Formatted Title
An Examination of Field Data to Assess Activated Carbon Injection Effectiveness in Hydrocarbon Remediation
Background/Objectives
Activated carbon injection as a remedy for subsurface contamination has gained wide acceptance and is acknowledged for its effectiveness. Hundreds of closure letters, no further action letters, and similar documents have been issued by regulatory agencies both in the United States and abroad. This presentation will present evidence from initial emplacement, distribution, decreasing soil concentrations, changes in the microbial population, stable carbon isotopes, confocal microscope, and Scanning electron microscope, and regulatory closures to demonstrate the efficacy of BOS200® and BOS200+®. The data will be derived from multiple sites around the U.S., Canada, and Europe.
Approach/Activities
Field data from remediation sites using injection with BOS200 and BOS200+ were collected and examined for evidence of effectiveness and performance. The evidence collated includes soil cores examined visually and by brightfield microscope. To determine if post-injection contaminant concentrations in subsurface soils and aquifer materials changed, core contaminants were quantified by GC/MS and the results tested by Kruskal Waals analysis. Post-emplacement half lives were compared to published data. Stable carbon isotopes analysis was pursued for evidence of degradation. Soil gases were collated. Genome sequencing was used to characterize the microbial population. Confocal microscope was used to examine soil core microbial enrichment. Scanning electron microscope was used to examine microbial location on soils and the activated carbon.
Results/Lessons Learned
Data collected from remediation sites treated by BOS200® and BOS200+® injections were collected and examined for evidence of effectiveness and performance. Soil cores over a length of 10ft demonstrated an average of 53 activated carbon sightings per core. Brightfield microscope examination of the cores shows patterns distribution consistent with theoretical models and published data. Post-injection contaminant concentrations in soils demonstrated statistically significant decreases in contaminant concentrations. Calculated half lives post-emplacement are lower than published half lives for the same compounds. Stable carbon isotopes for benzene exceed δ13C ≥ 2o/oo. This is consistent with published values for nitrate, sulfate-reducing cultures, and methanogenic cultures (2 to 3.5 o/oo). Gases such as methane and butane rise post-injection. The microbial population is more abundant, richer, and even post-emplacement. Known hydrocarbon degraders show increased abundance. Quant Array® shows an increase in microbes having genes known to degrade hydrocarbons. The microbial population is enriched in the seams of activated carbon emplaced in the subsurface as shown by confocal microscope. Scanning electron microscope images indicated that microbes are enriched on the activated carbon in preference to native soils.