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 pollutants. 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 Superfund sediment sites. Common practices for remediating PCB-impacted sediments are costly, often involving the physical removal of contaminated sediments and disposal of the sediments in a confined landfill, and/or installation of a multi-layered engineered cap over the contaminated sediments. An emerging strategy for effectively removing PCBs from sediments in situ is the use of bio-amended activated carbon (AC), which employs AC pellets inoculated with enriched cultures of PCB-degrading microbes. The co- investigators of this proposed research have performed the fundamental research behind the use of bio- amended AC for remediation of PCBs in sediment and have patented commercially-viable methods for growing, inoculating, and delivering the bioamended AC pellets to sediments. The prior Phase I project, a collaboration between university scientists and RemBac Environmental, addressed two factors that limit the ready use of this technology for large, multi-acre sites: 1) the large-scale growth, storage, and transport of anaerobic PCB degrading bacteria, and; 2) large-scale methods for inoculating and deploying the bioamended AC pellets. The PCB halorespiring anaerobe was successfully scaled up to the maximum density in a bench-scale bioreactor, methods were developed for storage of cells by lyophilization and two approaches were successfully tested for the continuous, uniform inoculation of high volumes of AC pellets with the PCB-degrading microorganisms. The proposed research will advance the technology towards commercialization by demonstrating the efficacy of the methods developed in Phase I for scaled up production at a commercial facility, and perform a pilot-scale demonstration of the technology at the New Bedford Harbor Superfund Site (NBHSS). PCB degrading microorganisms will be scaled up to cell numbers sufficient to treat over 1 acre, and AC pellets will be inoculated on-site using methods developed in Phase I to assess the efficacy of the application methods in a tidal marsh. PCB levels in sediment and water will be assayed after one year to 1) assess the effectiveness and environmental impact of the treatment, and 2) assess the stability of the treatment with tidal activity. Finally, a cost analysis conducted for the entire process to assess the commercial viability of bio-amended AC as a cost- effective treatment for PCB impacted sites. The proposed research is anticipated to result in a direct transfer of this technology from pilot-scale to full commercial viability through an active collaboration with the U.S. Environmental Protection Agency (USEPA), U.S. Army Corps of Engineers (USACE), engineering consultants, and Superfund site stakeholders.