Stephen W. Maloney

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

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

19K, compared to US

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

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.

ANAEROBIC TREATMENT OF ARMY AMMUNITION PRODUCTION WASTEWATER CONTAINING PERCHLORATE AND RDX

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.

Electrochemical Reduction of Simulated Munitions Wastewater in a Bench-Scale Batch 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.

Factors affecting wet air oxidation of TNT red water: Rate studies

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.

Electrochemical reduction of 2,4,6-trinitrotoluene

2,4,6-Trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) are major constituents of munitions production wastewater discharged from explosive manufacturing units and munitions load, assembly, and pack operations. Experiments were carried out to study the electrochemical reduction of DNT and a mixture of TNT and RDX. The effect of various parameters including current, stir rate, and presence and absence of dissolved oxygen was investigated. Experiments were conducted using glassy carbon rods as the cathode and platinum wire as the anode. End products were also analyzed for the experiments to obtain molar balance closure for the conversion of the nitroaromatic to intermediates. The experimental results showed that the electrochemical reduction of nitroaromatics follow pseudo first-order rate kinetics. The first-order rate constants for the reduction of nitroaromatics were observed to increase with an increase in current or stir rate. The rate of reduction of th...

Treatment of Energetic Wastewater Containing 2,4-Dinitroanisole and N-Methyl Paranitro Aniline

Abstract Preliminary experiments have demonstrated wet air oxidation (WAO) to be feasible for TNT red water treatment. This paper presents the results of rate s

Treatment of 2,4-dinitrotoluene using a two-stage system : fluidized-bed anaerobic granular activated carbon reactors and aerobic activated sludge reactors

A laboratory-scale reactor was used to study the electrochemical reduction of 2,4,6-trinitrotoluene (TNT). A graphite cylinder impregnated with glassy carbon (zero porosity) was used as the cathode...

Biotransformation of 2,4-dinitrotoluene under different electron acceptor conditions

AbstractThe U.S. Army is seeking to produce safer, less sensitive munitions through the addition of two new energetics, 2,4-dinitroanisole (DNAN) and N-methyl paranitro aniline (MNA), to the munitions’ formula. Production of these munitions would add them to the waste stream. The use of an anaerobic fluidized-bed bioreactor (AFBB) was studied for treating these compounds in a simulated wastewater with ethanol as the electron donor. The reactor degraded both of the compounds to below detection limits over a wide range of ethanol concentrations. The degradation was found to be a transformation into secondary products for both energetics: diaminoanisole (for DNAN) and N-methyl-p-phenylenediamine (for MNA). Both of these by-products reacted upon exposure to air, forming azobond dimers. Potassium perchlorate was added to the feed stream to test if additional energetics would disrupt the transformation. The AFBB continued transformation and was able to remove the perchlorate after a two week acclimation period....