RF Stimulation of Air Channels During Air Sparging

The task of cleaning leakage from aging underground tanks along with surface spills of gasoline and other hazardous chemicals is of the utmost importance and falls to both federal and local agencies as wells as private parties. Traditional clean up and contaminant removal involves dig and treat methods that are costly and impractical for large contaminated sites. Less disruptive remediation techniques, such as air sparging, have become more attractive in the past decade. Air sparging, bioventing, soil vapor extraction (SVE), and other remediation techniques that use air injection into soil can become very effective for VOC removal through volatilization and bioremediation. However, these methods are limited by restricted airflow in soil. The majority of the injected air flows through narrow channels formed in soil that acts as mass transfer zones (MTZ). Diffusion of air between these channels could help the cleanup and increase the effective area of air injection wells. We propose the use of RF stimulation to expedite airflow and diffusion and control air channel formation. To study this effect, we modeled the saturated soil conditions for air sparging within a clear acrylic box filled with: (i) water as the medium and an inert dye as the diffusive matter, and (ii) water-saturated glass bead medium with air as the diffusive matter (air was injected through a PVC pipe placed at the center of the box. A relatively high power plane electromagnetic field was radiated through the saturated medium. This was made possible using an idealized monopole antenna connected to an amplifier matching network. The oscillating electric field oscillates the dipole water molecules and the effects of the electric field on air channel formation in the second case (i.e., glass-bead medium) were studied. The stimulation of the water increases diffusion of air between air channels and enhances channel formation. The effect of this RF stimulation of air diffusion in the space surrounding the air channels is also studied