Bioaugmentation for remediation of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) contaminated soil using a clay based bioformulation

Bioaugmentation is an important remediation strategy for hazardous organic compounds. A microcosm study was conducted to evaluate the remediation of soils contaminated with hazardous high explosive, Octahydro1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) using an eco-friendly bioformulation. Janibacter cremeus, an enriched indigenous soil bacterium isolated from the explosive contaminated site was immobilized in a mixture of calcite and cocopeat for bioaugmentation. The developed bioformulation showed a consistent viability for 150 days, at 4 degrees C storage conditions. HMX at field concentrations was degraded in microcosms for 35 days under unsaturated (aerobic) and saturated (anoxic) moisture conditions. Negligible degradation was observed under unsaturated moisture conditions, whereas, saturated conditions led to substantial decrease in HMX. Mass spectrometric (MS) analysis revealed the formation of nitroso derivatives of HMX during the anoxic degradation. Also, observed was the presence of 5-hydroxy-4-nitro-2,4-diazapentanal, a precursor of 4- nitro-2,4-diazabutanal, which eventually could be mineralized. An inexpensive and natural carrier when chosen for immobilization of explosive degrading microbes was found to be effective in the in situ remediation of explosive.