Decrease of extractable PCBs level in soilmicrocosms: influence of granular activated carbon and inoculation by natural microbial consortia
Abstract
A bacterial consortium selected from a PCB-contaminated soil was used to obtain inocula for aerobic PCBs degradation experiments. These inocula were prepared either as planktonic culture, or with granular activated carbon (GAC) used as support for biofilm development. The inocula were mainly composed of members of the α-, β- and γ- subclasses of the Proteobacteria phylum. The most represented bacteria, affiliated to the genera Pseudomonas, Achromobacter, Ochrobactrum and Halomonas, are commonly associated with soils enriched with biphenyl or PCBs. The decrease of extractable PCB congeners levels was explored in the PCBs polluted soil from which the inocula were selected, spiked or not with Aroclor 1242. When Aroclor 1242 was added to soil, mainly low-chlorinated congeners were removed, whereas in native polluted soil, decrease of extractable concentrations was observed for a larger spectrum of congeners. Inocula containing biofilm-coated GACs were less efficient than planktonic-cell culture, to decrease total amounts of extractable PCBs . This limitation was possibly due to the differences in the bacterial composition of the inocula prepared with and without GAC. Moreover, some PCBs adsorbed onto the GAC might be non-bioavailable. The inoculation with biofilm-coated GAC accelerated aerobic removal of the extractable PCBs during the three first months of incubation, albeit limited in terms of total PCBs removal.