Bioremediation of 2,4,6-trinitrotoluene-contaminated groundwater using unique bacterial strains: microcosm and mechanism studies

Abstract

Groundwater at many military factory, munition storage and maneuver sites is contaminated by explosives chemicals that were released into the subsurface. The 2,4,6-trinitrotoluene (TNT) is among the most common explosive pollutants. In this study, two TNT-degrading strains, isolated from TNT-contaminated soils and wastewater sludge, were applied for TNT biodegradation. Based on the 16S rDNA sequence analyses, these two bacterial strains were identified as Achromobacter sp. and Klebsiella sp. via biochemical and DNA analyses. Microcosm study was conducted to evaluate the feasibility and efficiency of TNT biodegradation under aerobic conditions. Results indicate that TNT degradation by-products were detected in microcosms (inoculated with Achromobacter sp. and Klebsiella sp.) with cane molasses addition. Klebsiella sp. and Achromobacter sp. used TNT as the nitrogen source and caused completely removal of TNT. Two possible TNT biodegradation routes could be derived: (1) part of the TNT was transformed to nitrotoluene then transformed to nitrobenzene followed by the nitro substitute process, and trinitrobenzene, dinitrobenzene, and nitrobenzene were detected; and (2) TNT was transformed via the nitro substitute mechanism, and dinitrotoluene followed by nitrotoluene isomers were detected. The initial TNT degradation involved the reduction or removal of the nitro substitute to an amino derivative or free nitrite. Results show that the second route was the dominant TNT biodegradation pathway. The produced by-products were also degraded without significant accumulation during the degradation process. These findings would be helpful in designing a practical system inoculated with isolated TNT degradation strains for the treatment of TNT-contained groundwater.

Nitroaromatic compounds – characteristics and methods of biodegradation

“…Mikroorganizmy również wykorzystywały TNT jako źródło azotu i doprowadziły do jego całkowitej degradacji w ciągu 10 dni. W tym przypadku jako źródło węgla wykorzystano melasę (8 g/l) [90].…”

Treatment of Wastewater Containing Aromatic Nitro Compounds Using the A2o-MBBR Method

“…In addition, TNT and its derivatives can persist and accumulate over the long-term in nature and are difficult to biodegrade [1][2][3]. Therefore, biological methods combined with other pre-treatment methods, that are based on common microbiological methods, enzymes methods, or plant methods, have been developed for the treatment of TNTcontaminated wastewater and soil water [1][2][3][4][5][6][7][8][9][10][20][21][22]. Previous studies on TNT biodegradation used microorganisms, such as immobilized white rot fungi (Phanerochaete chrysosporium), for the treatment of TNT wastewater; biological aerated filters (BAF), anaerobic filters (AF), and anaerobic-anoxic-oxic moving bed biological reactors (A2O-MBBR) are commonly applied to wastewater treatment containing TNT in the next stage [1][2][3][4][5] after the wastewater has been pre-treated by physical or chemical methods.…”

Evaluación de la transformación de pentolita solida por bacterias degradadoras de TNT y PETN

“…La presencia del explosivo sólido en altas concentraciones, las condiciones de anaerobiosis, baja temperatura (~ 21 °C), oscuridad en las que se realizó el estudio de los microcosmos tuvieron un gran impacto en el desempeño de las diferentes bacterias, cultivos mixtos y consorcios definidos. El amplio repertorio de bacterias transformadoras de TNT y PETN seleccionadas por Ávila y Garcia (Ávila, 2012;García, 2014) son bacterias que se también se han encontrado en otros estudios de transformación de explosivos como el TNT y el RDX (Erkelens et al, 2012;Kalsi et al, 2020;Sheu et al, 2016). Las bacterias en estos estudios también provienen de sitios contaminados con explosivos.…”