| The remediation of aquifers contaminated by nonaqueous phase liquids (NAPLs) is a national priority. A novel technique for aquifer remediation using surfactant-alternating-gas foam (SAGF) was investigated with micromodels. Air flow was introduced to conventional surfactant solution flow (Sodium C 14–16 Olefin Sulfonate) to enhance the poor flooding efficiency of surfactant flushing. The qualitative and quantitative investigations on SAGF behaviors were conducted by both micro-scale visualization and quantification. Micromodel investigations help us understand pore-scale behavior of NAPL displacement as well as macro-scale properties during flooding.; SAGF displaced a higher amount of residual trichloroethylene (TCE) as compared to surfactant solution alone. The SAGF flooding removed 99.4% of the residual TCE with just 8 pore volumes of surfactant solution, while surfactant flushing removed about 41.4% with 25 pore volumes of the same surfactant solution. Enhanced displacement mechanisms were addressed to explain the higher efficiency. SAGF flow produced viscous forces 60 times greater than those of surfactant flow alone. Residual TCE blobs were broken into smaller blobs by the high viscous forces of SAGF, which were then more easily dissolved into micellar solution. Physicochemical factors affecting SAGF flooding, such as gas fraction, surfactant solution, pore structure, apparent SAGF viscosity and SAGF mobility, were investigated to better understand SAGF behaviors in porous media. SAGF remediation technology achieved high NAPL removal efficiency via a displacement strategy without lowering the interfacial tension to an ultralow level and leading to vertical migration of TCE. The results of this study show that the SAGF technology appears to be a promising groundwater remediation technology. |
