Stimulating the anaerobic biodegradation of explosives by the addition of hydrogen or electron donors that produce hydrogen

The anaerobic biodegradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7tetrazocine (HMX), and 2,4,6-trinitrotoluene (TNT) by a methanogenic mixed culture was investigated. Microcosms containing a basal medium and the mixed culture were amended with ethanol, propylene glycol (PG), butyrate or hydrogen gas as the electron donor and a mixture of TNT (50 (mu)M), RDX (25 (mu)M), and HMX (8 (mu)M). After 29 days TNT and RDX were completely transformed to unidentified endproducts in the bottles amended with ethanol, hydrogen, or PG, while 53%, 40%, and 22% of the HMX was transformed, respectively. There was no loss of RDX or HMX in the electron donor unamended control bottles. The ethanol and PG were transformed to near stoichiometric amounts of acetate and propionate, suggesting the immediate electron donor supporting the transformation of the explosives was the H2 evolved during the metabolism of the parent substrate. Our findings suggest that the addition of H2 or electron donors that produce H2 may be a useful strategy for enhancing the anaerobic biodegradation of explosives in contaminated groundwater and soils.