Biological Remediation of Petroleum Hydrocarbons in Soil: Suitability of Different Technologies Applied in Mesocosm and Microcosm Trials

Abstract

Here, we report the results of a study aiming at searching for a suitable biological technology for petroleum hydrocarbons (PHC) removal from a soil with weathered contamination. Different experiments were carried out, in parallel: a pilot project, in mesocosm-scale trials, which took place in the environment of a petroleum refinery, and within the same period, shorter experiments were also carried out outdoor, at microcosm scale, at lab environment. The following specific aims were persecuted: (1) comparison of the effectiveness of phytoremediation (different plants were tested, in parallel, for this purpose) with bioremediation (by means of indigenous microorganisms only—natural attenuation—and by using bioaugmentation) and (2) a possible synergistic effect resulting of simultaneous application of more than one remediation technology (phytoremediation, bioremediation and soil amendments). In all studies, the potential of each tested technology for remediation of recent and old contamination was also investigated, in parallel, since the degree of bioavailability of PHC can be very different in the two cases. The more relevant conclusion was that the salt marsh plant Scirpus maritimus could improve the efficiency of PHC degradation, relatively to natural attenuation. In the presence of this plant, degradation of PHC was not only faster but also extensive to weathered contamination, to which bioremediation was not effective, being particularly efficient for the heavier PHC from weathered contamination.