Formatted Title
Colloidal Activated Carbon Injections for Hydrocarbon Plumes: Trends and Lessons Learned from a Review of 28 Sites
Background/Objectives
Background/Objectives. Colloidal activated carbon (CAC) is a proven remediation amendment with a strong affinity for many toxic soil and groundwater contaminants. When combined with a destructive mechanism, it is possible to rapidly adsorb contaminants onto the carbon particles, with degradation accomplished through biological or abiotic processes. Over 870 applications of CAC have been applied worldwide, with both field and lab studies supporting the technology’s performance.
This talk intends to present information on types of CAC sites and provide information on common site types, contaminant concentration ranges treated, geology, and expected performance and critical best practices to achieve desired site goals.
Approach/Activities
Approach/Activities. Proprietary online design software data were aggregated to typical design variables such as treatment area, soil type, and contaminant concentrations from over 1,750 unique designs. This data set offers a fascinating snapshot of a typical CAC site. Furthermore, the percent fraction of BTEX versus TPH-G or TPH-D for the sites was evaluated and plotted.
Monitoring well data from +30 sites were tabulated and reduced to data sets with at least three post-application monitoring points to also help plot trends and outline best practices for application. This data helped visualize performance trends for benzene, MTBE, and BTEX as well as typical application type and soil type. The presentation will also introduce functional gene data from a smaller data set to offer insight on microbial response trends (QuantArray® -Petro) post-application.
Results/Lessons Learned
Results/Lessons Learned. UST sites tend to have data gaps primarily due to tighter budgets and less perceived need to collect a broad range of chemical and geochemical parameters. Benzene reductions from the data ranged from 98.3 to 99.6% reductions at a subset of 46 wells from 17 sites for two years post-application. Sites with MTBE impacts performed exceptionally well and often achieved a +99.6% reduction which has been sustained for two years post-injection.
The sites that deviated from recommended spacing, injection dilution, and dosing guidelines tended to perform worse. Spacing of the CAC amendment points between 5 to 6.5 feet on-center for high silt/clay sites or mostly sand sites (respectively) performed best in evaluating the aggregate data. The use of CAC as a visible field tracer to make real-time adjustments on distribution also significantly impacted performance.