Simulated bio-slurry reactor for bioremediation of highly contaminated soils by 2,4,6-trinitrotoluene (TNT)

Abstract

The widespread use of 2,4,6-trinitrotoluene (TNT) in military sites causes serious soil contamination problems. In this study, various additions of glucose, glycerol, and activated sludge were tested under laboratory conditions in a simulated bio-slurry reactor for bioremediation of soil from highly TNT-contaminated sites. The results showed that the addition of both glucose and glycerol as electron donors could efficiently promote microbial degradation of TNT. The co-addition of glycerol and sludge resulted in 65.2% total removal of TNT in the soil (2.76 × 102 mg/kg) and 79.8% total removal of TNT in the soil (1.35 × 102 mg/kg), respectively. After 39 days of incubation with glucose and sludge, the removal of TNT reached 86.3% in the most seriously polluted soil (2.83 × 103 mg/kg). 16S rRNA sequencing for bacteria showed that the addition of glucose and glycerol significantly stimulated the growth of Enterobacteriaceae and Pseudomonas populations, respectively, which dominated the post-degradation soil microbial community. The bioavailability concentration of TNT extracted with (2-Hydroxypropyl)-β-cyclodextrin (HPβCD) rapidly decreased to very low levels during remediation seems to provide an explanation for complete degradation of TNT could not be achieved even in soils with relatively lower contamination. In addition, adequate electron donors are necessary to ensure the sustainable bioremediation of TNT-contaminated soil with high concentrations compared to surfactant. This work suggests that co-addition of glycerol (or glucose) and sludge is a desirable strategy for aerobic bioremediation of sites contaminated with high concentrations of TNT.