PHYTOTREATMENT OF TNT-CONTAMINATED GROUNDWATER

Phytoremediation is a viable technique for treating nitroaromatic comp ounds, particularly munitions. Continuous flow phyto-reactor studies w ere conducted at the following three influent concentrations of 2,4,6- trinitrotoluene (TNT): 1, 5, and 10 ppm. A control was also prepared w ith an influent TNT concentration of 5 ppm. Flow rates were systematic ally reduced to increase hydraulic retention times (HRT) which ranged from 12 to 76 days. initially, the control reactor removed TNT as effi ciently as the plant reactors. With time, however, the efficiency of t he control became less than that of the plant reactors, suggesting tha t adsorption was initially the mechanism for removal. Up to 100% of th e TNT was removed. Aminodinitrotoluene (ADNT) effluent concentration w as higher for higher TNT influent concentrations. Increasing the reten tion time reduced ADNT concentration in the effluent. Supplementary ba tch studies confirmed that ADNT and diaminonitrotoluene (DANT) were ph ytodegraded. Preliminary batch studies were also conducted on the degr adation of RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) and HMX(Octah ydro-1,3,5,7-tetranitro-1,3,5, 7-tetraazocine). These batch studies in dicated that the degradation of RDX was slower than that for TNT. A st udy with HMX indicated that the removal rates were reasonable, but req uired a lag phase.