Chanat Chokejaroenrat, Advisor: Dr. S.D. Comfort. ABSTRACT Groundwater beneath the former Nebraska Ordnance Plant (NOP) is contaminated with the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). Laboratory and pilot-scale experiments were performed to quantify the efficacy of permanganate to remediate RDX-contaminated groundwater. Laboratory investigations determined the effects of quenching agents, pH, and temperature on RDX destruction kinetics and reaction products. Batch experiments showed that RDX destruction kinetics and mineralization increased with increasing MnO4- concentrations but RDX was less reactive than other NOP groundwater contaminants (i.e., TNT and TCE). While high concentrations of permanganate (>5000 mg L-1) are typically needed to oxidize RDX, significantly lower concentrations (100-500 mg L-1) are effective at sub-boiling temperatures (60ºC). To identify possible intermediates and end products, various quenching agents (MnSO4, MnCO3, H2O2) were evaluated. Results showed quenching agents influenced sample pH and product distribution. Based on laboratory results and the lack of readily identifiable intermediates, we believe the first step in the RDX-MnO4- reaction is rate-limiting and proposed two possible RDX degradation pathways. The first mechanism is favored at neutral pH and involves removal of a hydride from the methylene carbon followed by hydrolysis and decarboxylation. This same three-step cycle of oxidation, hydrolysis, and decarboxylation would continue leading to N2O and CO2. The second mechanism is similar to the previously reported hydrolysis pathway where proton abstraction from the methylene hydrogen occurs causing a nitro group to be released and a double bond formed on the triazine ring. Subsequent reactions ultimately lead to mineralization end products (N2O, CO2, NO3-, and H2O). 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 fed into two injection wells. We then sampled groundwater bi-weekly 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 could be used for in situ chemical oxidation of RDX-contaminated groundwater.