Comparison of residual NAPL source removal techniques in 3D metric scale experiments

Abstract

This study compared four treatment techniques for the removal of a toluene/n-decane as NAPL (Non Aqueous Phase Liquid) phase mixture in identical 1 cubic meter tanks filled with different kind of sand. These four treatment techniques were: oxidation with persulfate, surfactant washing with Tween80®, sparging with air followed by ozone, and thermal treatment at 80°C. The sources were made with three lenses of 26×26×6.5cm, one having a hydraulic conductivity similar to the whole tank and the two others a value 10 times smaller. The four techniques were studied after conditioning the tanks with tap water during approximately 80days. The persulfate treatment tests showed average removal of the contaminants but significant flux decrease if density effects are considered. Surfactant flushing did not show a highly significant increase of the flux of toluene but allowed an increased removal rate that could lead to an almost complete removal with longer treatment time. Sparging removed a significant amount but suggests that air was passing through localized gas channels and that the removal was stagnating after removing half of the contamination. Thermal treatment reached 100% removal after the target temperature of 80°C was kept during more than 10d. The experiments emphasized the generation of a high-spatial heterogeneity in NAPL content. For all the treatments the overall removal was similar for both n-decane and toluene, suggesting that toluene was removed rapidly and n-decane more slowly in some zones, while no removal existed in other zones. The oxidation and surfactant results were also analyzed for the relation between contaminant fluxes at the outlet and mass removal. For the first time, this approach clearly allowed the differentiation of the treatments. As a conclusion, experiments showed that the most important differences between the tested treatment techniques were not the global mass removal rates but the time required to reach 99% decrease in the contaminant fluxes, which were different for each technique.

Removal of NAPL from columns by oxidation, sparging, surfactant and thermal treatment

“…At the column scale the efficiencies among oxidation sparging and surfactant were quite similar in this study. The main objective was to identify the main limiting factors, as these factors will need to be addressed in detail to upscale the treatment at the larger pilot scale (Atteia et al, 2017).…”

Guidelines for surfactant selection to treat petroleum hydrocarbon-contaminated soils

“…Nevertheless, little is known about gasoline and diesel (Yan et al 2016 ). In addition, previous works about petroleum hydrocarbons analyzed the efficacy of surfactants only for total petroleum hydrocarbon (TPH) removal (Baziar et al 2013 ; Chevalier 2003 ; Deshpande et al 1999 ; Karthick and Chattopadhyay 2017 ; López et al 2004 ; Vreysen and Maes 2005 ; Zhu et al 2005 ) or for representative compounds such as toluene, decane, or dodecane (Atteia et al 2017 ; Jousse et al 2017 ; Pennell et al 1993 ). Surfactant selection is an important aspect to consider because each soil flushing process is different since it depends on the soil and the contaminants as no two contaminant–soil combinations are the same.…”

Comparison of theory and experiment for NAPL dissolution in porous media

“…Under the action of capillary forces, this contamination leads to the formation of NAPL blobs or ganglia trapped in the soil (Hunt et al, 1988). The assessment, design and implementation of efficient cleanup and remediation strategies for systems containing residual NAPL are of great importance for environmental and earth sciences research (National Research Council (NRC), 2005;Mainhagu and Brusseau, 2016;Atteia et al, 2017).…”