| Abstract
| - Mixtures of 2,4- and 2,6-dinitrotoluene are produced inlarge quantities as precursors of polyurethane foams andthe explosive 2,4,6-trinitrotoluene (TNT). The twoisomersare widely distributed in contaminated groundwater andsoil.Bacteria capable of growing with the individualisomersas the sole source of carbon, nitrogen, and energy havebeen isolated previously. However, attempts todegrade2,4- and 2,6-DNT simultaneously have failed. We testedthehypothesis that a mixed culture could degrade an isomericDNT mixture if the bacteria were grown in an aerobicbiofilm at low substrate concentrations. Suchconditionswere achieved with a fluidized-bed biofilm reactor (FBBR).The reactor was fed aqueous solutions containing 2,4-(40mg L-1) and 2,6-DNT (10 mgL-1). The feed flow ratewasgradually increased to yield surface loading rates of 36−600 mg of DNT m-2d-1. Removal efficiencies higherthan98% for 2,4-DNT and 94% for 2,6-DNT were achieved atall loading rates. The nitrogen released from DNT wasfoundquantitatively as nitrate that indicated the presence ofnitrite-oxidizing bacteria. COD measurements of thereactoreffluent confirmed complete mineralization of the DNT.The results demonstrate that mixtures of 2,4- and2,6-DNTcan be biodegraded successfully in an aerobicFBBR.
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