Biological transformation of 2,4-dinitrotoluene under denitrifying conditions
Noguera Camacho, Daniel Ricardo
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Permalink
https://hdl.handle.net/2142/22491
Description
Title
Biological transformation of 2,4-dinitrotoluene under denitrifying conditions
Author(s)
Noguera Camacho, Daniel Ricardo
Issue Date
1996
Doctoral Committee Chair(s)
Freedman, David L.
Department of Study
Civil and Environmental Engineering
Discipline
Civil and Environmental Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Microbiology
Engineering, Civil
Engineering, Environmental
Language
eng
Abstract
The anoxic biotransformation of 2,4-dinitrotoluene (DNT) was evaluated. Two denitrifying enrichment cultures were developed, one with inoculum from the biological treatment plant at Radford Army Ammunition Plant (RAAP), which was acclimated to treatment of DNT munitions wastes, the other derived from an activated sludge not routinely exposed to nitroaromatics (Urbana). DNT was cometabolically transformed by both cultures when an external carbon source was supplied. Initial transformations were reductive, with the transient accumulation of 2-amino-4-nitrotoluene, 4-amino-2-nitrotoluene, and 2,4-diaminotoluene. In addition, formation of 2-nitrotoluene and 4-nitrotoluene occurred by reductive deamination of the corresponding aminonitrotoluenes. 6-Nitroindazole was also identified as a significant metabolite from DNT in both cultures. A radioactive $\rbrack\sp{14}\rm C\lbrack$-DNT tracer, used to track the fate of the DNT, revealed that DNT was not mineralized in either culture. In addition, a significant fraction of the original DNT was transformed to insoluble products (33-40%), possibly by polymerization of 2,4-diaminotoluene. Furthermore, there was a significant difference in the composition of the soluble products from each culture. In the Urbana enrichment, most of the soluble products were hydrophilic, while in the RAAP enrichment, the majority of the products were hydrophobic. Ion pairing chromatography was used to partially characterize hydrophilic products in the Urbana enrichment. Approximately equal amounts of negatively charged and neutral compounds were detected. Mass spectroscopy of the hydrophobic products in the RAAP enrichment indicated the presence of the acetylated metabolites 4-acetamidetoluene and 4-acetamide-2-nitrotoluene.
A strain of Pseudomonas aeruginosa (strain LCA) was isolated from the RAAP enrichment and evaluated for its ability to biotransform DNT and other nitrotoluenes. Reduction of nitro groups to amines and N-acetylation were the most important transformations. Although reduction and acetylation of the nitro groups located ortho and para to the methyl moiety was possible, acetylation at the para position was the fastest reaction, while acetylation at the ortho position was kinetically unfavorable.
The results from this research demonstrated that denitrification alone was not a satisfactory biological process for the treatment of DNT in munitions wastes, because mineralization did not occur and the products identified exhibited similar toxicological concerns as DNT.
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