Task 17 - Use of Acoustic Energy and Humic Acids to Mobilize DNAPLS from the Subsurface

Contamination of the subsurface with dense nonaqueous-phase liquids (DNAPLs) is common throughout the US, especially at Department of Defense (DOD) and Department of Energy (DOE) sites. These compounds are difficult to remove, as they are poorly soluble in water and tend to stay in pools or sorb strongly to aquifer materials because of their cohesiveness and nonpolarity. Pump and treat is a technology application that offers remediation and contaminant plume containment. However, because of poor mobility and limited volubility, DNAPLs can persist as a contaminant source for years, even decades. Enhanced removal of these compounds from the subsurface requires methods to reduce cohesiveness and improve volubility. Acoustic energy introduced to the subsurface has the potential to disrupt the DNAPL pool and improve mixing. Even with this major improvement, remediation of the contamination maybe slow because of poor volubility. Surfactant compounds can also reduce cohesiveness and improve apparent volubility through the formation of micelles containing DNAPL. Commercial surfactants are subject to problems: they are expensive and toxic, sorb to aquifer materials, and exert a biochemical oxygen demand. Nonpolar compounds (DNAPLs) can be sorbed. Humic acids are poorly biodegradable, generally not well adsorbed to aquifer materials, and nontoxic. The combination of acoustic energy and humic acids has high potential for faster, less expensive remediation of subsurface DNAPL contamination when used to enhance pump-and-treat methods or in situ bioremediation