Laboratory evaluation of a biodegradable surfactant for In Situ soil flushing

Abstract

Laboratory studies were performed to examine the removal of NAPL m‐xylene from porous media using a biodegradable 5% sodium lauroy/sarcosinate surfactant flushing solution (Hamposyl L‐30, Hampshire Chemical Corp., Nashua, NH). Vertical glass columns were packed with 0.6‐mm glass beads or washed sand and contaminated with m‐xylene. Columns were drained by gravity so that the media initially contained three phases: air, water, 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 solution, as opposed to an estimated 477 pore volumes required when flushing with water alone. Addition of surfactants caused decreases in interfacial tensions and therefore column dewatering that resulted in decreased flow rates through the unsaturated media. Effluent samples were acidified to induce phase separation via formation of water insoluble sarcosine acid, which was observed as a white waxy solid that contained 95.4% of the effluent m‐xylene in the solid phase. A biodegradable surfactant that, once used, can be separated from the effluent with the organic contaminant immobilized in the solid phase appears to be attractive for soil remediation purposes.