Bioremediation of contaminated soils by hydrocarbons degrading bacteria and decontamination control

In this study three strains of Vibrio marine bioluminescent bacteria, have been employed to measure the biotoxicity of hydrocarbon contaminated soils from oil terminals. The evaluation of inhibitory effects of samples on emitted light was performed on soil before and during a four months bioremediation treatment by hydrocarbons degrading bacteria. The measurements were carried out at room temperature, using the microplate format, in medium containing 3% NaCl, and done both for short time of contact (60 minutes) and for longer time intervals (till 24 hours). The results were expressed as percentage of inhibition with respect to the blank emission. The yield of extraction of different solvents (acetone, dioxan, ethanol) was also evaluated by the bioluminescent test. After a short time of treatment (one month) the toxicity of the contaminated samples increased, since the bioremediation made available long chain hydrocarbons before in a not-soluble form. After longer period of bioremediation the toxicity decreased. The values of the of the percentage of inhibition obtained by the bioluminescent bacteria test (BLB) test were in good agreement with the hydrocarbons content, determined by gas chromatography. The BLB test could represent a useful biomonitoring tool to evaluate the changes occurring during remediation processes, even in case of on-field conditions. Moreover, the bioluminescence test allows to analyse at the same time, by using the microplate luminometer, a lot of samples in a relatively fast way, at low costs and using small volumes of reagents.