Laboratory and field experiments on the microbiological restoration of polluted used oil refinery sites. Laboratory experiments and a review of literature. Final report

The aim of the study was to investigate the possibility of microbial degradation of organic pollutants in soil from an abandoned used oil refinery site. The following groups of key pollutants were involved: Aliphatic hydrocarbons, aromatic hydrocarbons, volatile chlorinated hydrocarbons, polyaromatic hydrocarbons, chlorinated phenols, polychlorinated biphenyls. The experiments were carried out in liquid and agar media, and in soil columns. Simple aliphatic and aromatic compounds were degraded fast, and they were preferably degraded if applied in a mixture with some chemically more complex compounds. The degradation degree decreased with increasing complexity of the experimental conditions. In soil samples about 30% to 60% of pollutants were removed in nine months. In the same period of time, the concentration of polychlorinated biphenyls was not reduced. In soil extracts a temporarily increase in toxicity was observed using bacteriological tests. In bulk soil samples the content of humic substances was enhanced due either to a coupling of pollutants with soil organic substances or to a novel formation of humic substances as a side effect of the biorestoration process. In general the laboratory experiments indicated some real possibilities but also limits for the biorestoration of the polluted refinery site. A comprehensive literature review was elaborated in this project; it is a part of this report. (orig.)