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This paper presents a general numerical model able to simulate both organic pollutants migration (3-phase compositional flows, mass transfer, transport) in soils and aquifers and decontamination techniques such as pumping, skimming, venting, hot venting, steam injection, surfactant injection and biodegradation. To validate the simulator, a 3-D experiment in a large pilot (25 m × 12 m × 4 m) was carried out. A total of 0.475 m3 of diesel oil was injected into the pilot, and numerous in-situ measurements were performed to determine pollutants location and concentrations within the vadose and saturated zones. Prior to the pilot test, a predictive simulation computed the extent of the contaminated zone and the oil saturations. Numerical results showed good agreement between experiment and simulation. To demonstrate the simulator abilities to improve remediation operations, a soil vapor extraction (venting) of weathered gasoline in the vadose zone under a service station was simulated. Fourteen wells were drilled on the site and extraction took nine months. The simulation closely matches the field data. Further simulations show the possibility of venting optimization for this site. Introduction Groundwater contamination by organic compounds such as hydrocarbons or chlorinated solvents has become a major environmental concern. To help in understanding of the complex phenomena associated with the migration of non-aqueous-phase liquids (NAPL) and the design of remediation operations. specific numerical tools have been introduced. Understanding the evolution of NAPL in the subsurface requires knowledge of the migration of the contaminants (advection and dispersion) in both the vadose and saturated zone, transfer of components from NAPL to water and gas phases. Prediction of long-term evolution of the contamination may also require knowledge of interactions between organic pollutants and the porous matrix and biodegradation of both dissolved pollutants and residual NAPL trapped in the pores. Good comprehension of the above mechanisms will allow numerical simulators to be efficient tools for risk assessment purposes. Remediation processes aimed at removing NAPL from the subsurface. Different technologies are available or under development:–direct mobilization of NAPL, e.g. pumping, surfactant injection;–partitioning of contaminants from either the aqueous phase or oil phase into the gas phase, e.g. in situ stripping, vacuum extraction (venting), steam injection;–biodegradation of dissolved pollutants and of residual NAPL. While these various methods of remediation have been studied on the laboratory scale and have been used in field conditions, the design of an operation is often based on empirical guidelines or previous experience. Use of a comprehensive numerical tool may significantly increase our capability of optimizing such remediation operations. Numerous numerical models have been applied to oil-spill problems and decontamination processes as reviewed by Pinder and Abriola (1986), Corapcioglu and Panday (1991) and Panday et al. (1995). Compositional models developed to examine groundwater contamination scenarios include those by Abriola and Pinder, Corapcioglu and Panday, Forsyth and Shao, Sleep and Sykes, Falta et al., Le Thiez and Ducreux, and Unger et al. The goal of this work is to present two simulations cases performed with the SIMUSCOPP numerical model and the comparison between computed results and field observations. P. 723

Présenté par Ghislain de Marsily RésuméL'objectif de ce travail a été de développer un module innovant de biodégradation des chloroéthènes, fondé sur une triple approche biologique, thermodynamique et mécanistique. Le schéma de biodégradation proposé repose sur le postulat suivant : à chaque endroit de l'aquifère, un mécanisme de dégradation est dominant, celui qui implique l'accepteur d'électrons le plus énergétique. La sélection du mécanisme de biodégradation actif est ainsi fonction de la concentration des accepteurs d'électrons. Les cinétiques utilisées correspondent à des cinétiques de type Monod, modifiées pour prendre en compte l'influence possible de tous les composés présents sur la biodégradation d'un composé organique donné. Le modèle numérique développé a été appliqué à un cas test simple présenté dans cet article.

Once previous industrial activity has ceased, brownfields are found in urban and suburban environments and managed in different ways ranging from being left untouched to total reconversion. These situations apply to large surface areas often impacted by residual diffuse pollution. Though significant and preventing any sensitive use, residual contamination does not necessarily require treatment. Moreover, conventional treatments show their technical and economic limits in these situations and gentle remediation options such as phytomanagement might appear more relevant to the management those sites. Thus, these sites face up two major issues: managing moderate contamination levels and providing an alternative use of economic interest. This work proposes to assess a management strategy associating the phytoremediation of organic pollution along with the production of biomass for energy generation production. A 16-week controlled growth experiment was conducted on a soil substrate moderately impacted by multiple pollution, by associating rhizodegradation with Medicago sativa or biomass production with Robinia pseudoacacia or Alnus incana in monocultures. The effect of a microbial inoculum amendment on the performances of these treatments was also evaluated. Results showed total hydrocarbons (TH), and to a lesser extent polycyclic aromatic hydrocarbons (PAH), concentrations decreased over time, whatever the plant cover. Good biomass production yields were achieved for both tree species in comparison with the control sample, even though R. pseudoacacia seemed to perform better. Furthermore, the quality of the biomass produced was in conformity with the thresholds set by the legislation concerning its use as a renewable energy source. This work is included in the scientific program of the GISFI research consortium dedicated to the knowledge and the development on remediation technologies for degraded and polluted lands (Groupement d'Intérêt Scientifique sur les Friches Industrielles -http://www.gisfi.univ-lorraine.fr).