Removal of polychlorinated biphenyls (PCBs) from contaminated sediments is a priority because of their toxicity and ability to enter the food chain. Commonly remedies include dredging and capping that are associated with challenges such as disruption of habitats and high cost. While in situ microbial degradation of PCBs represents an improvement, previous attempts have failed because of PCB stability, low bioavailability, low abundance and activity of indigenous PCB-degrading microorganisms. Co-localizing PCB-degrading microbes on surfaces of sorptive particles as biofilms and utilization as a delivery system can provide a novel approach to address PCB contamination. In this study, biofilm covered adsorbent materials incl. AC were evaluated for enhancement of PCB dechlorination in sediment. Biofilms of anaerobic Dehalobium chlorocoercia and aerobic Burkholderia xenovorans strain LB400 were formed on sorptive materials. The materials consisted both of activated carbons and biochars based on plant and animal waste products such as coconut shell, pine wood, acai and bone. The formation of biofilm was quantified using culture methods and Q-PCR, Illumina sequencing and Confocal Laser Scanning Microscopy. The toxicity of 12 dioxin like congeners was investigated. Techniques in this study were: DNA extraction, q- PCR with specific 16S rDNA primers, identification by DHPLC and Illumina sequencing and microscopic analyses with DAPI, PNA-FISH and CLSM. Biofilm formation of DF1 and LB400 on sorptive materials was observed via microscopy and quantified via Q-PCR. Coal based activated carbon as well as bone based biochar showed the fastest colonization (1 day) and the highest number (10E9 cells per g) of bacteria after seven days (B. xenovorans). Anaerobic organohalide respiring biofilms inoculated into sediment mesocosms showed a 2-fold increase and enhanced PCB degradation (1.5 chlorines/biphenyl for biofilms (31%) vs. 0.3 chlorines/biphenyl for planktonic inoculum (6%) over 200 days. The bacterial diversity (up to eight species of organohalide respiring bacteria) was not affected. The application of biofilm-AC aggregates enhanced the PCB degradation in the mesocosms. This was due to PCB adsorption onto AC ensuring direct contact between the PCB degrading biofilms and adsorbed PCBs. This two-phased approach will provide an efficient and cost-effective method for delivering microorganisms for bioaugmentation of PCB contaminated sites.

Biofilms on activated carbon is a mediator for enhanced bioremediation of polychlorinated biphenyl (PCBs)

254th National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.