, ON.

Sarnia, Ontario is the site of an ongoing study evaluating the field scale application of nZVI. Seven hundred litres of nZVI particle slurry was injected into an abandoned subsurface corridor containing underground utilities. The study area was subject to contamination by chlorinated solvents and is part of a remediation effort targeted at recalcitrant compounds and “hot spots” of contamination. Previous field studies injecting nZVI have experienced challenges with aggregation of the highly reactive nZVI particles hindering subsurface delivery via conventional direct push wells. nZVI in this study was shown to travel well within the subsurface due to a biodegradable polymeric coating that was added during synthesis. Significant nZVI particle characterization was carried out in the project in order to evaluate particle mobility using methods previously not studied at the field scale. It was found that the addition of polymer addresses the delivery problems, but also acts as a substrate for subsequent bioremediation that occurs following injection. Chlorinated compound concentrations were monitored in detail within the study area following nZVI injection area. Degradation was observed immediately following nZVI injection and further degradation was monitored over several years due to the effect of microorganisms that were stimulated on site due to injection. The field study is a collaborative project between a multidisciplinary team of students, researchers, and engineers from Western University, the University of Toronto, and industrial partners at CH2M Hill Canada Ltd.