Bioremediation of PCB-contaminated sediments and evaluation of their pre- and post-treatment ecotoxicity

The paper deals with the application of two perspective and promising bioremediation approaches, bioaugmentation and biostimulation, applied to sediment contaminated with polychlo-rinated biphenyls (PCBs) with the aim to enhance biodegradation of PCBs. Sediments were sampled from Strážsky canal, an industrial waste canal that flows from a former PCB-factory through the Laborec river into the Zemplínska šírava water reservoir, all located in the eastern part of Slovakia. Bioaugmentation of sediments was performed in microcosms using two bacterial isolates with PCB-degradation ability obtained from the contaminated sediment: Achromobacter xylosoxidans, Stenotrophomonas maltophilia. Biostimulation was performed using an addition of cut plants containing terpenes, known as PCB-inducers (ivy leaves and pine needles). Ecotoxicity of the contaminated sediments was evaluated pre- and post-treatment using biotests of the standard aquatic plant Lemna minor, standard contact test using Lactuca sativa var. capitata, and the bioluminescent bacteria Vibrio fischeri. Biostimulation treatment using ivy leaves revealed higher degradation of detected PCB congeners than that achieved by the addition of pine needles, but moderately higher post-treatment toxicity of the sediment to the bioindicator Lemna minor.