Effect of Monorhamnolipid Contribution on Anaerobic-Natural Attenuation of Explosives in Contaminated Soils

At least 90% of the research on bioremediation has been based on the use of materials in cometabolism and/or as electron donors. The main purpose of this study was to evaluate biodegradation rates of explosives in soil in terms of economics and feasibility. Two lab-scale bioreactors were operated in this study, and results showed biodegradation rates of 2,4,6-trinitrotoluene (TNT) and pentaerythritol tetranitrate (PETN) at 84 and 67% after 60days compared with rates of 46 and 29% without the monorhamnolipid contribution. Chemical oxygen demand (COD) was monitored during bioremediation and showed that reduction in COD concentration was directly proportional to desorption of intermediates from the soil matrix and their degradation, along with degradation of the parent compounds. Results also showed that the anaerobic condition for nitroaromatic bioreduction as the sole source of nitrogen was time consuming. The monorhamnolipid overcomes this challenge via enhanced biodegradation efficiency of nitroaromatics. Furthermore, application of the monorhamnolipid as in situ explosive bioremediation is feasible, suitable, environmentally friendly, and economical, especially in hot and wet areas with extensive contamination.