Manufacturing and load/assemble/pack (LAP) of insensitive munition (IM) formulations can generate wastewater containing mixtures of legacy and new insensitive high explosives such as 2,4-dinitroanisole (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO), nitroguanidine (NQ), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and ammonium perchlorate. Standard treatment technologies such as biological treatment and granular activated carbon (GAC) are insufficient at removing some IM compounds (e.g., NTO or NQ). The objective of this research was to investigate various treatment trains for the efficient and cost-effective degradation of IM to discharge limits.

Multiple wastewater treatment technologies were evaluated including ion exchange (targeting NTO, ClO4- and NO3-) with regenerate solution treatment for reuse (via oxidation or biological treatment), membrane filtration (for all IM, with subsequent retentate treatment by biological treatment or oxidation), and aerobic granular reactors (for RDX, DNAN, NTO and NQ) and anaerobic granular reactors (for ClO4- and NO3-). Synthetic wastewater was used in each study and data was collected to inform a life cycle assessment.

Critical findings include the following:

• Ion exchange could effectively segregate >98% of NTO, nitrate, and perchlorate from mixed munitions wastewater streams and were regenerable, extending the sustainability of the technology.
• Oxidation via UV/H₂O₂ or ozone nanobubbles was effective at treating >99% of NTO in the regenerant solution from ion exchange columns.
• Reverse osmosis effectively rejected >96% of NTO, RDX, DNAN and NQ, but rejection was impacted by the presence of co- and counter-ions and wastewater pH.
• Aerobic granular reactors, degraded DNAN and NTO (>98%), but only 40 to 70% of RDX and NQ over 700 days.
• Anoxic fast settling sludge reactors degraded >97% of nitrate and perchlorate over 500 days.
• A life cycle assessment of different combinations of the segregation and treatment technologies indicated that the most sustainable alternatives compared to the baseline GAC treatment included IX with regeneration via hydrochloric acid, biodegradation by AxGS, and ozone oxidation. This train had 94% less environmental impact (across Tool for the Reduction and Assessment of Chemical and other Environmental Impacts categories except ozone depletion) than GAC treatment over 13 years of operation.

Overall, the results of this study indicated that multiple different technologies were suitable for IM wastewater treatment with some technologies (i.e., IX with regeneration and aerobic granular sludge) potentially being more sustainable than others. Therefore, multiple technologies could be considered cost effective alternatives to the baseline GAC treatment commonly employed for insensitive high explosives treatment. However, additional studies using real IM wastewater from various facilities is required through bench and pilot studies before a suitable approach can be designed for manufacturing, LAP, and demilitarization facilities. Results from this research will directly strengthen the Department of Defense’s operational readiness and ensure warfighter preparedness. (Project Completion - 2023)