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, 6dinitrotoluene 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.