Sediments impacted with chemicals of concern are an issue throughout the country, and existing remediation options are often slow and expensive. This project assisted in the development of a novel approach to addressing aquatic sediments impacted with polychlorinated biphenyls (PCBs) and also developed management tools that will be applied in situ, resulting in more efficient and cost-effective reduction of risk at these sites.

The objective of this project was to apply a biofilm-based delivery system to wea­the­­red aquatic sediments impacted with low PCB concentrations in order to promote enhanced dechlorination activity and subsequently complete PCB mineralization. The overall hypothesis of this work was that the rate and extent of PCB dechlorination in aquatic sediments can be enhanced by the presence of active mi­cro­bial biofilms associated with sorptive surfaces, while the PCBs simultaneously would be sequestered at the sorptive surface and unavailable for benthic organisms. The activity of the biofilm-based system will benefit from active PCB-dechlorinating bacteria grown to a high density, while located at the surface of the sequestering activated carbon or other sorptive surfaces.

This work was conducted in two phases with proof-of-concept work conducted during Phase I followed by testing the application of dechlorinating bacterial biofilms on sorptive materials for treating sediments with lower total levels of weathered PCB typically found in the environment during Phase II. The goal for this research project was to obtain full degradation of PCB in weathered sediment by focusing on the first and rate-limiting step of the initial anaerobic dechlorination and subsequently enable aerobic degradation by applying biofilm inoculum associated with activated carbon as a delivery system.

Technical Approach

In Phase I, the proof-of-concept for the biofilm-based delivery system was conducted using laboratory mesocosms containing high concentrations of Aroclor 1248 that were inoculated with biofilm-covered activated carbon particles. Biofilms of anaerobic Dehalobium chlorocoercia DF1 and anaerobic enrichments from wastewater were formed on the sorptive surfaces and the mature biofilms were inoculated into PCB-impacted sediment mesocosms, where total PCB and individual congener concentrations were determined. Molecular techniques including DNA extraction, quantitative PCR with specific 16S rDNA primers for dechlorinating bacteria, identification by DHPLC, and sequencing were applied. Also, several microscopic analyses were developed to qualitatively and quantitatively analyze the PCB dechlorinating biofilms such as the fluorescent stain DAPI (4',6-diamidino-2-phenylindole), Peptide Nucleic Acid-Fluorescence In Situ Hybridization (PNA-FISH), Scanning Electron Microscopy (SEM), and Confocal Laser Scanning Microscopy (CLSM).

During Phase II, bioaugmentation performed with PCB-degrading biofilm inoculum was applied for both anaerobic and aerobic biodegradation processes. It was expected that application of biofilm inoculum would increase reductive dechlorination of impacted sediment containing low concentrations of weathered PCB compared to bioaugmentation using liquid inoculum. Furthermore, mineralization and removal based on combined aerobic/anaerobic biofilm inoculum was expected. The experiments were performed in mesocosms containing impacted sediment.


Phase I Results

Biofilm formation of Dehalobium chlorocoercia DF1 and anaerobic enrichments from wastewater was observed via multiple fluorescence staining and microscopic techniques. When the biofilms were inoculated into sediment mesocosms with high concentrations of Aroclor 1248, the bacterial numbers increased 2-fold and PCB dechlorination was enhanced by 31% for biofilms (1.5 chlorines/biphenyl) vs. 6% (0.3 chlorines/biphenyl for planktonic inoculum) over 200 days. The compositions of the bacterial populations were not influenced, thus not causing the difference in dechlorination. The enhanced PCB dechlorination might have been due to PCB adsorption onto the activated carbon particles ensuring direct contact between the PCB dechlorinating biofilms and the adsorbed PCBs. In summary, the proof-of-concept biofilm based two-phased delivery system can provide an efficient and cost-effective method for delivering microorganisms for bioaugmentation of PCB contaminated sites, thus enabling complete onsite bioremediation. The results of this study can be found in the Phase I Final Report. 

During Phase II, seven separate studies were conducted to address the project objectives: 

  • Study 2 showed that aerobic and anaerobic biofilms could successfully be grown on granular activated charcoal surfaces. (Study 1 described the project timeline.) 
  • Study 3 showed that biofilms made up by Paraburkholderia xenovorans strain LB400 developed on each of the tested sorptive materials. 
  • Study 4 showed that the anaerobic dechlorinating bacterium DF1 could be scaled up, grown, and maintained using tandem 20 L bioreactors to numbers that were applicable and effective for full scale implementation. 
  • Study 5 showed that the rate of the single congener PCB 61 (2,3,4,5-CB) was found to be linearly dependent on the freely dissolved concentration in both sediment and in sediment-free microcosms. 
  • Study 6 showed that dehalorespiring biofilms formed on all carrier materials tested with a preference for sorptive carbonaceous materials, which subsequently was shown to be the most important mechanism for formation of biofilm. 
  • Study 7 showed that dechlorination of weathered PCB in Grasse River sediment occurred in the presence of biochar, liquid bacterial inoculum, and biofilm formed on biochar. 
  • Study 8 showed that enhanced kinetic effects on organohalide respiration were not observed in the presence of black carbon materials when the black carbon was first equilibrated with sediments followed by the addition of DF1.


This project aimed to develop a novel approach to addressing PCB-impacted sediments and management tools by performing laboratory-based studies that subsequently can be transferred and expanded for application in situ. The goal was to more efficiently and cost-effectively reduce the risk from PCBs in sediments.

The results from this project have expanded the knowledge about mechanisms and rates for bioremediation of weathered PCB-impacted sediment. In addition, the project team has developed several new analytical approaches that will be applicable for treatment of other environmental compartments that are impacted with PCB and other persistent organic pollutants. These approaches included a predictive tool for PCB microbial dechlorination kinetics, quantitative methods for determining biofilm formation, and presence on materials as well as scale up of microbial inoculum. (Project Completion - 2024)


Capozzi, S.L., C. Bodenreider, A. Prieto, R.B. Payne, K.R. Sowers, and B.V. Kjellerup. 2018. Colonization and Growth of Dehalorespiring Biofilms on Carbonaceous Sorptive Amendments. Biofouling, 35:50-58. doi.org/10.1080/08927014.2018.1563892.

Capozzi, S.L., R. Jing, L.A. Rodenburg, and B.V. Kjellerup. 2019. Positive Matrix Factorization Analysis Shows Dechlorination of Polychlorinated Biphenyls During Domestic Wastewater Collection and Treatment. Chemosphere, 216: 289-296. doi.org/10.1016/j.chemosphere.2018.10.151.

Demirtepe H., B. Kjellerup, K.R. Sowers, and I. Imamoglu. 2015. Evaluation of PCB Dechlorination Pathways in Anaerobic Sediment Microcosms using an Anaerobic Dechlorination Model. Journal of Hazardous Materials, 296:120-127. doi.org/10.1016/j.jhazmat.2015.04.033.

Horwat M., M. Tice, and B. Kjellerup. 2015. Biofilms at Work: Bio-, Phyto- and Rhizoremediation Approaches for Soils Contaminated with Polychlorinated Biphenyls. AIMS Bioengineering, 4:324-334. doi.org/10.3934/bioeng.2015.4.324.

Jing, Ran and B.V., Kjellerup. 2020. Predicting the Potential for Organohalide Respiration in Wastewater? Comparison of Fecal and Wastewater Microbiomes. Science of the Total Environment, 705:135833. doi.org/10.1016/j.scitotenv.2019.135833.

Jing, R., S.L. Capozzi, S. Fusi, C. Alisha, and B.V. Kjellerup. 2018. Distribution of Polychlorinated Biphenyls in Effluent from a Large Municipal Wastewater Treatment Plant: Potential for Bioremediation? Journal of Environmental Sciences, 75:42-52. doi.org/10.1016/j.jes.2018.06.007.

Jing, R., S. Fusi, and B.V. Kjellerup. 2018. Remediation of Polychlorinated Biphenyls in Contaminated Soils and Sediments: State of Knowledge and Perspectives. Frontiers in Environmental Science, 6:79. doi.org/10.3389/fenvs.2018.00079.

Kaya, D., K.R. Sowers, H. Demirtepe, B. Stiell, J.E. Baker, I. Imamoglu, and B.V. Kjellerup. 2019. Assessment of PCB Contamination, the Potential for In Situ Microbial Dechlorination and Natural Attenuation in an Urban Watershed at the East Coast of the United States. Science of the Total Environment, 683: 154-165. doi.org/10.1016/j.scitotenv.2019.05.193.

Kjellerup B., C. Naff, S.J. Edwards, U. Ghosh, J.E. Baker, and K.R. Sowers. 2014. Effects of Activated Carbon on Reductive Dechlorination of PCBs by Organohalide Respiring Bacteria Indigenous to Sediments. Water Resources, 52:1-10. doi.org/10.1016/j.watres.2013.12.030.

Lombard N.J., U. Ghosh, B. Kjellerup, and K.R. Sowers. 2014. Kinetics and Threshold Level of 2,3,4,5-tetrachlorobiphenyl Dechlorination by an Organohalide Respiring Bacterium. Environmental Science & Technology, 48(8):4353-60. doi.org/10.1021/es404265d.

Ming-ch'eng Adams C.I., J.E. Baker, and B. Kjellerup. 2016. Toxicological Effects of Polychlorinated Biphenyls (PCBs) on Freshwater Turtles in the United States. Chemosphere, 154:148-154. doi.org/10.1016/j.chemosphere.2016.03.102.

Needham T.P., R.B. Payne, K.R. Sowers, and U. Ghosh. 2019. Kinetics of PCB Microbial Dechlorination Explained by Freely Dissolved Concentration in Sediment Microcosms. Environmental Science & Technology, 53(13):7432-7441. doi: 10.1021/acs.est.9b01088.