Enhanced Aerobic Biodegradation of Soil Contaminated with Explosives (TNT and PETN) By Rhamnolipid

Abstract

The aim of this study was to investigate the bioremediation of two explosives 2, 4, 6-trinitrotoluene
(TNT) and Pentaerythritol Tetranitrate (PETN) in mixture by aerobic process. Microbial inocula were
obtained from a textile wastewater treatment plant activated sludge. Addition of rhamnolipid
surfactant (60 mg/l) increased the removal efficiencies of TNT and PETN from 53% and 57% to 98%
and 91%, respectively. Explosives degradation reaction is expressed to be of first-order and the
kinetic reaction parameters are calculated based on different initial concentrations of TNT and PETN.
The first-order rate constants of the rhamnolipid amended experiments were at least 3 orders and 2.5
orders of magnitude higher for TNT and PETN, respectively, than those found for not amended
rhamnolipid experiments. The metabolites pentaerythritoldinitrate,3-hydroxy-2,2-bis
[(nitrooxy)methyl]propanal,and2,2-bis-[(nitrooxy)methyl]-propanedialfor PETN and2-amino-4, 6-
dinitrotoluene and 4-amino-2, 6-dinitrotoluene for TNT were identified by LC-MS. Concomitant
degradation of TNT and PETN resulted in decrease of environment pH. Inoculated bacteria have
capability to use of explosive as source of nitrogen and energy. It seems that the addition of
rhamnolipid showed great potential for treatment of explosives by textile activated sludge.