Theme: 02. Assessing Remediation Effectiveness

Topic Area: 02c. In Situ Activated Carbon-Based Amendments: Assessing Effectiveness and Performance

Formatted Title:

Colloidal Activated Carbon Applied into a Deep Aquifer to Expedite the Monitored Natural Attenuation of 1,2,3-TCP

Background/Objectives:

Background/Objectives. 1,2,3-TCP (TCP) is a recognized toxic contaminant known to government agencies, the private sector, and other stakeholders. It is a persistent groundwater pollutant and has been categorized as "likely to be carcinogenic to humans" by the EPA. While research papers have established mechanisms for the complete reduction of TCP to non-detectable levels, addressing contaminant levels in parts per billion concentrations can be challenging. Given the current focus on health-based screening levels as remedial objectives, using conventional remediation methods may result in extended site remediation timelines. It is speculated that using colloidal activated carbon (CAC) as a remediation amendment can expedite achieving remediation goals and support monitored natural attenuation.

Approach/Activities:

Approach/Activities. The presentation will cover data from a bench study, design verification, and a pilot application. The bench study revealed complete sorption of TCP using CAC, demonstrating its potential for immobilizing TCP at the project site. Further site-specific information was gathered during the design verification phase. A contaminant mass flux study, soil grain size analysis, and background groundwater chemistry provided the backbone for the pilot test design. The pilot test included dedicated injection wells to install the CAC in an aquifer over 100 feet below the ground surface. This configuration requires a small particle-sized activated carbon particle to achieve uniform product distribution into the transmissive zone. Information from a CAC field application and the results of performance monitoring will be presented.

Results/Lessons Learned:

Results/Lessons Learned. This study details the process from the initial bench study through pilot test application. The design verification work included a flux meter study where challenges in quantifying TCP mass flux were encountered. Nevertheless, it revealed important information about the grain size analysis and the uniformity of the target zone. This information guided the design of the deep injection well and product application. Performance data illustrates that the combination of CAC and monitored natural attenuation (MNA) offers a sustainable, long-term solution for TCP treatment. Based on estimated sorption rates, the treatment is projected to remain effective for over 30 years.

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Andrew Kiggen