Surfactant enhanced in situ remediation of LNAPL contaminated aquifers:: Large scale studies on a controlled experimental site

A central problem in a real case remediation of an oil contaminated site is the knowledge of the volume and the extent of the pollution. As the estimation of the mass balance, usually based on some point measurements, presents a large range of uncertainty, controlled experisites constitute essential research tools. The objective of SCERES (Controlled Experimental Site for Water and Soil Remediation Research) is to test techniques for both pollution quantification and in situ remediation of light non-aqueous phase liquid (LNAPL) contaminated aquifers and soils. This paper reports results of experiments conducted on the experimental site SCERES and describes two techniques of surfactant flushing for the recovery of trapped diesel oil: an infiltration from the soil surface for the vadoze zone treatment and injections in depth for the capillary fringe treatment. Despite a satisfying mass balance, we underline some complex phenomena which influence the flow of fluids such as surfactants and mobilized oil in saturated and unsaturated porous media, in particular, the effect of surfactant agglomeration on oil removal efficiency. This research work also highlights some problems especially those linked with the confinement of the heterogeneous oil impregnation body.