AN INNOVATIVE METHOD FOR CLEANING UP CONTAMINATED GROUNDWATER

For the past 20 years a sustained effort has been underway to clean up contaminated groundwater. Many new methods and technologies have evolved to achieve the goal of timely and cost-effective remediation of contaminated aquifers.

The authors have developed a new method for a more efficient clean up of contaminated groundwater. It represents a combination of the successful technologies of air stripping, air sparging, soil vapor extraction, and in situ bioremediation. The new method, tentatively called, KC InWell Air Stripping (KCIWAS) eliminates most of the limitations of these methods, thereby making it a faster, cheaper, and more versatile method.

KCIWAS method is a self-contained clean up, treatment, and disposal method-all of which occur in the subsurface, obviating the need of costly above-ground treatment to bring the contaminants' concentration down to levels required by regulators for its release into sewer. The method is particularly suitable for use at ecologically sensitive sites and where sufficient space on the ground may not be available.

The method utilizes air sparging by injecting compressed air, pumped into the bottom of the well, to remove the contaminants. A submersible pump, placed at well bottom, forces the contaminated groundwater up toward the top of the well and above the groundwater table, leading into a water dispersion device. As the contaminated groundwater leaves the dispersion device, additional cleanup occurs by air stripping. In addition, pumping fresh air into the subsurface enhances bioremediation by providing oxygen for growth and survival of the biodegrading microorganisms.

Field and laboratory tests were conducted to evaluate the method and test its efficacy. Preliminary on-site test at an industrial facility in Minnesota showed a significant reduction in concentration of tetrachloroethene (PCE). In a monitoring well, PCE was found to decrease from 2,700 to 240 ppb (about 90%) in 13 days. Dissolved oxygen levels also showed a marked recovery from 1 ppm to 8 ppm during the same period.