Influence of wettability on the recovery of NAPLs from alluvium

The physicochemical characteristics of five nonaqueous phase liquids (NAPLs) recovered from contaminated alluvial aquifers are presented. The five include two chlorinated degreasing solvents, one chlorinated dry-cleaning solvent and two weathered fuel hydrocarbons. In addition to density, viscosity, and interfacial tensions, the equivalent alkane carbon number (EACN), spreading coefficients and Amott-Harvey and USBM wettability indices with respect to alluvial aquifer materials are used as a means to characterize three of these NAPLs. Experimentally measured spreading coefficients of four of these NAPLs illustrate that field NAPLs can have positive initial spreading coefficients. Furthermore, capillary desaturation curves for two NAPLs with alluvial aquifer material collected from the NAPL zone are presented as an additional and important means to infer the practical implications of the wetting characteristics on the efficacy of NAPL recovery. The results from the wettability and capillary desaturation experiments show that these NAPLs are mixed-wet to oil-wet when measured in the alluvium from their respective field sites. Furthermore, these results indicate that the displacement of NAPLs from soils by water is more difficult for mixed-wet or oil-wet soils than it is for water-wet or weakly water-wet soils. Finally experimental data indicate that adding anionic surfactants to the water shifts the wettability toward water-wet and makes the NAPL easier to displace and recover.