Stockpiles of aging, off-spec, or other military munitions containing energetic formulations pose a health and safety risk to humans and the environment. This research is the first report demonstrating electrochemical demilitarization of solid Composition B (CompB; HMX/RDX/TNT) and nitrocellulose (NC) fines. The process combined alkaline hydrolysis with cathode surface reactions in a divided electrochemical cell configuration. The constituents of CompB were degraded (>95 %) to simple end products consisting primarily of NO2-, formaldehyde, and residual color. The latter two compounds were shown to be readily amenable to an UV/H2O2 treatment as a potential polishing step. NC fines were hydrolyzed to NO2-, NO3-, NH4+ and unspecified total organic carbon (TOC) and total Kjeldahl nitrogen (TKN), with minimal accumulation of free cyanide. For both energetics, the degradation kinetics were improved by heating the system to 50 degrees C. The estimated cost of treatment at the elevated temperature, including chemicals and energy, was <$0.05 per g for CompB and between $0.18 and $0.29 per g for NC, depending on the size cutoff for residuals (>5 and >1.5 mu m, respectively). These results provide proof-of-concept that electrochemical processes for treating solid energetic materials may be an effective approach for safe and efficient demilitarization treatment trains for military munitions.

A two-stage anaerobic-aerobic membrane bioreactor (MBR) effectively treated synthetic and real munition constituent wastewaters consisting of various combinations of traditional (2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)) and insensitive (nitroguanidine (NQ), 2,4-dinitroanizole (DNAN), 3-nitro-1,2,4-triazole-5-one (NTO)) explosives, as well as the oxidants perchlorate (ClO4-) and nitrate. Microbial community dynamics in the anaerobic and aerobic MBRs were analyzed. In the anaerobic MBR, Pleomorphomonas spp. and Saccharimonadales dominated and established within the community network. Increased ClO4- promoted Pleomorphomonas, Propionibacteriaceae, and Christensenellaceae; these populations also thrived during IMX-101 (NQ, NTO, DNAN) treatment. Switching the main carbon feed to the ANO MBR from fructose to invert sugar increased NQ biotransformation with a corresponding increase of unknown Propionibacteriaceae. Coincident with the feed of actual IMX-104 (RDX, NTO, DNAN) wastewater, a unique group of Rhodococcus erythropolis proliferated, and high levels of xenA, xenB, and nitronate monooxygenase orthologs were detected, which could be associated with degradation of insensitive high explosives and RDX. The aerobic MBR showed high percentages of Proteobacteria as the main phylum. Beijerinckiaceae most frequently dominated and formed a singular submodule, suggesting a unique role in the degradative process. Adding an NQ-oxidizing inoculum increased Reyranella spp., Leucobacter spp., and unknown Beijerinckiaceae which enhanced NQ degradation. Overall, minor microbial community shifts were driven by variations of munition wastewater compositions but the abilities of the MBRs to degrade munitions constituents was maintained even after individual or multiple constituents were absent from the feed for weeks and then re-added. This demonstrates the high resilience of the dual MBR system and may provide insights for performance optimization.

This research evaluated the cathodic electrochemical treatment of wastewater contaminated with energetic compounds, including "legacy" explosives octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), hexahydro-1,3,5-trinitro-s-triazine (RDX), and trinitrotoluene (TNT), as well as compounds insensitive munitions constituents, including 3-nitro-1,2,4-triazol-5-one (NTO), nitroguanidine (NQ), 2,4-dinitroanisole (DNAN). Rate constants and transformation products observed using electrochemical degradation performed under constant voltage (4 V) and constant current (0.5 A), as well as degradation via alkaline hydrolysis, were compared. Electrochemical degradation rate constants for all the energetics were greater than rate constants measured during alkaline hydrolysis. Degradation rate constants for individual energetics were generally similar to those observed in a mixture of all six compounds, with the exception of TNT (0.41 vs. 1.08 h-1). Many of the transformation products detected (e.g., HCHO, dinitrophenol (DNP), NH4+) evidenced further electrochemical degradation, but remained as residuals during alkaline hydrolysis. Utilizing 13C/15N labeled parent compounds, varying degrees of mineralization to 13CO2 and 15N2O were confirmed for RDX, NTO, and DNAN. The calculated electrical energy per order of removal (EEO) was generally lower under constant voltage compared to constant current conditions, and ranged from 2 Wh/L for TNT to 10 Wh/L for NTO. These results provide proof-of-concept data for cathodic electrochemical treatment of mixed energetics wastewater.

This study investigated the regenerability of anion exchange resins for per- and polyfluoroalkyl substances (PFAS), focusing on the interaction between regenerant composition and resin characteristics. The influence of salt type and concentration on PFAS solubility revealed a general decline in perfluorohexane sulfonate (PFHxS) solubility with increased salt concentrations, most strongly with KCl followed by NaCl and NH4Cl. Mixed solubility results were observed for perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS). Three resins – A592E and USA291597EPF (strong base resins) and USA21107 (weak base resin) – were evaluated using aqueous and organic solvent regenerants across multiple cycles. Batch regeneration experiments demonstrated that regeneration effectiveness was higher for short chain perfluoroalkyl carboxylates (PFCA) compared to long chain PFCA, followed by n:2 fluorotelomer sulfonates (FtS) and perfluoroalkane sulfonates (PFSA). Chloride-based salts regenerants were more effective, while the type of cation had minimal impact. Organic solvent regenerants outperformed aqueous solutions, with effectiveness increasing at higher percentages. For low organic solvent percentages, acetone demonstrated higher effectiveness compared to ethanol and methanol. Resin regenerability ranked as follows: USA291597EPF > A592E > USA21107. Flow through column studies confirmed the dependency of regeneration effectiveness on PFAS structural characteristics, with shorter chain PFCA demonstrating higher efficiency. The Lin and Huang model's parameters, time to desorb 50% of resin-associated PFAS (τ) and the column constant (kc), revealed two distinct desorption phases. The findings highlight the crucial role of regenerant composition in optimizing resin regeneration, offering valuable insights for developing more effective PFAS remediation strategies.

Aerobic cometabolism was first discovered more than 60 years ago and was the first biological approach to be evaluated for the treatment of chlorinated volatile organic compounds (cVOCs), such as trichloroethene (TCE). The discovery of reductive dehalogenation and subsequent anaerobic biostimulation and bioaugmentation processes supplanted cometabolism as the primary in situ biotreatment approaches for cVOCs beginning in the late 1990s. Anaerobic bioremediation has proven very effective for high concentration cVOC plumes. However, over the past few decades, dilute cVOC plumes (i.e., a few to a few hundred mu g/L) have increasingly been recognized as an issue of concern and several contaminants have emerged that are not subject to anaerobic treatment approaches and/or are present in groundwater at very low concentrations, but above relevant regulatory or health guidance concentrations. These compounds include methyl tert-butyl ether, 1,4-dioxane, N-nitrosodimethylamine, 1,2-dibromoethane, and 1,2,3-trichloropropane, among others. For these compounds, as well as many cVOCs (when present in groundwater at low concentrations), aerobic cometabolism is reemerging as a promising and cost-effective remedial approach. This paper reviews aerobic cometabolism and provides examples and guidance concerning its field application for a number of traditional and emerging contaminants.

The treatment of wastewater containing the new insensitive energetic formulation IMX-104, which consists of the legacy explosive RDX and insensitive high explosives (IHE), 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-triazole-5-one (NTO), was evaluated using a dual anaerobic-aerobic membrane bioreactor system. RDX and DNAN in the wastewater were completely degraded in the anaerobic MBR, with no observed production of common reduced daughter products (e.g., MNX, DNX or TNX for RDX and 2-ANAN, 4-ANAN, and DAAN for DNAN). NTO concentrations as high as 2 g L-1 were biotransformed predominantly to 3-amino-1,2,4-triazole-5-one (ATO) in the anaerobic MBR. The ATO degrading capacity of the aerobic MBR was exceeded at the high NTO concentrations, but subsequent polishing with 5 % sodium hypochlorite (∼4000 mg L-1 free chlorine) resulted in complete ATO removal. Electrochemical oxidation and UV/H2O2 treatment was also demonstrated to be effective for removal of residual ATO. The dual MBR system was fed a broader mixture of munitions constituents during some phases of operation, including HMX, TNT, nitroguanidine (NQ), perchlorate, and nitrate, and was observed to biodegrade these compounds even after a 90-day period when they were absent from the influent (i.e., during IMX-104 treatment). The dual MBR with sodium hypochlorite polishing proved to be highly effective for treatment of IMX-104 wastewater, as well as for removal of a variety of other munitions constituents.

Munition constituents (MC) in stormwater runoff have the potential to move these pollutants into receiving bodies at military installations. Here we present further evaluation of a passive and sustainable biofilter technology for removal of dissolved MC from simulated surface runoff by combined sorption-biodegradation processes under dynamic flow conditions. Columns were packed with MC sorbents Sphagnum peat moss and cationized (CAT) pine shavings with and without wood-based biochar. Some columns also received biodegradable polymers as a slow-release carbon source and MC degrading bacterial cultures. MC removal was greater under combined sorption-biodegradation conditions than under sorption only conditions, ranging from 2.5-fold for 2,4,6-trinitrotoluene (TNT) to >25-fold for hexahydro-1,3,5-trinitro-s-triazine (RDX). Biochar improved removal for some MC, which was attributed to it acting as a buffer by its ability to sorb/degrade these compounds, thus delaying their elution from the columns until the biodegradation activity increased. It was also found that labile carbon source availability, rather than microbial culture viability, was responsible for the apparent reduction in energetic removal over time. These results provide a foundation for further development of technologies for remediation of energetic compounds in military range stormwater runoff.

Microplastics (MPs) and nanoplastics (NPs) can affect microbial abundance and activity, likely by damaging cell membrane components. While their effects on anaerobic digestion are known, less is understood about their impact on microbes involved in contaminant bioremediation. Chlorinated volatile organic contaminants (CVOCs) such as tetrachloroethene (PCE) and explosives like hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) are common in the environment, and their bioremediation is a promising cleanup strategy. This study examined how polystyrene (PS) and polyamide 6 (PA6) MPs and NPs influence CVOC and RDX biodegradation. PS particles did not inhibit the CVOC-degrading community SDC-9, but PA6 MPs impaired the reductive dechlorination of trichloroethene (TCE) to cis-1,2-dichloroethene (cis-DCE), causing a “cis-DCE stall” with no further conversion to vinyl chloride (VC) or ethene. Only 45% of TCE was dechlorinated to cis-DCE, and Dehalococcoides mccartyi abundance dropped 1000-fold in 35 days with PA6 MPs. In contrast, neither PA6 nor PS MPs and NPs affected RDX biotransformation. These results highlight the significant impact of PA6 MPs on CVOC biodegradation and the need to consider plastic pollution in environmental management.

Residual munition constituents (MCs) generated from live-fire training exercises persist in soil and can migrate to groundwater, surface waters, and off-range locations. Techniques to mitigate this potential migration are needed. Since the MC hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) can be biodegraded, soil inoculation with RDX-degrading bacteria (i.e., bioaugmentation) was investigated as a means to reduce the migration potential of RDX. Metagenomic studies using contaminated soils have suggested that a greater diversity of bacteria are capable of RDX biodegradation. However, these bacteria remain uncultivated and are potentially a source of novel enzymes and pathways for RDX biodegradation. In situ soil cultivation of a novel soil array was used to isolate the uncultivated bacteria that had been inferred to degrade RDX. Approximately 10.5% of the bacteria isolated from the soil arrays degraded RDX by the aerobic denitration pathway. Of these, 26.5% were possibly novel species of RDX-degrading bacteria, based on 16S rRNA sequence similarity. Both cell encapsulation in hydrogels and coating cells onto granules of polymeric carbon sources were investigated as carrier/delivery approaches for soil inoculation. However, neither of these approaches could confirm that the observed RDX degradation was by the inoculated bacteria.

Per- and polyfluoroalkyl substances (PFAS) are synthetic organofluorine compounds known for their chemical and physical stability as well as their wide range of uses. Some PFAS are widely distributed in the environment, leading to concerns related to both environmental and human health. High temperature thermal treatment (i.e., incineration) has been utilized for PFAS treatment, but this requires significant infrastructure and energy, prompting interest in lower temperature approaches that may still lead to efficient destruction. Lower treatment temperatures, however, increase the potential for incomplete PFAS mineralization and formation of volatile organofluorine (VOF) products. Herein, we report the formation of novel VOF products that include chlorinated and brominated compounds during the thermal treatment of potassium perfluorohexane sulfonate (PFHxS), a representative perfluoroalkyl acid (PFAA). By comparing the gas chromatography-mass spectrometry (GC-MS) results of known VOF stocks to evolved VOF during thermal treatment of PFAS, the formation of perfluorohexyl chloride and perfluorohexyl bromide was observed when PFHxS was heated at temperatures between 275 and 475 degrees C in the presence of NaCl and NaBr, respectively. To our knowledge, this is the first report of chlorinated or brominated VOF products during thermal treatment of a PFAA. These findings suggest that a range of mixed halogenated VOF may form during thermal treatment of PFAS at relatively low temperature (e.g., 500 degrees C) and that these can be a function of salts present in the matrix.

One of the primary technologies currently being deployed for the removal of per- and polyfluoroalkyl substance (PFAS) from water is ion exchange (IX). For regenerable IX resins, concentrated PFAS in the resulting spent brine and/or still bottoms requires further treatment. This research demonstrated that PFAS in spent brine and still bottoms can be effectively degraded sonochemically at 1000kHz. Overall, PFAS degradation was negatively impacted by high total organic carbon (TOC) and residual methanol (MeOH) solvent (up to 50g/kg; 5% w:w), but was enhanced by the high chloride. The addition of caustic (up to 1N NaOH) partially mitigated the inhibition by TOC and MeOH. Sonochemical degradation of individual PFAS compounds resulted in significant mineralization to form inorganic fluoride, but small quantities of volatile organic fluorine species (VOF) were noted. This is believed to be the first report of sonochemical degradation of PFAS in ion exchange regeneration wastes, and indicates the possibility for the application of this technology as part of a complete PFAS capture and destruction treatment train.

2,4-Dinitroanisole (DNAN) is a main constituent in various new insensitive munition formulations. Although DNAN is susceptible to biotic and abiotic transformations, in many environmental instances, transformation mechanisms are difficult to resolve, distinguish, or apportion on the basis solely of analysis of concentrations. We used compound-specific isotope analysis (CSIA) to investigate the characteristic isotope fractionations of the biotic (by three microbial consortia and three pure cultures) and abiotic (by 9,10-anthrahydroquinone-2-sulfonic acid [AHQS]) transformations of DNAN. The correlations of isotope enrichment factors (ΛN/C) for biotic transformations had a range of values from 4.93 ± 0.53 to 12.19 ± 1.23, which is entirely distinct from ΛN/C values reported previously for alkaline hydrolysis, enzymatic hydrolysis, reduction by Fe2+-bearing minerals and iron-oxide-bound Fe2+, and UV-driven phototransformations. The ΛN/C value associated with the abiotic reduction by AHQS was 38.76 ± 2.23, within the range of previously reported values for DNAN reduction by Fe2+-bearing minerals and iron-oxide-bound Fe2+, albeit the mean ΛN/C was lower. These results enhance the database of isotope effects accompanying DNAN transformations under environmentally relevant conditions, allowing better evaluation of the extents of biotic and abiotic transformations of DNAN that occur in soils, groundwaters, surface waters, and the marine environment.

We report the draft genome sequences of Pseudomonas extremaustralis NQ5, Arthrobacter strain NQ4, and Arthrobacter strain NQ7 isolated from a laboratory-scale membrane bioreactor, soils from San Antonio, TX, USA and sediments from Galveston Bay, TX, USA, respectively. These bacteria degrade the explosive compound nitroguanidine, which is present in some insensitive munitions.

New energetic formulations containing insensitive high explosives (IHE), such as 2,4-dinitroanisole (DNAN), 3-nitro-1,2,4-triazole-5-one (NTO), and nitroguanidine (NQ) are being developed to provide safer munitions. The addition of IHE to munitions formulations results in complex wastewaters from explosives manufacturing, load and pour operations and demilitarization activities. New technologies are required to treat those wastewaters. The core objective of this research effort was to develop and optimize a dual anaerobic-aerobic membrane bioreactor (MBR) system for treatment of wastewater containing variable mixtures of traditional energetics, IHE, and anions. The combined system proved highly effective for treatment of traditional explosives (TNT, RDX, HMX), IHE (DNAN, NTO, NQ) and anions commonly used as military oxidants (ClO4−, NO3−). The anaerobic MBR, which was operated for more than 500 d, was observed to completely degrade mg L−1 concentrations of TNT, DNAN, ClO4− and NO3− under all operational conditions, including at the lowest hydraulic residence time (HRT) tested (2.2 d). The combined system generally resulted in complete treatment of mg L−1 concentrations of RDX and HMX to <20 μg L−1, with most of the degradation occurring in the anaerobic MBR and polishing in the aerobic system. No common daughter products of DNAN, TNT, RDX, or HMX were detected in the effluent. NTO was completely transformed in the anaerobic MBR, but residual 3-amino-1,2,4-triazole-5-one (ATO) was detected in system effluent. The ATO rapidly decomposed when bleach solution was added to the final effluent. NQ was initially recalcitrant in the system, but microbial populations eventually developed that could degrade >90% of the ∼10 mg L−1 NQ entering the anaerobic MBR, with the remainder degraded to <50 μg L−1 in the aerobic system. The dual MBR system proved to be capable of complete degradation of a wide mixture of munitions constituents and was resilient to changing influent composition.

Nitroguanidine (NQ) is a component of newly developed insensitive munition (IM) formulations which are more resistant to impact, friction, heat, or sparks than conventional explosives. NQ is also used to synthesize various organic compounds and herbicides, and has both human and environmental health impacts. Despite the wide application and associated health concerns, limited information is known regarding NQ biodegradation, and only one NQ-degrading pure culture identified as Variovorax strain VC1 has been characterized. Here, we present results for three new NQ-degrading bacterial strains isolated from soil, sediment, and a lab-scale aerobic membrane bioreactor (MBR), respectively. Each of these strains -utilizes NQ as a nitrogen (N) source rather than as a source of carbon or energy. The MBR strain, identified as Pseudomonas extremaustralis strain NQ5, is capable of degrading NQ at a rate of approximately 150 μmole L-1 h-1 under aerobic conditions with glucose as a sole carbon source - and NQ as a sole N source. The addition of NH4+ to strain NQ5 during active growth with NQ as a sole N source slowed the growth rate for several hours, and the strain released NH4+, presumably from NQ. When NO3- was added as an alternate N source under similar conditions, the NO3- was not consumed, but NH4+ release into the culture medium was again observed. Strain NQ5 was also able to utilize guanylurea, guanidine, and ethyl allophanate as N sources, and - tolerate salt concentrations as high as 4 % (as NaCl). The other two stains, NQ4 and NQ7, both identified as Arthrobacter spp., grew significantly slower than strain NQ5 under similar culture conditions and tolerated only ∼1 % NaCl. In addition, neither strain NQ4 nor strain NQ7 was able to degrade guanlyurea or ethyl allophanate, but each degraded guanidine. These strains, particularly strain NQ5, may have practical applications for in-situ and ex-situ NQ bioremediation.

Technologies are needed to address contamination with energetic compounds at military installations. This research developed and evaluated novel and sustainable materials that can be used to remove munition constituents (MC) from stormwater runoff. Initial work focused on 3-nitro-1,2,4-triazol-5-one (NTO), as it is both highly soluble and ionized at environmentally relevant pH values. Screening cellulosic materials indicated that cationized (CAT) versions of pine shavings (pine, henceforth) and burlap (jute) demonstrated >70% removal of NTO from artificial surface runoff. CAT materials also demonstrated >90% removal of the anionic propellant perchlorate. NTO removal (~80%) by CAT pine was similar across initial pH values from 4 to 8.5 S.U. An inverse relationship was observed between NTO removal and the concentration of the major anions chloride, nitrate, and sulfate due to competition for anion binding sites. Sorption isotherms were performed using a mixture of the three primary legacy explosives (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), hexahydro-1,3,5-trinitro-s-triazine (RDX), 2,4,6-trinitrotoluene (TNT)), the three insensitive MC (nitroguanidine (NQ), NTO, 2,4-dinitroanisole (DNAN)), and perchlorate. Isotherm results indicated that effective removal of both legacy and insensitive MC would best be achieved using a mixture of peat moss plus one or more of the cationized cellulosic materials.

The high potential of oxymethylene ethers (OMEs) and related compounds as fuels and fuel-additives motivated a multitude of experimental and theoretical investigations on, e.g., dimethoxy methane (DMM), the smallest member of the OME family. The present work adds to this research by providing combined experimental and theoretical rate coefficients for di- and trimethoxy methane (TMM) pyrolysis. For DMM pyrolysis, the branching ratios between the major dissociation pathways remained elusive in recent studies and is elucidated in the present work using four independent sets of shock tube experiments and master equation modeling. For TMM pyrolysis, the present work provides the very first detailed chemical kinetics model. A key consumption reaction of both compounds, DMM and TMM, is the methoxy-induced H-atom migration, which yields methanol and a singlet diradical. While for DMM this reaction is in direct competition to the C-O bond fission reactions, TMM is found to be a prime example for methoxyinduced H-atom migration, as its pyrolysis chemistry is exclusively governed by this reaction. With the present work, the details of DMM pyrolysis are elucidated and the foundation is laid for detailed chemical kinetics modeling of TMM. (c) 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Laminar flame speed and ignition delay time measurements are presented for blends of isopropyl-nitrate and propane. The laminar flame speeds were measured in a spherical bomb, with the majority of the experiments performed at 373 K and 1 bar, with equivalence ratios between 0.6 <ϕ< 2.1; the fuel composition was 0%, 10%, and 100% isopropyl-nitrate. Additional experiments were performed at 300 K for pure propane as a fuel, and at 0.5 bar for pure isopropyl-nitrate as fuel. The ignition delay measurements were performed in a shock tube, with reflected shock temperatures between 1050 K and 1530 K and a nominal reflected shock pressure of 20 bar. Equivalence ratios of 0.5, 1.0, and 1.5 were considered for fuel blends with 0% and 1% isopropyl-nitrate in propane; additional experiments were performed with 10% isopropyl-nitrate at ϕ = 1. In comparison with the pure propane flames, the pure isopropyl-nitrate have a similar peak flame speed (SL0=60.3 cm/s at ϕ=1.09 for isopropyl-nitrate versus SL0=57.9 cm/s at ϕ=1.10 for propane), but the nitrate is considerably faster under fuel lean conditions, and it exhibits a much broader domain. The ignition delay times for 1% isopropyl-nitrate in propane are indistinguishable from the pure propane experiments for all three equivalence ratios. The 10% isopropyl-nitrate in propane mixture, in contrast, is significantly more reactive. Transition state theory calculations were performed for select RH + NO2 reactions. These calculations were added to a recently developed mechanism for isopropyl-nitrate and propane. Detailed simulations of the experiments were performed in Cantera. The agreement between the models and experiments is excellent. The largest discrepancies occur for the ignition delay times for 10% isopropyl-nitrate at T5<1150 K and for the flame speeds for ϕ>1.8, which suggests that further work needs to be done under these conditions. To the best of our knowledge, these data represent the first published results on the laminar flame speeds of any alkyl nitrate.

The environmental fate of 3-nitro-1,2,4-triazol-5-one (NTO) and other insensitive munitions constituents (MCs) is of significant concern due to their high water solubility and mobility relative to legacy MCs. Plant-based biochars have been shown to possess a considerable electron storage capacity (ESC), which enables them to undergo reversible electron transfer reactions. We hypothesized biochar can act as a rechargeable electron donor to effect abiotic reduction of MCs repeatedly through its ESC. To test this hypothesis, MC reduction experiments were performed using wood-derived biochars that were oxidized with dissolved oxygen or reduced with dithionite. Removal of aqueous NTO, an anion at circumneutral pH, by oxidized biochar was minimal and occurred through reversible adsorption. In contrast, NTO removal by reduced biochar was much more pronounced and occurred predominantly through reduction, with concomitant formation of 3-amino-1,2,4-triazol-5-one (ATO). Mass balance and electron recovery with ferricyanide further showed that (1) the amount of NTO reduced to ATO was relatively constant (85-100 μmol per gram of biochar) at pH 6-10; (2) the fraction of biochar ESC reactive toward NTO was ca. 30% of that toward ferricyanide; (3) the NTO-reactive fraction of the ESC was regenerable over multiple redox cycles. We also evaluated biochar transformation of other MCs, including nitroguanidine (NQ), 2,4-dinitroanisole (DNAN), and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). While mass and electron balances could not be established due to sorption, DNAN and RDX reduction by reduced biochar was confirmed via detection of multiple reduction products. In contrast, NQ was not reduced under any of the conditions tested. This study is the first demonstration of organic contaminant degradation through biochar's rechargeable ESC. Our results indicate biochar is a regenerable electron storage medium and sorbent that can remove MCs from water through concurrent reduction and sorption, and is thus potentially useful for pollution control and remediation at military facilities.