ONGOING PILOT-SCALE FIELD STUDIES TO EVALUATE THE EFFICACY OF BIOREMEDIATION FOR TREATMENT OF PCB-IMPACTED SEDIMENTS

Treatment of PCB-impacted sediments with granular activated carbon (GAC) is gaining acceptance as an in situ method to sequester PCBs in sediments effectively minimizing their interaction with the biological food chain. The objective of this research is to develop and test the efficacy of a bioamended form of GAC embedded with microorganisms to sequester PCBs from the food chain and concurrently dechlorinate and degrade weathered PCBs in sediments. Two pilot studies were initiated to demonstrate and validate this environmentally sustainable technology in field sites contaminated with PCBs. Treatability studies in sediment mesocosms for both sites demonstrated PCB levels were reduced by up to 80 % after treatment by bioaugmentation. Effects of different quantities and types of inocula on total PCBs, congener distribution and bioavailability were determined to assess optimal field application. Among the challenges for the pilot field studies were development of methods for production level scale-up of the microorganisms without residual POPs, production of an activated carbon agglomerate, SediMite^TM, modified as a carrier for the bioamendments, development of a system to introduce active PCB transforming microorganisms into SediMite pellets during dispersal of the pellets at the site, and maintaining viability of the anaerobes and aerobes during the deployment process. Methodology, challenges associated with deployment at a sewage treatment pond and a wetlands tributary and preliminary results for the field demonstration studies will be discussed. The results of the pilot studies will access the feasibility of using bioremediation for full-scale treatment of PCB-impacted sites. In situ treatment by bioaugmentation where applicable would have a significantly reduced environmental impact compared with dredging by reducing the health risks associated with sediment disruption, reducing overall energy use, effectively negating the requirement for extensive waste management and substantial habitat restoration.