Assessment of a Bioremediation Process for Hydrocarbons Polluted Soil

Abstract Throughout the world, the oil industry generates polluted soils contaminated with crude oil or petroleum residues. Dealing with these contaminated materials has become an increasing concern and requires innovative technologies able to remove the pollution but offering as well guaranties on the efficiency and safety of the treated material. This paper proposes the assessment of a bioremediation process of polluted soils contaminated by oil. In partnership with scientists from INPL/INRA (French National Research Institute for Agronomy) and CNRS (French National Scientific Research Center) specialized in organic pollutants chemistry, agronomy and pedology, TOTAL E&P carried an experimental on a biopile process over 15 months. Thirty cubic meter of polluted soil (24 tons) were engineered on three concrete basement plots (3.2 x3 m) covered by a black tent to avoid meteoric water infiltration. In order to optimize bioremediation effects, fertilization was carried out, consisting of supplying agricultural fertilizers to reach a C/N/P ratio of 100/9/1. The soil was mixed with straw (15% v/v) to increase air diffusion, stimulate micro-organisms growth and improve the soil structure. Moreover water was periodically added to keep moisture content between 80 to 100 % of the water holding capacity of the soil. The treatment was assessed not only on the base of the total contaminant concentration but also on a fine chemical characterization and on an ecotoxicological point of view. The evolution of the composition of the pollutants was assessed through the 15 months of the experiment and completed with toxicity measurements on both leachates (Microtox®) and soil (plant germination and growth tests). Results showed that the total contaminant concentration was decreased by 72%. The main outcome of this experiment is to determine the ratio between the biodegradation rate of low molecular weight organic molecules and the one of macromolecules, which are significantly more difficult to biodegrade. The experiment also aimed at generating 30m3 of partially treated soil to evaluate its impact on the environment. The final objective is optimal re-use of soils polluted by hydrocarbons after treatment, in view of sustainable management of the soil resource.