Effective treatment of energetic containing wastewater in a sequential anaerobic-aerobic membrane bioreactor (MBR) system - Part 1: Treatment of IMX-104 wastewater

Abstract

The treatment of wastewater containing the new insensitive energetic formulation IMX-104, which consists of the legacy explosive RDX and insensitive high explosives (IHE), 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-triazole-5-one (NTO), was evaluated using a dual anaerobic-aerobic membrane bioreactor system. RDX and DNAN in the wastewater were completely degraded in the anaerobic MBR, with no observed production of common reduced daughter products (e.g., MNX, DNX or TNX for RDX and 2-ANAN, 4-ANAN, and DAAN for DNAN). NTO concentrations as high as 2 g L⁻¹ were biotransformed predominantly to 3-amino-1,2,4-triazole-5-one (ATO) in the anaerobic MBR. The ATO degrading capacity of the aerobic MBR was exceeded at the high NTO concentrations, but subsequent polishing with 5 % sodium hypochlorite (∼4000 mg L⁻¹ free chlorine) resulted in complete ATO removal. Electrochemical oxidation and UV/H₂O₂ treatment was also demonstrated to be effective for removal of residual ATO. The dual MBR system was fed a broader mixture of munitions constituents during some phases of operation, including HMX, TNT, nitroguanidine (NQ), perchlorate, and nitrate, and was observed to biodegrade these compounds even after a 90-day period when they were absent from the influent (i.e., during IMX-104 treatment). The dual MBR with sodium hypochlorite polishing proved to be highly effective for treatment of IMX-104 wastewater, as well as for removal of a variety of other munitions constituents.