LABORATORY EVALUATION OF A BIODEGRADABLE SURFACTANT FOR IN-SITU SOIL FLUSHING

Laboratory studies were performed to examine the removal of NAPL m-xyl ene from porous media using a biodegradable 5% sodium lauroyl sarcosin ate surfactant flushing solution (Hamposyl L-30, Hampshire Chemical Co rp., Nashua, NH). Vertical glass columns were packed with 0.6-mm glass beads or washed sand and contaminated with m-xylene. Columns were dra ined by gravity so that the media initially contained three phases: ai r, wafer, and m-xylene. Removal of m-xylene was primarily by enhanced solubilization. Recovery of 95% of residual m-xylene from washed sand was obtained with an average of 43.2 pore volumes of surfactant soluti on, as opposed to an estimated 477 pore volumes required when flushing with water alone. Addition of surfactants caused decreases in interfa cial tensions and therefore column dewatering that resulted in decreas ed flow rates through the unsaturated media. Effluent samples were aci dified to induce phase separation via formation of water insoluble sar cosine acid, which was observed as a white wavy solid that contained 9 5.4% of the effluent m-xylene in the solid phase. A biodegradable surf actant that, once used, can be separated from the effluent with the or ganic contaminant immobilized in the solid phase appears to be attract ive for soil remediation purposes.