RDX DEGRADATION WITH BIO AUGMENTED Fe~0 FILINGS: IMPLICATIONS FOR ENHANCED PRB PERFORMANCE

摘要

Hexahydro-l,3,5-trinitro-l,3,5-triazine (RDX) degradation was studied in aquifer microcosms amended with Fe~0 flings. Faster removal occurred in treatments with Fe~0 plus anaerobic sludge, and agitation significantly increased RDX degradation rates. The nitroso byproducts l,3-dinitro-5-nitroso-l,3,5-triazacyclohexane (MNX), l,3-dinitroso-5-nitro-l,3,5-triazacyclo-hexane (DNX), and l,3,5-trinitroso-l,3,5-triazacyclohexane (TNX) were detected in both bioaugmented and abiotic microcosms, although these compounds never accumulated above 5% of the added RDX on a molar basis. [~(14)C]-RDX was synthesized for additional fate studies. Microcosms with both Fe~0 and sludge mineralized RDX faster and to a greater extent than separate treatments, with up to 51% ~(14)CO_2 recovery after 77 days. A soluble (unidentified) metabolite was found in all microcosms, and this compound accumulated to a much lower extent in combined-treatment reactors than in sets with Fe~0 or sludge alone. Some of the radiolabel was bound to soil and Fe~0 and could not be extracted with CH_3CN. This fraction, which was recovered by combustion with a biological oxidizer, was also found at lower concentrations in combined-treatment reactors. This work suggests that permeable reactive Fe~0 barriers (PRBs) might be an effective approach to intercept and degrade RDX plumes, and that treatment efficiency might be enhanced by biogeochemical interactions through bioaugmentation.