Remediation of organic-contaminated groundwater with granular iron: Small-scale field tests

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Industrial solvents such as trichloroethene (TCE) tetrachlorethene (PCE) and other chlorinated organic chemicals were recognized as significant groundwater contaminants in the early 1970s.  The use of granular iron, configured as an in situ permeable "wall", for degrading these compounds was pioneered at the University of Waterloo, and for the past several years, research on the topic has been supported by an NSERC Industrial Research Chair (IRC).  This proposal includes six sub-projects primarily directed at evaluating the field applicability of several of the promising results obtained from earlier laboratory tests.  A novel in situ flow-through column device will be developed that should provide an accurate representation of the performance of an in situ granular iron permeable reactive barriers (PRB).  This device will be used to examine, under natural-field conditions, the potential for degradation of two classes of compounds, chlorinated butenes and butadienes and nitro toluenes.  Kinetics of degradation, degradation products, competitive effects, and the effect of in situ temperature, and inorganic chemical composition of the groundwater will be examined.  In a further study, a mathematical model previously developed for predicting the long-term performance will be tested against the actual performance of a PRB that has been operating for a period in excess of five years.  An additional study concerns the testing and performance of a prototype reactor for above-ground treatment.  Laboratory tests have shown the addition of a small amount of acid to be highly effective in preventing the passivation of metal catalysts contained in flow through reactors.  This will be further evaluated in a prototype reactor installed at a commercial site in Waterloo.   The results should provide important and practical information concerning the field behaviour of various contaminants, potentially broadening the applicability of the technology.  The in situ column device is novel, with market potential, and the reactor, if successful could provide an important and highly marketable technology for above ground treatment of contaminated water.