Surfactant Enhanced Recovery
Surfactant enhanced recovery increases the mobility and solubility of the contaminants sorbed to the saturated soil matrix. Surfactants (i.e., surface-active agents) are the primary ingredients of many soaps and detergents. Surfactant-enhanced recovery injects surfactants into contaminated groundwater. A typical system uses an extraction pump to remove groundwater downstream from the injection point. The extracted groundwater is treated aboveground to separate the injected surfactants from the contaminants and groundwater. Once the surfactants have separated from the groundwater they are re-used. Contaminants must be separated from the groundwater using one of many treatment methods. The surfactants used are non-toxic, food-grade, and biodegradable.
Surfactant enhanced recovery is used most often where the groundwater is contaminated by dense nonaqueous phase liquids (DNAPLs). These dense compounds, such as trichloroethylene (TCE), sink in groundwater because they are heavier than water. They then act as a continuous source for contaminant plumes that can stretch for miles within an aquifer. These compounds may biodegrade very slowly. They are commonly found in the vicinity of the original spill or leak where capillary forces have trapped them.
Limitations and Concerns
Hydraulic control of the surfactant and contaminants must be maintained to prevent the spread of contamination.
Air emissions should be controlled at aboveground treatment.
Surfactant enhanced recovery is often used to complement conventional pump-and-treat systems for removing dissolved-phase DNAPL contamination.
A typical system removes and treats VOC-contaminated groundwater. It is used primarily for removing DNAPLs, although it could be used for removing other hydrocarbons, such as fuel.
Technology Development Status
Surfactant enhance recovery has been used in the oil industry for years. It is commercially available, although each surfactant should be matched with the contaminant.