WorldWide Drilling Resource®

26 MARCH 2020 WorldWide Drilling Resource ® Using Electrical Resistance Heating for Groundwater Remediation Compiled by Bonnie Love, Editor, WorldWide Drilling Resource ® Electrical resistance heating (ERH) has been a widely-used process to clean contaminated soil and groundwater for years. it works by using electricity and it’s very effective. it starts by installing electrodes into recovery wells drilled throughout a contaminated site. An electrical current is passed through the soil and between the electrodes, causing the soil and fluids to heat up. This causes the underground contaminants and water to evaporate, creating in situ steam and vapor. The vapors, steam, and NAPl (nonaqueous phase liquids) are recov- ered to the surface using a vacuum. ERH systems can be used at any depth and used in both the vadose (underground water above the water table) and sat- urated zones. The electrodes are installed with conventional drilling rigs, but can also be done using horizontal or angular drilling techniques. The horizontal spacing between electrodes is typically between 14-24 feet. Soil with a high natural organic carbon content may slow or prevent recovery of some organic contaminants. The ERH process for remediation purposes was developed by the Department of Energy and Battelle using six-phase electricity and a hexagonal electrode array. However, this led to cold and hot spots in the targeted location. Three-phase power and tri- angular electrode arrays are more commonly used today. This technique was successfully used at the Camelot Superfund Site in West Fargo, North Dakota. The site of a former dry cleaning facility, the soil and groundwater were contaminated with tetra- chloroethylene, trichloroethylene, and their degradation products. Approximately 13,800 cubic yards of soil was treated over a nine- month period. Using 56 different electrode and vent assemblies, along with a network of horizontal vapor extraction wells, approxi- mately 5188 pounds of contaminated mass was extracted. The Environmental Protection Agency sampled the area and confirmed the process reduced the groundwater concentrations of contamination 99.98% while the soil concentrations were reduced 99.96-100%. in addition to being a safe and effective method for cleaning contamination, the ERH cleanup process usually takes between six and nine months as opposed to conventional treatment methods which typically takes years. Photo of the Camelot Superfund Site work courtesy of TerraTherm, a Cascade Company. WTR