1,2,3-trichloropropane (TCP) was used historically as a paint and varnish remover, a cleaning and degreasing agent, a manufacturing solvent, and was a common component of soil fumigants previously used widely in agriculture.
TCP is characteristically mobile in the subsurface and resistant to natural attenuation, and its persistence has resulted in wide-spread impacts to water supply systems. The U.S. Environmental Protection Agency (EPA) is evaluating TCP as part of the Third Unregulated Contaminant Monitoring Rule (UCMR3), which is used to determine whether a contaminant will be subject to future regulation, while individual states have or are in the process of developing regulatory levels for TCP that are as low as 0.0005 micrograms per liter.
TCP is mobile in the subsurface and resistant to natural attenuation. Compared to more halogenated compounds, TCP is less likely to sorb to solid material or partition into the vapour phase. Remediation options for TCP are limited, particularly at current and anticipated future regulatory levels. Treating groundwater with low concentrations of TCP presents unique remedial challenges. Remedial technologies that have been evaluated or implemented at scales ranging from laboratory treatability studies to full-scale field implementation include in-situ bioremediation (ISBR), in-situ chemical reduction (ISCR), and in-situ chemical oxidation (ISCO).
One innovative treatment process that produces promising rates of TCP degradation is ISCR with zero-valent zinc (ZVZ). This presentation will summarize results from laboratory tests, small-scale pilot and field scale pilot studies and performance monitoring designed to collect data to demonstrate and validate the use of ZVZ to promote abiotic ISCR of TCP in groundwater. In addition, data is being collected to develop performance metrics evaluating ZVZ delivery and treatment efficacy, engineering design, regulatory approval and cost benefit analysis. This work is being conducted in conjunction with academic partners at the Oregon Health & Science University with funding from the US Navy Environmental Sustainability Development to Integration Program (NESDI) and an Environmental Security Technology Certification Program (ESTCP) grant.
Current approaches for remediating TCP in groundwater are infeasible or cost prohibitive. Since TCP has been identified as an emerging contaminant by the federal government, successful development and transition of ZVZ technology can help lead to expedited facility clean-up and closure. In addition, ZVZ technology may be more broadly applicable to the wider family of lesser chlorinated hydrocarbons, a particularly recalcitrant class of compounds that is challenging to remediate.