Radio Frequency Heating for Soil Remediation

Abstract

Radio frequency heating (RFH) is a technology that increases the cost-effectiveness of a variety of site remediation technologies by accelerating the rate of contaminant removal. Heating makes the physical, chemical, and biological properties of materials such as contaminants, soil, and groundwater more amenable to remediation. RFH brings controlled heating to the subsurface, enhancing the removal of contaminants by soil vapor extraction (SVE), groundwater aeration (air sparging), bioremediation, and product recovery. The results presented are from a bench-scale study and a field demonstration that both used RFH to enhance the performance of SVE. The bench-scale study performed on PCE-contaminated soil revealed an increase, by a factor of 8, in the removal rate when RFH was used to heat soil to 90 °C. The application of RFH for a three-week period at a former gasoline station near St. Paul, MN, resulted in raising the ambient soil temperature from 8 °C to 100 °C in the immediate vicinity of the RFH applicator and to 40 °C 1.5 m (5 ft) away. Most significantly, the use of an integrated RFH/SVE system achieved an overall 50% reduction in gasoline range organics (GRO) in soil over a two- to three-month period. The discussion includes applications of RFH for enhancing bioremediation and product recovery.

Microwaves in soil remediation from VOCs. 1: Heat and mass transfer aspects

“…In particular, in situ treatments are possible using electrical energy, radio fre-Ž quencies, and steam injections Buettner and Daily, 1995;Price et al, 1997;Regan et al, 1995;Hyman and Bagaasen, . 1997 .…”

“…RF , as ancillary process to be added to SVE, has been pro-Ž . posed by Price et al 1997 to clean by in situ operations a gasoline polluted zone of Minnesota. RF energy was deliv-Ž ered by an antenna applicator 27.12 MHz frequency and 5 .…”

In Situ Thermal Remediation for Source Areas: Technology Advances and a Review of the Market From 1988–2020

“…In 1989, the first patents for thermal conductive heating (TCH) use for remediation were filed by Shell Oil Company (Vinegar and Stegemeier 1991; Vinegar et al 1993), which were later donated to the University of Texas and then licensed in 2000 for commercial application. The first trial of radio frequency heating (RFH), where radio waves are applied at authorized frequencies of 6.78, 13.56, 27.12, or 40.68 MHz (MHz) (Price et al. 1999), occurred in the late 1980s at the Volk Air National Guard Base (U.S. Army Corps of Engineers [USACE] 2009). The concepts of using smoldering combustion reactions for remediation also began in academia at the University of Edinburgh in 2005. The first smoldering field projects were initiated in the late 2000s.…”

Optimizing the Environmental Performance of In Situ Thermal Remediation Technologies Using Life Cycle Assessment

“…In this study, we investigate the environmental impacts of the four in situ thermal remediation methods most often applied at field scale (Kingston et al 2010). These are: (1) Steam Enhanced Extraction (SEE) (Davis 1998) which heats the subsurface by the injection of steam, (2) In Situ Thermal Desorption (ISTD) (LaChance et al 2006;Heron et al 2009) which applies thermal conduction heating to the subsurface through the use of heater elements, (3) Electro-Thermal Dynamic Stripping Process (ET-DSP™) (McGee 2003) which is included as a representative for Electrical Resistance Heating (ERH) methods, and (4) Radio Frequency Heating (RFH) (Price et al 1999) that heats the soil by applying energy with radio frequency. A soil vapor extraction system is included in all technologies to extract the contaminated vapors, which are subsequently treated above ground.…”