| Numerous remediation technologies, such as pump-and-treat and air sparging, have demonstrated mixed results in treating contaminated soil and groundwater in subsurface geologic environment. It has become apparent that many of these generally accepted technologies, reach contamination reduction asymptote before the desired site cleanup levels are achieved.; The research led to the development of an effective remediation method, named the ART technology. The ART technology combines in situ air stripping, air sparging, soil vapor extraction, enhanced bioremediation/oxidation and subsurface circulation—all within an innovative wellhead system. The technology is designed to accommodate a four-inch well and is cost effective when compared with other remediation technologies.; The air-sparging component results in lifting the groundwater table. This lifting of the groundwater in the well causes a net reduction in head at the well location. Vacuum pressure is applied atop of the well point to extract vapors from the subsurface. The negative pressure from the vacuum extraction results in water suction that creates additional groundwater lifting (mounding). A submersible pump is placed in the well to recirculate groundwater to the top for downward discharge through a spray head. The water cascades down the interior of the well; similar to what occurs in an air-stripping tower. Enhanced stripping via air sparging occurs simultaneously, causing the well to act as a subsurface air-stripping tower. The pumped and stripped, highly oxygenated water flows down well annulus and over the “mounded” water surface back in to the aquifer which creates a circulation zone around the well to further enhance cleanup.; The ART system has been implemented at several sites nationwide and has achieved significant reductions in contaminant concentrations in a short time. Specifically, at one of the sites, concentrations of tetrachloroethene (PCE) decreased from 2,700 to 240 μg/L, or by an average of approximately 90% in 13 days. In three months, the concentrations dropped further to 79 μg/L, which is within the range of background levels. Other test sites where this system has been implemented, have exhibited similar reduction trends in complex subsurface geologic environments. |
