Vegetal layer restoration of contaminated sites from petroleum industry using sewage sludge

Soil is a non-renewable natural resource, extremely valuable for maintaining life on Earth. Large areas of soil are often polluted with petroleum products as a result of various human activities. In this case, it is necessary to remediate the contaminated soils from the oil industry and return them to the natural and economic circuit. In addition, large quantities of sewage sludge are generated daily by sewage treatment plants. The purpose of this study was to use the soil subjected to a bioremediation experiment with sewage sludge as support for the development of a new vegetal layer to restore the natural balance. The grass was sown in the land, which had previously been treated with sewage to monitor its development. Through microbiological analysis, we observed that soil and sewage sludge mixtures have a high content of heterotrophic bacteria and filamentous fungi that could play an important role in seed germination. IR (infrared spectroscopy) analysis revealed a decrease in hydrocarbon concentrations in the petroleum- contaminated soil treated with sewage sludge. By using the combined methods SEM-EDX (scanning electron microscopy – energy dispersive X-ray), we also analyzed the soil microstructure and the distribution of chemical elements to highlight the plants' evolution. The present study considers soil regeneration in areas contaminated with petroleum products and opens new perspectives for the use of sewage sludge in the ecological reconstruction of petroleum-contaminated sites.