Aerobic biodegradation of 2,4-dinitrotoluene, aminonitrotoluene isomers, and 2,4-diaminotoluene

2,4-Dinitrotoluene (DNT) is widely used in industry, including the manufacture of propellants. 2,4-Diaminotoluene (DAT), 2-amino-4-nitrotoluene (2A4NT), and 4-amino-2-nitrotoluene (4A2NT) are among the products that can result from biological treatment of DNT. The objective of this study was to examine the biodegradability of these hazardous compounds. Using an inoculum from a munitions wastewater treatment plant, enrichment cultures were developed that readily consumed DAT, 4A2NT, 2A4NT, and DNT when they were provided as sole organic substrates (84-100 mg 1(-1)) or when ethanol (600 mg 1(-1)) was added as a cosubstrate. Low effluent chemical oxygen demand (COD) levels suggested that the aromatics were mineralized, rather than simply transformed to other possibly hazardous compounds. The addition of ether (142 mg 1(-1)) as a cosubstrate had no significant effect on the biodegradation of DAT and 4A2NT, but did inhibit the consumption of DNT and 2A4NT. The presence of ether in munitions wastewater may therefore present a challenge to effective biological treatment. When DNT was added to enrichment cultures as sole substrate, nitrite was released stoichiometrically. However, when ethanol was also added, nitrite release was only 59% of the maximum, indicating that most of the DNT was reduced prior to ring cleavage. When provided to enrichment cultures as the sole substrates, the observed yield coefficients for the aromatic compounds ranged from 0.10 to 0.28 mg of volatile suspended solids per mg COD.