Colonization and growth of dehalorespiring biofilms on carbonaceous sorptive amendments

Abstract

Removal of polychlorinated biphenyls (PCBs) from contaminated sediments is a priority due to accumulation in the food chain. Recent success with reduction of PCB bioavailability due to adsorption onto activated carbon led to the recognition of in situ treatment as a remediation approach. In this study, reduced bioavailability and subsequent break-down of PCBs in dehalorespiring biofilms was investigated using Dehalobium chlorocoercia DF1. DF1 formed a patchy biofilm ranging in thickness from 3.9 to 6.7 µm (average 4.6 ± 0.87 µm), while the biofilm coverage varied from 5.5% (sand) to 20.2% (activated carbon), indicating a preference for sorptive materials. Quantification of DF1 biofilm bacteria showed 1.2–15.3 × 10⁹ bacteria per gram of material. After 22 days, coal activated carbon, bone biochar, polyoxymethylene, and sand microcosms had dechlorinated 73%, 93%, 100%, and 83%, respectively. These results show that a biofilm-based inoculum for bioaugmentation of PCBs in sediment can be an efficient approach.

Keywords:

• Dehalorespiring biofilms
• activated carbon
• polychlorinated biphenyls (PCBs)
• quantitative confocal laser scanning microscopy (Q-CLSM)
• contaminated sediment

Acknowledgements

The authors are grateful to Betsey Pitts and Heidi Smith (Center for Biofilm Engineering, Montana State University), Laura Kellerman and Manjula Nandasiri (Imaging and Chemical Analysis Laboratory, Montana State University) during biofilm imaging and analysis.

Disclosure statement

The authors declare no competing financial interest.

Additional information

Funding

This work was funded by Strategic Environmental Research and Development Program (SERDP) [project ER-2135].