REMOVAL OF TNT AND HETEROCYCLIC NITRAMINES IN WASTEWATER USING ELEMENTAL IRON AND H2O2

2,4,6-Trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) are common explosives and major constituents in wastewater from munitions-manufacturing plants (pink water). Conventional biological and chemical oxidation processes were not efficient to treat pink water because electron withdrawing nitro constituents in explosives inhibit the oxidation. Consequently, costly granular activated carbon (GAC) sorption process has been used as a standard process for pink water treatment. We hypothesized that reduction with elemental iron will make refractory explosives more easily oxidizable compounds and enhance the extent and rate of degradation in Fenton oxidation. In the present study, we examined the enhancement of degradation due to pretreatment with elemental iron in oxidation of TNT and RDX in a laboratory-scale continuous stirred tank reactor (CSTR) with Fenton's reagent. Results showed that iron pretreatment enhanced the extent of TOC removal by approximately 20% and 60% for TNT and RDX, respectively. 100% of TOC removal was achieved for TNT and RDX with iron pretreatment under relatively mild oxidation conditions. However, in direct oxidation of TNT and RDX with Fenton's reagent, complete TOC removal in the CSTR was not observed with much higher H2O2 and Fe2+ concentrations. These results suggest that the reduction products of TNT and RDX are more rapidly and completely oxidized by Fenton's reagent and that a sequential iron treatment – Fenton oxidation process may be a viable technology for pink water treatment.