Use of hexahydro-1,3,5-trinitro-1,3,5-triazine as a nitrogen source in biological treatment of munitions wastes

The purpose of this study was to develop a biological treatment process for die degradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), a nitram ine explosive present in munitions manufacturing and processing wastes. A r eal waste mixture containing RDX, nitrate and nitrite (NOx), and several so lvents (primarily cyclohexanone and acetone) was used as basic feed for ben ch-scale experiments. Pare culture experiments indicated that bacteria can use RDX as a nitrogen source and organic solvents as carbon sources under a erobic conditions. In addition, it has been found that inorganic nitrogen c ompounds might interfere with the use of RDX as a nitrogen source. Because NOx are problematic constituents that should be removed anyway, anaerobic m icrobial denitrification was applied as a pretreatment stage to simultaneou sly remove NOx and organics and to form a nitrogen-deficient environment fo r further aerobic degradation of RDX and residual organics. This conceptual approach was performed using two reactor systems: a two-stage anaerobic-ae robic system and a single reactor with anaerobic and aerobic stages in its operation cycle. All laboratory reactors were operated in the sequencing ba tch reactor mode. Both systems achieved complete NOx removal in the denitri fication stage with acetone serving as the carbon source and complete aerob ic biodegradation of RDX with cyclohexanone serving as the carbon source.