Improvement of biodegradability of explosives using anaerobic-intrinsic bioaugmentation approach

Abstract

A successful anaerobic intrinsic bioremediation (bioaugmentation) was carried out on 2,4,6-trinitrotoluene (TNT) and Pentaerhytritol tetranitrate (PETN) contaminated soil, using indigenous bacteria. Two soil pans were enriched by sewage sludge and one pan was mixed by monorhamnolipid biosurfactant both of which are economically suitable substrates for anaerobic in situ explosive bioremediation. Preliminary concentrations of TNT and PETN were 1000 and 200 mg/kg. The results of this study showed that in order to increase the explosives degradation with more resistant to biodegradation such as PETN, the usage of biosurfactant could be effective. Inoculation of indigenous bacteria had a significant effect on TNT and PETN remediation efficiency and increased them to 99.1 and 91 in the presence of biosurfactant. Seven indigenous strains were identified as Planomicrobacterium flavidum, Pseudomonas auroginosa, Entrobactor asburiae, Azospirillium, Rhizobium, Methylobacterium and Pseudomonas denitrificant strains. It is logical that these isolates may have potential for TNT and PETN degradation. Monorhamnolipid might be effective in the improvement of explosives degradation due to impact on the cell membrane of bacteria. The results of this study have shown that intrinsic bioremediation has the potential to reduce the time and costs for in situ explosive bioremediation.