Bioremediation vs. Nanoremediation: Degradation of Polychlorinated Biphenyls (PCBS) Using Integrated Remediation Approaches

Integration of physicochemical and biological approach represented by sequential application of nanoscale zerovalent iron (nZVI dispersion) and bioaugmentation by bacterial strains isolated from the PCB-contaminated site seems to be an innovative way to remove the PCB contamination, which still persists in the environment. First, nanoremediation of the minimal mineral medium artificially contaminated with Delor 103 and of historically contaminated sediment was performed in 70% and 46% PCB removal efficiency. Integrated remediation was carried out as bionanoremediation initiated by addition of bacterial strains and finished by addition of nZVI dispersion Nanofer 25S. Nanobioremediation initiated by nZVI and followed by the addition of bacterial strains A. xylosoxidans, S. maltophilia, and O. anthropi was more effective and led to the increase of PCB degradation to 75%, 85%, and 99%. The bacterial mixed culture (BMC) consisted of 7 bacterial strains with PCB-degrading activity was used for integrated remediation, as well. By the nanobioremediation of the historically contaminated sediment, 78% degradation of PCBs was achieved by combining the nZVI and BMC, with the addition of non-ionic surfactant Triton X-100. The sediment was periodically reinoculated with fresh nZVI dispersion and BMC inoculum. The possible toxic effects of nZVI in concentration used in integrated remediation 2 g l−1 were evaluated on bacterial strains used for integrated remediation. The cell concentrations of the bacterial strains A. xylosoxidans, S. maltophilia, and O. anthropi, expressed as CFU ml−1, decreased in the presence of nZVI by 75%, 52%, and 61%, respectively.