Selecting the best electron donor and operational temperature for the rapid biotransformation of the insensitive munitions compound 2,4-dinitroanisole (DNAN) by anaerobic sludge

Abstract

Abstract 2,4-Dinitroanisole (DNAN) is a toxic compound increasingly used by the military that can be released into the environment on the soil of training fields and in the wastewater of manufacturing plants. DNAN's nitro groups are anaerobically reduced to amino groups by microorganisms when electron donors are available. Using anaerobic sludge as the inoculum, we tested different electron donors for DNAN bioreduction at 20 and 30 °C: acetate, ethanol, pyruvate, hydrogen, and hydrogen + pyruvate. Biotic controls without external electron donors and abiotic controls with heat-killed sludge were also assayed. No DNAN conversion was observed in the abiotic controls. In all biotic treatments, DNAN was reduced to 2-methoxy-5-nitroaniline (MENA), which was further reduced to 2,4-diaminoanisole (DAAN). Ethanol or acetate did not increase DNAN reduction rate compared to the endogenous control. The electron donors that caused the fastest DNAN reductions were (rates at 30 °C): H2 and pyruvate combined (311.28 ± 10.02 μM·d−1·gSSV−1), followed by H2 only (207.19 ± 5.95 μM·d−1·gSSV−1), and pyruvate only (36.35 ± 2.95 μM·d−1·gSSV−1). Raising the temperature to 30 °C improved DNAN reduction rates when pyruvate, H2, or H2 + pyruvate were used as electrons donors. Our results can be applied to optimize the anaerobic treatment of DNAN-containing wastewater.