Biodegradation of RDX and HMX Mixtures: Batch Screening Experiments and Sequencing Batch Reactors

Abstract

Biodegradation is a potential treatment method for the high explosives RDX and HMX. In batch biodegradation tests, a facultative microbial consortium consumed the dissolved oxygen (DO) or reduced the oxidation-reduction potential (ORP) of the culture medium and biodegraded mixtures of RDX and HMX when supplied with various carbon and nitrogen sources. In batch tests with a mixture of carbon sources (glucose, glycerol, and succinic acid), RDX was reduced from 1.1 mg/L to below detectable levels within 4 days in the presence of 0.6 mg HMX/L. With ethanol as the carbon source, the culture degraded 90% of the initial 2.5 mg RDX/L over 8 days in the presence of 0.5 mg HMX/L. In batch mineralization tests, the culture converted 8 and 30% of the initial 14C-RDX to 14CO2 when supplied with ethanol and the mixed carbon sources, respectively. In both cases, a significant fraction of the initial 14C-RDX was converted to water-soluble 14C compounds, indicating triazine ring cleavage. However, mineralization was limit...