CHARACTERIZATION OF PRODUCTS FROM THE BIOTRANSFORMATION OF 2,4-DINITROTOLUENE BY DENITRIFYING ENRICHMENT CULTURES

Anoxic biotransformation of 2,4-dinitrotoluene (DNT) was examined and two denitrifying enrichment cultures were developed. In one, the inocu lum was acclimated to treatment of munitions wastewater that contains DNT; the other was derived from activated sludge that was not routinel y exposed to nitroaromatics. DNT was consumed readily by both cultures only when ethanol was provided as a primary substrate, with the rate of transformation twice as fast in the acclimated culture. [C-14]DNT w as used to track the metabolites. A negligible amount of the DNT was m ineralized. The principal initial biotransformation pathway was reduct ion of DNT to aminonitrotoluenes. Subsequent transformations in the ac climated culture resulted in formation of 6-nitroindazole, 2-nitrotolu ene, and 4-nitrotoluene, which have not previously been reported as me tabolites from DNT. Acetylation at the para position was another impor tant transformation pathway in the acclimated culture, resulting in ac cumulation of 4-acetamide-2-nitrotoluene and 4-acetamidetoluene. Reduc tion of aminonitrotoluenes to 2,4-diaminotoluene also occurred, follow ed by conversion of approximately one-third of the C-14 activity to no nfilterable material. The majority of the soluble DNT metabolites from the unacclimated culture were hydrophilic; these were characterized b y gradient elution high-pressure liquid chromatography analysis and io n pairing chromatography as approximately equal amounts of negatively charged and neutral compounds. The diversity and characteristics of th ese metabolites indicates that biotransformation of DNT under anoxic c onditions does not necessarily eliminate the toxicological hazards ass ociated with the parent compound. Metabolite formation should be taken into consideration when determining discharge criteria for DNT-contam inated wastewaters exposed to denitrifying environments.