In Situ Treatment of Chlorinated Volatile Organic Compounds (CVOCs) With a Deep Active Configuration Horizontal Reactive Treatment Well (HRX Well®)

ABSTRACT

The Horizontal Reactive Treatment Well (HRX Well®) consists of a large‐diameter dual‐screened horizontal well that is oriented in the general direction of groundwater flow and contains an appropriate treatment media in the center cased section. Contaminated groundwater enters the upgradient screen, is treated in the well within the cased segment, and is then discharged back to the aquifer through a downgradient screen. Previous HRX Wells have been operated in a passive configuration, where groundwater preferentially flows into the HRX Well due to hydraulic conductivity contrasts between the aquifer and the well. Herein, the results of the first field demonstration of an HRX Well designed with a pump to enhance flow through the well (termed active configuration) are presented. Based on the results of treatability tests and design modeling, a dual‐screen 8‐inch diameter HRX Well was constructed. The total well length was 1190‐ft long with a target treatment depth of 125‐feet deep. The inlet and outlet screens were both 40 ft in length, and the available treatment segment length was 65 ft. The treatment segment was equipped with multiple removable cartridges containing zero valent iron (ZVI) and granular activated carbon (GAC) to treat chlorinated volatile organic compounds (CVOCs). The HRX Well operated with minimal operation and maintenance activity for 2.3 years, and a treatment efficiency of 100% for target CVOCs was maintained throughout the performance period. The estimated average treatment zone width was at least 70 ft, and approximately 55,000 gallons of groundwater were treated. Overall, this study further confirms the HRX Well concept and highlights the benefits and implementability of the active configuration, which increases treatment zone size and allows the ability to prescribe specific flow rates.