The explosive 2,4,6-trinitrotoluene (TNT), found as a major contaminant at armament plants from the two world wars, is reduced by a variety of microorganisms when electron donors such as glucose are added. This study shows that the cometabolic reduction of TNT to 2,4,6-triaminotoluene by an undefined anaerobic consortium increased considerably with increasing TNT concentrations and decreased with decreasing concentrations and feeding rates of glucose. The interactions of TNT and its reduction products with montmorillonitic clay and humic acids were investigated in abiotic adsorption experiments and during the microbial reduction of TNT. The results indicate that reduction products of TNT particularly hydroxylaminodinitrotoluenes and 2,4,6-triaminotoluene bind irreversibly to soil components, which would prevent or prolong mineralization of the contaminants. Irreversible binding also hinders a further spread of the contaminants through soil or leaching into the groundwater.

Anaerobic treatment of originally contaminated soil from a former ammunition plant was carried out in a laboratory slurry reactor. While fermenting glucose to ethanol, acetate, and propionate, the anaerobic bacteria completely reduced the nitro groups of 2,4,6-trinitrotoluene (TNT) and aminodinitrotoluenes, which led to a complete and irreversible binding of the reduced products to the soil. 2,4-Dinitrotoluene and hexahydro-1,3,5-trinitro-1,3,5-triazine were also reduced in the soil slurry and were no longer detectable after the anaerobic treatment. To mineralize the fermentation products, a subsequent aerobic treatment was necessary to complete the bioremediation process. This bioremediation process was tested in a technical scale at Hessisch Lichtenau-Hirschhagen, Germany. A sludge reactor (Terranox system) was filled with 18 m 3 of contaminated soil (main contaminants were TNT, 2,4dinitrotoluene, hexahydro-1,3,5-trinitro-1,3,5-triazine) and 10 m 3 of water. The anaerobic stage was carried out by periodical feeding of sucrose. The sludge was subsequently dewatered and treated aerobically. Chemical analysis revealed an overall reduction of more than 99% of the contaminants. Ecotoxicological tests performed with various aquatic systems (luminescent bacteria, daphnids, algae) and terrestrial systems (respiring bacteria, nitrifying bacteria, cress plants, earth worms) showed that residual toxicity could not be detected after the anaerobic/aerobic treatment.

No abstract

Während des Zweiten Weltkrieges hat die Produktion und Verarbeitung von 0,8 Millionen Tonnen Trinitrotoluol (TNT) im damaligen Deutschen Reich an vielen Rüstungsstandorten zu Bodenkontaminationen geführt, die heute die Trinkwasserressourcen anliegender Gemeinden gefährden. Bei der Suche nach geeigneten Sanierungsverfahren wurden in den vergangenen Jahren auch mikrobiologische Verfahren geprüft. Dabei wurde eine vollständige Verwertung des TNT als Kohlenstoff- oder Energiequelle bislang nicht nachgewiesen. Bei Zugabe eines leicht verfügbaren Substrates wie Glucose sind aber viele Mikroorganismen in der Lage, die Nitrogruppen cometabolisch über Nitroso- und Hydroxylamino- zu Aminogruppen zu reduzieren