Analysis of new generation explosives in the presence of u.s. EPA method 8330 energetic compounds by high-performance liquid chromatography.

U.S. EPA Method 8330 was evaluated and modified for the analysis of DNAN (2,4-dinitroanisole) and MNA (n-methyl-p-nitroaniline) by high-performance liquid chromatography in various aqueous media in the presence and absence of the 14 energetic compounds currently assigned to the method. DNAN and MNA are two of the four components in PAX-21, a new generation explosive formulation. An optimized method was developed to separate all 14 energetic compounds from DNAN and MNA using a tertiary mobile phase of water-methanol-acetonitrile (68:28:4) in an isocratic run of 35 min. The limit of detection (LOD, 3S(0)) was calculated to be 10 ppb for both MNA and DNAN. The limit of quantitation (LOQ, 10S(0)) was 40 ppb for both compounds. The dynamic ranges for the two compounds were very wide, a nearly 5 orders of magnitude range from 0.02 to 1,000 parts per million (ppm). The spike recoveries of MNA and DNAN in environmental matrix samples were excellent for DNAN, from 87% to 113%. For MNA, the recoveries were slightly high at the low level (60 ppb), probably due to some contamination in the ditch and pond matrices; but they were satisfactory at higher levels ranging from 85% to 121%.

Anaerobic treatment of army ammunition production wastewater containing perchlorate and RDX.

Perchlorate is an oxidizer that has been routinely used in solid rocket motors by the Department of Defense and National Aeronautics and Space Administration. Royal Demolition Explosive (RDX) is a major component of military high explosives and is used in a wide variety of munitions. Perchlorate bearing wastewater typically results from production of solid rocket motors, while RDX is transferred to Army industrial wastewaters during load, assemble and pack operations for new munitions, and hot water or steam washout for disposal and deactivation of old munitions (commonly referred to as demilitarization, or simply demil). Biological degradation in Anaerobic Fluidized Bed Reactors (AFBR), has been shown to be an effective method for the removal of both perchlorate and RDX in contaminated wastewater. The focus of this study was to determine the effectiveness of removal of perchlorate and RDX, individually and when co-mingled, using ethanol as an electron donor under steady state conditions. Three AFBRs were used to assess the effectiveness of this process in treating the wastewater. The performance of the bioreactors was monitored relative to perchlorate, RDX, and chemical oxygen demand removal effectiveness. The experimental results demonstrated that the biodegradation of perchlorate and RDX was more effective in bioreactors receiving the single contaminant than in the bioreactor where both contaminants were fed.

Physicochemical properties of an insensitive munitions compound, N-methyl-4-nitroaniline (MNA).

Accurate information on physicochemical properties of an organic contaminant is essential for predicting its environmental impact and fate. These properties also provide invaluable information for the overall understanding of environmental distribution, biotransformation, and potential treatment processes. In this study the aqueous solubility (Sw), octanol-water partition coefficient (Kow), and Henry's law constant (K(H)) were determined for an insensitive munitions (IM) compound, N-methyl-4-nitroaniline (MNA), at 298.15, 308.15, and 318.15 K. Effect of ionic strength on solubility, using electrolytes such as NaCl and CaCl2, was also studied. The data on the physicochemical parameters were correlated using the standard Van't Hoff equation. All three properties exhibited a linear relationship with reciprocal temperature. The enthalpy and entropy of phase transfer were derived from the experimental data.

Pertubated loading of a formaldehyde waste in an anaerobic granular activated carbon fluidized bed reactor.

The objective of this study was to examine the biological treatment of a formaldehyde waste simulating wastewater from a resin production facility. An analysis of degradation of a high strength organic waste stream containing formaldehyde in an anaerobic fluidized bed granular activated carbon bioreactor (AFBGAC) is presented. In the first part of this study, the AFBGAC bioreactor was operated for a total of 700 days under four different continuous loading rates, to optimize the hydraulic retention time, until steady state performance was obtained. In the second part, the effect of substrate perturbation on effluent quality was examined by periodically loading the reactor using five distinct perturbation schemes to simulate different production shifts. The feed under the first three perturbation schemes was applied in cycles of 16 h on and 8 h off, 12 h on and 12 h off, and 8 h on and 16 h off. The fourth scheme applied feed at 8 h on and 16 h off with no feed on weekends. The fifth scheme examined the long-term effect of substrate limitation using the 8 h on and 16 h off loading cycle with a feed interruption of 9 days. The organic loading per day was kept constant throughout the feed perturbation study. The reactor removed more than 95% of the dissolved organic carbon content of the waste under both continuous and cyclic loading. Formaldehyde removal rates of up to 99.99% were achieved under continuous loading while removal rates ranged from 97.4% to 99.9% under cyclic loading. Although the AFBGAC failed occasionally due to excessive buildup of attached biomass during the phase of continuous loading, it still maintained excellent overall removal efficiencies. It also showed resilience to substrate limitations and load perturbations under dynamic loadings. The results presented in this study provide a promising strategy to treat inhibitory wastes.

Anaerobic treatment of pinkwater in a fluidized bed reactor containing GAC.

Pinkwater is generated during the handling and demilitarization of conventional explosives. This listed hazardous waste contains dissolved trinitrotoluene (TNT) and cyclo trimethylene trinitramine (RDX), as well as some by-products. It represents the largest quantity of hazardous waste generated by the operations support command, and its treatment produces a by-product hazardous waste--spent granular activated carbon (GAC). Anaerobic treatment in a fluidized bed reactor (FBR) containing GAC is an emerging technology for organic compounds resistant to aerobic biological treatment. Bench scale batch studies using an anaerobic consortium of bacteria fed ethanol as the sole electron donor demonstrated the transformation of TNT to triaminotoluene (TAT), which then degrades to undetectable end products. RDX is sequentially degraded to nitroso-, dinitroso-, trinitroso- and hydroxylaminodinitroso-RDX before the triazine ring is presumably cleaved, forming methanol and formaldehyde as major end products. The bacterial members of the anaerobic consortia are typically found in sludge digesters at municipal or industrial wastewater treatment plants. The results of a pilot scale evaluation of this process that was conducted at McAlester Army Ammunition Plant (MCAAP, OK) over a 1 year period are reported in this paper. The pilot test experienced wide fluctuations in influent concentrations, representative of true field conditions. The FBR was a 20 in. (51 cm) diameter column with an overall height of 15 ft (4.9 m) and a bed of GAC occupying 11 ft (3.4m). Water was recirculated through the column continuously at 30 gpm (114 l/min) to keep the GAC fluidized, and pinkwater for treatment was pumped into the recirculation line. Several flowrates were evaluated to determine the proper mass loading rate (mass of TNT and RDX per reactor volume per time, kg/m(3) per day) which the reactor could handle while meeting the discharge limitations. Based on the tests performed, a 1 gpm (3.785 l/min) rate in the 188 gal (710 l) volume of the fluidized GAC bed was determined to consistently meet the discharge requirements. This information was used to develop a cost estimate for a system capable of treating the total effluent currently produced at MCAAP. The cost of installing and operating this system was compared to the cost of GAC adsorption for MCAAP at current pinkwater generation rates. The GAC-FBR system had an annual operating cost of approximately US$ 19K, compared to US$ 71 K annually for GAC adsorption. When including the amortization of the capital equipment required for the GAC-FBR, the payback period for installation of this new process was estimated at 3.7 years.

Biological transformation pathways of 2,4-dinitro anisole and N-methyl paranitro aniline in anaerobic fluidized-bed bioreactors.

The US Army is evaluating new, insensitive explosives to produce safer munitions. Two potential new components are 2,4-dinitro anisole (DNAN) and N-methyl paranitro aniline (MNA), which would eventually make their way to waste streams generated in the production and handling of new munitions. The effectiveness of anaerobic fluidized-bed bioreactors (AFBB) was studied for treatment and transformation of these two new chemical components in munitions. Each compound was fed into a separate reactor and monitored for removal and transformation, using ethanol as the electron donor. The results show that both were degradable using the AFBB system. DNAN was found to transform into diaminoanisole and MNA was found to transform into N-methyl-p-phenylenediamine. Both of these by-products appeared to form azobond polymers after exposure to air. To test the resilience of the reactors, the compounds were removed from the feed streams for 3 weeks and then reintroduced. DNAN showed that a re-acclimation period was necessary for it to be degraded again, while MNA was removed immediately upon reintroduction. The AFBB technology was shown here to be an effective means of removing the new munitions, but produce secondary compounds that could potentially be just as harmful and require further study.

Analysis of bacterial community diversity in anaerobic fluidized bed bioreactors treating 2,4-dinitroanisole (DNAN) and n-methyl-4-nitroaniline (MNA) using 16S rRNA gene clone libraries.

Clone libraries were used to evaluate the effects of 2,4-dinitroanisole (DNAN) and n-methyl-4-nitroaniline (MNA) on bacterial populations within three anaerobic bioreactors. Prior to the addition of DNAN and MNA greater than 69% of the clones in each reactor were identified as a single Desulfuromonales species. However, after 60 days of treatment the Desulfuromonales distribution decreased to less than 13% of the distribution and a clone identified as a Levilinea sp. became the dominant organism at greater than 27% of the clone distribution in each reactor suggesting the species may play an important roll in the reduction of DNAN and MNA.