TCE Remediation in Groundwater Using Recirculating Wells Coupled with Permanganate Injection

A pilot test utilizing a recirculating groundwater remediation well (RGRW) in conjunction with permanganate injection was conducted in early 2003 down gradient from a source area in the Pacific Northwest. The purpose of the field study was to evaluate the implementability and effectiveness of paired technologies to mitigate trichloroethene (TCE) and other volatile organic compounds in groundwater. Prior to field testing, a numerical groundwater model evaluated the horizontal and vertical extent of influence as a result of groundwater circulation within the well. In a dual screen RGRW, the bottom screen extracted water and the upper screen discharged it back to the aquifer. A 40% (weight/volume) sodium permanganate solution was injected into the extracted groundwater prior to discharge into the aquifer. The final concentration of permanganate after mixing was less than 0.01%. Pre- and post-treatment analytical results from the monitoring wells were evaluated to monitor the performance of the test. The reduction in TCE levels in groundwater ranged from 94% to 100% in shallow monitoring wells (45 feet below ground surface [bgs]) and 4% to 60% in intermediate and deep wells (60 and 80 feet bgs, respectively) following one week of operation with permanganate injection. After two months of successful operation of the pilot test, the system was progressively converted into a full-scale remediation system by installing six additional RGRWs of similar design and operation.