Surfactant-enhanced bioremediation of soil contaminated with 2,4,6-trinitrotoluene in soil slurry reactors

The addition of food-grade surfactants could improve the use of native soil bacteria to biodegrade explosives-contaminated soil under co-metabolic conditions by enhancing the rates of explosives' desorption from soil, thus increasing the bioavailability of explosives for microbial degradation. The objective of this study is to decrease residence time in the reactor, thereby increasing output and reducing cleanup costs. In this study, Tween 80 (monooleate) served not only as a surfactant but also as the carbon substrate for soil microorganisms. Four 2-L soil slurry reactors were operated in batch mode with soil containing 2,4,6-trinitrotoluene (TNT). Results indicated that TNT was removed in all reactors except the control (no added carbon source). The reactor enriched with surfactant and molasses performed better than reactors with either molasses or surfactant alone. The TNT and its metabolite, 4-amino-2,6-dinitrotoluene, were removed faster in the reactor with surfactant plus molasses (35 days) than in the reactor with molasses alone as carbon source (45 days). A radiolabeling study of the mass balance of TNT in the slurry reactors showed substantial mineralization of TNT to carbon dioxide.