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Denis O'Carroll
Denis O'Carroll

Associate Professor
University of New South Wales - Australia

Dr. O’Carroll is a Professor in Civil and Environmental Engineering and Managing Director of the Water Research Laboratory at UNSW Australia. He is an Associate Editor for Water Resources Research and the Journal of Contaminant Hydrology. He has completed a number of field trials investigating the utility of nZVI and sulfidized nZVI formulations developed in his laboratory for contaminated site remediation. This includes the impact of nZVI on long term in-situ bioremediation at these field trials. He also has ongoing field trials assessing the utility of electrokinetics to emplace amendments in clay as well as research projects improving the understanding of PFAS environmental fate as well as the development of PFAS remediation technologies.


Field performance of Sulfidized Nanocale Zero Valent Iron (S-nZVI) and comparison to traditional nZVI

Sulfidation of nZVI has been proposed as a means of overcoming many of the barriers that have limited broad nZVI application. The treatment of nZVI with lower valent forms of sulfur compounds (i.e., sulfidation or S-nZVI) inhibits its reaction with water, leading to improvements in the longevity and selectivity of the particles. This presentation will discuss and compare field scale injection experiences from multiple field trials where we injected either nZVI or S-nZVI stabilized with carboxyl methyl cellulose (CMC) to remediate chlorinated hydrocarbon impacted sites. Both nZVI and S-nZVI stabilized with CMC are quite mobile in permeable aquifer materials facilitating their emplacement in the contaminated source zone for contaminant degradation. nZVI and S-nZVI led to significant decreases in contaminant mass as well as significant changes in contaminant distribution. At the S-nZVI field trial changes in cVOCs concentrations and compound specific isotope analysis (CSIA)data suggest both sequential hydrogenolysis as well as reductive β-elimination as the possible transformation mechanisms during the short-term abiotic and long-term biotic dechlorination. One of the most positive outcomes of the CMC-S-nZVI field trial is the non-accumulation of lower chlorinated VOCs, particularly vinyl chloride, in comparison to previous nZVI field trials. Post-treatment soil cores also revealed significant decreases in cVOCs concentrations throughout the targeted treatment zones. Results from these studies suggest that S-nZVI has the potential to overcome many of the initial challenges limiting nZVI application.

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