Surfactant-enhanced ozone sparging for removal of organic compounds from sand

Abstract

An innovative surfactant-enhanced ozone sparging (SEOS) technique was developed in this study. The synergistic effect of simultaneous surfactant and ozone application on the removal of organic contaminants in an aquifer during air sparging was investigated. Using laboratory-scale one- and two-dimensional physical models packed with water-saturated sand, air sparging and ozone sparging were implemented either at high or low level surface tension of the groundwater. A water-dissolved chemical (fluorescein sodium salt) and a nonaqueous phase liquid (n-decane) were used as the representative contaminants. Sodium dodecylbenzene sulfonate was used for sparging experiments at low level surface tension. Ozone sparging at low surface tension (SEOS) was found to be the most efficient process for the removal of organic chemicals, among AS (air sparging at high surface tension), SEAS (surfactant-enhanced air sparging, air sparging at low surface tension), and OS (ozone sparging at high surface tension), based on the results from a one-dimensional column study. Two-dimensional model experiments also showed that SEOS is more efficient than conventional AS processes. The increased air saturation and sparging influence zone achieved by surfactant application, and the oxidative power of ozone are responsible for the enhanced removal of contaminants from the aquifer. Considering that the application of conventional AS is limited to volatile contaminants, and that OS has a very narrow influence zone, SEOS can be an useful option for the removal of contaminants of low vapor pressures from an expanded zone of influence.