To evaluate the efficacy of permanganate to remove RDX under field conditions, a pilot-scale demonstration was performed in a 9 m by 15 m well field.Groundwater was extracted from a center extraction well, spiked with permanganate and bromide, and fed into two injection wells. Groundwater was then sampled biweekly for 8 weeks in monitoring wells down gradient of the injection zone. Results showed that RDX concentrations decreased 73 to 80% following injection. Despite problems encountered in getting the permanganate uniformly distributed across the injection zone, pilot-scale results provide proof-of-concept that permanganate can be used for in-situ chemical oxidation of RDX-contaminated groundwater.

Groundwater beneath the former Nebraska Ordnance Plant (NOP) is contaminated with the explosive hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) and trichloroethene (TCE). Previous treatability experiments confirmed that permanganate could mineralize RDX in NOP aquifer material. The objective of this study was to determine the efficacy of permanganate to transform RDX in the field by monitoring a pilot‐scale in situ chemical oxidation (ISCO) demonstration. In this demonstration, electrical resistivity imaging (ERI) was used to create two‐dimensional (2‐D) images of the test site prior to, during, and after injecting sodium permanganate. The ISCO was performed by using an extraction‐injection well configuration to create a curtain of permanganate. Monitoring wells were positioned downgradient of the injection zone with the intent of capturing the permanganate‐RDX plume. Differencing between ERI taken preinjection and postinjection determined the initial distribution of the injected permanganate. ERI also quantitatively corroborated the hydraulic conductivity distribution across the site. Groundwater samples from 12 downgradient wells and 8 direct‐push profiles did not provide enough data to quantify the distribution and flow of the injected permanganate. ERI, however, showed that the permanganate injection flowed against the regional groundwater gradient and migrated below monitoring well screens. ERI combined with monitoring well samples helped explain the permanganate dynamics in downgradient wells and support the use of ERI as a means of monitoring ISCO injections.