Biodegradation of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)

Abstract

Since World War II, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) has been one of the most widely used explosives. Consequently, many munitions facilities and other related sites have been contaminated with HMX and the structurally similar hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). While previous HMX biodegradation studies focused on the anaerobic degradation, these experiments demonstrated that HMX could be degraded in the presence of oxygen by a mixed consortia of acclimated microorganisms when periodically supplemented with carbon and nitrogen. The rapid uptake of carbon and nitrogen resulted in reduced dissolved oxygen levels to 1.0 mg/L within 6 hours of initiation. Over 18 days., HMX transformation rates ranged from 69.8% to 82.3% with performance declining at HMX concentrations of 3.596 [mM and higher. The Monod kinetic parameters, [m-max,, and Ks, were determined to be 1.60 days-' and 0.002 @M, respectively. Data applied to the Andrews model determined the inhibition coefficient, Ki, to be 0. 1 05 [mM. This study evaluated the feasibility of HMX biodegradation under reduced-oxygen conditions.