Bioremediation of RDX and HMX contaminated soil employing a biochar-based bioformulation

Abstract

Compounds like Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and Octahydro-1, 3, 5, 7-tetranitro-1, 3, 5, 7-tetrazocine (HMX) are categorised as a secondary explosive. These secondary explosives are widely employed for defence and civil purposes worldwide. The release of explosive compounds in the environment during their production, storage and usage results in severe soil and water contamination. Pollution caused by explosives is a major concern as it is recalcitrant in nature and has toxic effects on human beings, animals and plants. There is a need to find an eco-friendly and sustainable approach to deal with explosive contaminated soil. In the present study, bioformulation was prepared with explosive degrading bacteria to treat explosive contaminated soil. Bioformulation consisted of coconut husk-derived biochar as a carrier material and Arthrobacter subterraneus as an active ingredient. The survivability of bacteria and performance of bioformulation with different concentrations of explosive compounds were analysed. Results showed that Arthrobacter subterraneus could immobilise with biochar and can survive up to 6 months. The prepared bioformulation was able to degrade up to 85.98% RDX and 80.4% HMX in contaminated soil in a time duration of 30 days. A significant increase in nitrite concentration, a major byproduct of RDX and HMX biodegradation, was found in soil treated with bioformulation. Thus, bioformulation can be applied to remediate explosive-contaminated sites as an eco-friendly technique. Graphical Abstract