ABSTRACT
The present study explores the feasibility of biotreatment of 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro- 1,3,5-triazine (RDX)-contaminated soils in slurry batch reactors. Radiorespirometric assays showed that anaerobic sludge was able to mineralize 59% RDX to CO2 although significant mineralization of TNT was not observed in all cases. TNT and RDX at concentrations higher than 50 and 100 mg/L respectively were inhibitory to methanogenesis (used as a bioindicator), however, methanogenesis recovered after TNT was transformed into less toxic triaminotoluene. Bioslurry batch reactors containing 40% of contaminated soil (2000 mg RDX and 1000 mg TNT/kg dry soil) were operated under various conditions. Both TNT and RDX were persistent to soil indigenous microbes. Degradation of both TNT and RDX was enhanced by the municipal sludge amendment, although degradation of RDX was only achieved under anaerobic conditions.
Subject(s)
Bioreactors/microbiology , Soil Pollutants/isolation & purification , Aerobiosis , Anaerobiosis , Biodegradation, Environmental , Explosions , Sewage , Soil Microbiology , Soil Pollutants/metabolism , Triazines/isolation & purification , Triazines/metabolism , Trinitrotoluene/isolation & purification , Trinitrotoluene/metabolismABSTRACT
p-Cresol was repeatedly detected as a trace metabolite in anaerobic slurry reactors treating 2,4,6-trinitrotoluene (TNT)-contaminated soils. This study shows that p-cresol was not a metabolite of the anaerobic degradation of TNT, by using a combination of analytical techniques and 13C-labelled TNT. Instead, p-cresol, an intermediate in the degradation pathway of some amino acids, was shown to be inhibited by TNT and its metabolites. The range and persistence of inhibition to p-cresol microbial degradation decreased with the level of amino-substitution of the derivatives. This explains why p-cresol accumulated within the TNT-treating anaerobic bioslurry, as it could not be further biodegraded in the presence of TNT.
