In 1993, the Air Force constructed the Source Recovery System at OU-2. To date, it has collected more than 40,000 gallons of solvent from the site. But engineers estimate that there are about 5,000 gallons of solvent still underground. The new technology will allow the Air Force to recover most, if not all, of that remaining solvent. Why surfactants work.
Capillary pressure is the same force that draws water into a sponge.
Capillary pressure, directly influenced by interfacial tension, traps the solvent globules in the soil. According to Ginn, the key to removing the residual solvent is to reduce the capillary pressures. That's where surfactants come in. Surfactants reduce the interfacial tension between the soil and the solvent, which in turn reduces the capillary pressures and frees the trapped solvent globules. The solvent can then be removed from the groundwater using the Source Recovery System.