Neal Adrian

Alachlor is a pre-emergence chloroacylanilide herbicide in widespread use, marketed as Lasso. In South Dakota, chemical spills amounting to nearly 9,000 gallons of pesticides and their solvents have been reported for the past two growing seasons. A large portion of this material has been alachlor; since many spills are not reported, its presence in the environment in high levels may be substantially greater than this.

Biodegradation of the energetic compound 2,4,6-trinitrotoluene (TNT) and its intermediate 2,4,6-triaminotoluene (TAT) was investigated in this study. From previous investigations, a relationship between the biological utilization of ethanol as co-substrate for the reduction of TNT under anaerobic conditions was proposed using an anaerobic fluidized-bed reactor (AFBR). In this study, the theoretical co-substrate requirement for reduction of TNT to TAT was further investigated through the systematic lowering of the ethanol loading to the reactor. Near complete reduction to TAT was observed up to a critical ethanol loading point, as well as the production of methane from the limited excess available ethanol. Once ethanol deficient loading conditions were established, the increased presence of incompletely reduced degradation intermediates, such as 2,4-diamino-6-nitrotoluene, and even TNT, was observed. The cessation of methanogenesis confirmed that no excess ethanol was available. Degradation of the TAT intermediate in the reactor effluent was investigated using two second-stage reactors under oxidizing conditions. The first was an aerobic activated sludge reactor, and the second was a denitrifying fluidized-bed reactor (DenFBR). The aerobic reactor was successful in lowering the chemical oxygen demand (COD), but complete removal of TAT was not accomplished. Because of TAT polymerization and auto-oxidation under aerobic conditions, it was difficult to confirm to what extent of TAT removal was biological. In the DenFBR, incompletely reduced TNT intermediates were not successfully degraded, but strong evidence existed for the degradation of TAT. This is the first known report of second stage degradation of TAT under denitrifying conditions.

Abstract : Pinkwater, a hazardous wastewater containing 2,4,6-trinitrotoluene (TNT), is produced during munition production or demilitarization operations. Anaerobic bioreactors are under investigation as an alternative to activated carbon for treating pinkwater. This research studied the microbial community structure of an anaerobic bioreactor treating a synthetic feed containing ethanol and TNT. Samples from the reactor were taken weekly, ribonucleic acid (RNA) was extracted and membrane hybridizations were performed using ologonucleotide probes specific for the domains Bacteria and Archaea. The bacterial and archaeal ribosomal RNA (rRNA) were similar between the two reactors, but, after doubling the TNT loading, the archaeal rRNA decreased and the bacterial rRNA increased. In response to the increased TNT loading, the alpha-Proteobacteria increased to 60 percent of the bacterial rRNA, but remained unchanged in the control reactor. In the control reactor, the Methanosarcinales accounted for about 80 percent of the archaeal rRNA, while, in the +TNT reactor, they decreased from about 50 percent to 20 percent after increasing the TNT loading. The Methanomicrobiales accounted for about 80 percent of the Archaea, while they were barely detectable in the control reactor. The findings indicate that TNT significantly affects the bacterial and archaeal community structure. Several strategies are suggested for assessing and optimizing anaerobic bioreactors treating pinkwater.

A streptomycete bacterium was isolated from a field soil sample previously treated with the insecticide isofenphos and found to be capable of growing on several commercial carbamate and organophosphate insecticides. These included carbofuran, cloethocarb, ...

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.

This study examined the biodegradation of RDX in wastewater from an industrial wastewater treatment plant at the Holston Army Ammunition Plant in Kingsport, TN. Serum bottles containing 100 ml of a basal salts medium amended with 10 percent (v/v) sludge from the anoxic filter at the plant were amended with RDX and incubated under methanogenic conditions. Biodegradation intermediates corresponding to

We studied the metabolic fate of bromacil in anaerobic aquifer slurries held under denitrifying, sulfate-reducing, or methanogenic conditions. Liquid chromatograhy-mass spectrometry of the slurries confirmed that bromacil was debrominated under methanogenic conditions but was not degraded under the other incubation conditions. This finding extends the range of aryl reductive dehalogenation reactions to include nitrogen heterocyclic compounds.

Accurate predictions of carbon and energy cycling rates in the environment depend on sampling frequencies and on the spatial variability associated with biological activities. We examined the variability associated with anaerobic biodegradation rates at two sites in an alluvial sand aquifer polluted by municipal landfill leachate. In situ rates of methane production were measured for almost a year, using anaerobic wells installed at two sites. Methane production ranged from 0 to 560 mumol . m . day at one site (A), while a range of 0 to 120,000 mumol . m . day was measured at site B. The mean and standard deviations associated with methane production at site A were 17 and 57 mumol . m . day, respectively. The comparable summary statistics for site B were 2,000 and 9,900 mumol . m . day. The coefficients of variation at sites A and B were 340 and 490%, respectively. Despite these differences, the two sites had similar seasonal trends, with the maximal rate of methane production occur...

Abstract: The US Army generates large volumes of explosives-contaminated wastewater during munitions production and demilitarization operations. Contaminants such as 2, 4, 6-trinitrotoluene (TNT) and hexahydro-l, 3, 5-trinitro-l, 3, 5-triazine (RDX) are ...

We studied the anaerobic biodegradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in a mineral medium by a mixed culture. RDX degradation activity was maintained for more than a year with only the addition of RDX. We observed a steady increase in the protein concentration of the culture from 4.8 microg mL(-1) to more than 24.4 microg mL(-1), a >400% increase. There was only a slight increase in protein in the RDX unamended control bottles containing live culture, increasing from 4.8 microg mL(-1) to 7.8 microg mL(-1). Radiolabeled (14)C-RDX confirmed mineralization of the cyclic nitramine to (14)CO(2). After 164 days, 35% of the radiolabel was recovered as 14CO2. This is the first report demonstrating the mineralization of RDX when it serves as a growth substrate for a mixed culture.

Past handling practices associated with the manufacturing and processing of the high explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has resulted in extensive environmental contamination. In-situ biodegradation is a promising technology for remediating RDX contaminated sites but often relies on the addition of a cosubstrate. A sulfate-reducing bacterium isolated from an RDX-degrading enrichment culture was studied for its ability to grow on RDX as a sole source of carbon and nitrogen and for its ability to mineralize RDX in the absence of a cosubstrate. The results showed the isolate degraded 140 muM RDX in 63 days when grown on RDX as a carbon source. Biomass within the carbon limited culture increased 9-fold compared to the RDX unamended controls. When the isolate was incubated with RDX as sole source of nitrogen it degraded 160 muM RDX in 41 days and exhibited a 4-fold increase in biomass compared to RDX unamended controls. Radiolabeled studies under carbon limiting conditions with (14)C-hexahydro-1,3,5-trinitro-1,3,5-triazine confirmed mineralization of the cyclic nitramine. After 60 days incubation 26% of the radiolabel was recovered as (14)CO(2), while in the control bottles less than 1% of the radiolabel was recovered as (14)CO(2). Additionally, approximately 2% of the radiolabeled carbon was found to be associated with the biomass. The 16S rDNA gene was sequenced and identified the isolate as a novel species of Desulfovibrio, having a 95.1% sequence similarity to Desulfovibrio desulfuricans. This is the first known anaerobic bacterium capable of mineralizing RDX when using it as a carbon and energy source for growth.