Bioremediation of 2,4,6-Trinitrotoluene under Field Conditions (original) (raw)
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Periodica Polytechnica Chemical Engineering, 2016
This review paper provides a critical examination on current microbial biodegradation of 2, 4, 6-Trinitrotoluene (TNT) and its metabolites in soil, with focus on: (i) extent of biological degradation of TNT and its metabolites in soil, (ii) factors affecting the TNT transformations, and (iii) microbial bioremediation technologies , and related challenges. This was carried out through an extensive examination of relevant published literature on the topic. The review paper found that the detoxification of TNT contaminated sites by microorganisms based-technologies have been employed but TNT has been proven to resist biological mineralization and undergo biotransformations, leading to immobilization of toxic and unstable transformation products. TNT mineralization is however achievable, but scientific studies are far away from attaining the best desired in situ bioremediation practices and much remains to be delineated. We provide future research directions to design effective bioremediation technologies for solving the problems of TNT and minimize environmental impacts.
Bioremediation of TNT contaminated soil with fungi under laboratory and pilot scale conditions
International Biodeterioration & Biodegradation, 2015
Bioremediation of contaminated soil involves the utilization of innovative technology such as mycoremediation. The capability of fungi to grow in 2,4,6-trinitrotoluene (TNT) contaminated soil, to produce lignin modifying enzymes and to degrade TNT in soil was studied. White-rot fungi, namely Gymnopilus luteofolius, Kuehneromyces mutabilis, and Phanerochaete velutina, were incubated with TNT contaminated non-sterile soil (1000 mg kg À1). All the fungi produced high amounts of manganese peroxidase (MnP) in TNT contaminated soil, but no laccase. The most efficient fungus, P. velutina, degraded 80% of TNT in 2.5 months and was selected for further scale-up experiment with 0.3 t (0.56 m 3) of soil and inoculum soil ratio of 1:30. The degradation of TNT was 70% in 49 days, and production of fungal metabolites, namely 4-amino-2,6-diaminotoluene and 2-amino-4,6-diaminotoluene was only 1% of the original TNT concentration. These metabolites were degraded to less than 0.5% during the following 58 days incubation. Fungal remediation process was scaled-up with P. velutina, which tolerated high concentration of TNT and was able to invade the whole mass of soil with only 10 kg of fungal inoculum growing on pine bark. With these parameters the process should be easy to scale-up for soil treatment in field.
Degradation of 2,4,6-Trinitrotoluene (TNT)by Soil Bacteria Isolated From TNT Contaminated Soil
Twenty bacterial strains isolated from TNT contaminated soil. Among those strains only five were highly efficient for their abilities to grow in basal salt medium containing TNT as sole nitrogen source. From these isolates only two strains were more potent for TNT degradation in aerobic condition. These strains were identified as Clavibacter agropyi (Corynebacterium) (R.L1) and Sphingomonas sanguinis (R.L2).These strains had shown good growth with disappearance of TNT and concomitantly release of nitrite over the period of incubation time. TNT and its metabolites were analyzed by gas chromatography (GC) and results were confirmed and identified by gas chromatography/Mass spectrometer (GC/MS). The biodegradation of TNT was initially similar regardless of the microorganism. Generally, the initial degradation involved the reduction or removal of the nitro substitute giving way to an amino derivative or free nitrite. The identified amino derivatives were, P-toluidine,3,5-dinitro and Benzenamine,2-methyl-3,5-dinitro.which are known as 2amino-4,6-dinitrotoluene(2-ADNT) and 4-amino-2,6-dinitrotoluene (4-ADNT) respectively. Nitrite liberation was consistently found coincided with TNT disappearance from the medium. The disappearance of TNT was completely within 7days by the two isolates and/or their mixture. This is encouraging, and may indicate their potential in bioremediation of TNT contaminated soils. This is the first report on Clavibacterium agropyri (Corynebacterium) and Sphingomonas sanguinis for degradation of TNT with nitrite release into the medium.
Journal of Environmental Management, 2012
Environmental contamination by TNT (2,4,6 trinitrotoluene), historically used in civilian industries and the military as an explosive is of great concern due to its toxicity. Scientific studies have however shown that TNT is susceptible to microbial transformation. The aim of this study was to assess the potential of a previously bioremediated hydrocarbon contaminated soil (PBR) to increase TNT degradation rates. This was investigated by adding TNT chips to PBR and uncontaminated soils (PNC) in laboratory based studies (up to 16 weeks). Residual TNT chip analysis showed greater TNT degradation in PBR soils (70%) and significantly higher metabolic rates (4.5 fold increase in cumulative CO 2 levels) than in PNC soils (30%). Molecular analysis (PCR-DGGE-cluster analysis) showed substantial shifts in soil microbial communities associated with TNT contamination between day 0 and week 4 especially in PBR soils. Bacterial communities appeared to be more sensitive to TNT contamination than fungal communities in both soils. Quantitative PCR analysis showed w3 fold increase in the abundance of nitroreductase genes (pnrA) in PBR soils with a gradual reduction in community evenness (Pareto-Lorenz curves) in contrast to PNC soils. These results suggest that microbial response to TNT contamination was dependent on the history of soil use. The results also confirm that the microbial potential of waste soils such as PBR soil (usually disposed of via landfill) can be successfully used for accelerated TNT chip degradation. This promotes sustainable re-use of waste soils extending the life span of landfill sites.
Archives of Environmental Contamination and Toxicology, 1997
In earlier studies , soil bacteria present in a TNT-contaminated site removed 2,4,6trinitrotoluene (TNT). In this study the optimum conditions for the most efficient removal of TNT is discussed. The results suggest that the soil bacterial consortium has an optimal pH range of 6-7. Maximum growth was observed at pH 7. However, the TNT removal rate was higher at pH 6. Studies of the effects of temperature showed that the bacterial consortium had maximum metabolic activity at 20 to 22°C (ambient temperature). At a higher temperature (37°C) the TNT removal rate dropped significantly. The consortium could not use TNT as a nitrogen source but required the addition of ammonium. Optimal growth occurred with 0.25 g/L of ammonium chloride. Growing cells removed TNT significantly faster rates than resting cells or cell-free extract. The operation of soil slurry reactors with the optimal conditions suggested that TNT can be removed effectively from the contaminated sites. These environmental conditions established as optimal can be used to improve the efficiency of large-scale soil slurry reactors for the treatment of soil contaminated with TNT.
2022
2,4,6-Trinitrotoluene (TNT), a nitro-aromatic explosive commonly used for defence and several non-violent applications is contributing to serious environmental pollution problems including human health. The current study investigated the remediation potential of a native soil isolate i.e., Planomicrobium flavidum (strain S5-TSA-19) against TNT. At a TNT concentration of 120 mg/L with a specified environment, the isolate remained incubated for 30 days in a minimal salt medium (MSM). Regular growth of the isolate, the concentration of TNT, nitrate, nitrite and ammonium ion were evaluated at a particular time during the experiment. Within 168 hours (i.e., 7 days) of incubation, P. flavidum co-metabolically degraded 100% TNT. The biodegradation procedure succeeded the first order kinetics mechanism. Formation of additional metabolites like 2,4-dinitrotoluene (DNT), 2,4-diamino-6-nitrotoluene (2-DANT) and 2-amino-4,6-dinitrotoluene (2-ADNT), were also witnessed. TNT seems to be non-toxic...
Bioresource Technology, 1994
Four Pseudomonas spp. were isolated from a soil consortium enriched from soil contaminated with 2,4,6-trinitrotoluene (TNT). All four species extensively transformed TNT. The rate of transformation varied among species. In isolate 4, 100% of TNT (100 ppm) was transformed in 4 days. The TNT transformation was achieved by the four isolates through a co-metabolic process with a succinate co-substrate. The four isolates produced NOj from TNT. The maximum NO;-production, observed for isolate 1, was equal to 30% of the NO; available from the nitro groups of TNT. For other isolates the NO;_ production varied from 10 to 16%. The radiolabeling studies showed signs of ring cleavage. Isolate 3 used 13%
2013
In this environmental-sample based study, rapid microbial-mediated degradation of 2,4,6-trinitrotoluene (TNT) contaminated soils is demonstrated by a novel strain, Achromobacter spanius STE 11. Complete removal of 100 mg L À1 TNT is achieved within only 20 h under aerobic conditions by the isolate. In this bio-conversion process, TNT is transformed to 2,4-dinitrotoluene (7 mg L À1 ), 2,6-dinitrotoluene (3 mg L À1 ), 4-aminodinitrotoluene (49 mg L À1 ) and 2-aminodinitrotoluene (16 mg L À1 ) as the key metabolites. A. spanius STE 11 has the ability to denitrate TNT in aerobic conditions as suggested by the dinitrotoluene and NO 3 productions during the growth period. Elemental analysis results indicate that 24.77 mg L À1 nitrogen from TNT was accumulated in the cell biomass, showing that STE 11 can use TNT as its sole nitrogen source. TNT degradation was observed between pH 4.0e8.0 and 4e43 C; however, the most efficient degradation was at pH 6.0e7.0 and 30 C.
Bioremediation of 2,4,6-Trinitrotoluene Contaminated Soil in Slurry and Column Reactors
Journal of Bioscience and Bioengineering, 2003
Two composting systems were compared on a laboratory scale as a bioremediation technology for degradation or immobilization of 2,4,6-trinitrotoluene (TNT) in contaminated soils. The first compost was aerated from the beginning whereas the second compost was only aerated after an anaerobic prephase of 65 days. In the first compost system the TNT concentration declined rapidly by 92% but, at the end, TNT could be partially recovered. During the anaerobic prephase of the second compost system, TNT was almost completely converted to aminodinitrotoluenes, which during the subsequent aeration almost entirely disappeared. In addition, the second compost generated less toxic material than the first one as confirmed by inhibition of bioluminescence of Vibrio fischeri.