Influence of particle size distribution and wettability on the displacement of LNAPL in saturated sandy soils

Abstract

Immiscible displacement processes are of key importance in remediation actions of light nonaqueous phase liquid (LNAPL) contaminated soil and groundwater. LNAPLs remain trapped in soil pores after a spill or flushing process due to the interplay of viscous, gravity, and capillary forces. In this research immiscible displacement tests were conducted in homogenous and heterogeneous sand samples. Also, the influence of fine content, mineralogy, and wettability was evaluated by testing mixtures of coarse sand with silt, zeolite, bentonite, and hydrophobic sand. Obtained results highlight the importance of pore-scale heterogeneities on the resulting displacement pattern in macroscopically homogeneous samples, and show the preferential accumulation of LNAPLs at the interfaces between different materials in heterogeneous samples. Fine particle content shows no important consequences on residual saturation but significantly changes relative permeability. In addition, the presence of hydrophobic particles also modifies hydraulic conductivity and residual LNAPL saturation. Finally, relative permeability models were fitted to experimental data in order to estimate relative permeability of tested samples.