Development of an innovative approach for in situ treatment of PCB impacted sediments by microbial bioremediation

Project Summary Polychlorinated biphenyls (PCBs) are one of the most problematic of legacy contaminants. Persistent and mobile in the environment, PCBs are largely ubiquitous in depositional sediments of aquatic systems in industrial regions of the United States. Their relatively high toxicity and bioaccumulation potential cause elevated risk to both human and ecological receptors. As such, PCBs are often the primary risk driver at impacted sediment sites. Common practices for remediating PCB-impacted sediments are costly, often involving the physical removal of surficial sediments, capping the sediments or dredge depression with a multi-layered engineered cap, and disposal of the contaminated sediments in a confined landfill. An emerging strategy for effectively removing PCBs from sediments in-situ is the use of bioamended activated carbon (AC), which inoculates AC pellets with enriched cultures of PCB-degrading microbes. The co-investigators of this proposed research have performed the fundamental research behind the use of bioamended AC for remediation of PCBs from sediment and have developed and patented commercially-viable methods for growing, inoculating, and delivering the inoculated AC pellets to sediments. However, during the performance of pilot-scale studies using the bioamended AC, two factors that would limit the ready use of this technology for large, multi-acre sites were identified: 1) the large-scale growth, storage, and transport of anaerobic PCB degrading bacteria, and; 2) large-scale methods for inoculating AC pellets during application. The proposed research aims to address these limitations. The proposed research will test methods of culturing these organisms using time-release growth media, and develop and test storage vessels that maintain optimal environmental conditions for the long-term viability of the anaerobic organisms. These advances will ultimately allow for the delivery of large volumes of PCB degrading microorganisms for large-scale projects. The proposed research will also develop and test methods for the continuous, uniform inoculation of high volumes of AC pellets with the PCB-degrading microorganisms, which will allow for cost-effective application at multi-acre PCB-impacted sites. Coupled together, the proposed research is anticipated to result in a direct transfer of this technology from pilot-scale to full commercial viability. 1Narrative Polychlorinated biphenyls (PCBs) dominate the ecological and human health risk associated with contaminated sediments in the United States are a frequent cause of fish consumption advisories worldwide. Effective in situ treatments that can be rapidly deployed with minimal environmental disruption are critically needed to reduce the vast inventory of PCB contaminated sediments. We will test the scalability of a novel in situ bioremediation approach that employ microbes and activated carbon to treat PCB impacted sediments.