Biological treatment of PAH contaminated soil extracts

The biological treatment of a soil extract sample from a former Manufacturing Gas Plant was tested in several two-phase liquid systems. Silicone oil, dodecane, tetradecane and hexane were first tested as organic phase for the removal of phenanthrene, acenaphthene and pyrene by a well-adapted phenanthrene degrading community. The contaminants were removed in the same order of magnitude in all the biphasic systems showing that the four solvents were suitable. The same microflora was then tested for the treatment of a real soil extract sample in silicone oil. Phenanthrene was totally removed after 20 days of incubation showing no inhibition effect of other extract components on the microbial community. A new microbial consortium, isolated from the same contaminated soil, was then tested with the four organic solvents for the treatment of soil extract. Only silicone oil allowed PAH removal and strong evidence was found that organic compounds other than the PAHs were present in the extract and competed with the pollutants as carbon source. This should be taken into consideration in future studies aiming at combining soil extraction with biological treatment.