Biodegradation of 2,4-and 2,6-Dinitrotoluene by Freshwater Microorganisms

The microbial degradation of 2,4- and 2,6-dinitrotoluene was complete or nearly complete in surface water from two locations downstream from the Radford Army Ammunition Plant. No degradation was detected in surface water from four local (Frederick, Md area) sites. Either isomer could serve as a sole carbon and energy source, with about 60 percent of substrate carbon appearing as CO2, and with an increase in the population of degrading organisms. In both the rate of mineralization in percent degraded per day increased with increasing substrate concentration. At 10 mg/l, degradation rates of 32 and 14.5 percent/ day were observed for the 2,4 and 2,6 isomers, respectively. At very low concentrations of the 2,6 isomer a degrading population did not develop, and significant degradation did not occur. The rate of substrate utilization was far greater for the 2,4 isomer; this is consistent with the far greater density of 2,4-DNT degraders in the water. A much shorter lag time was also encountered with 2,4-DNT.