Effect of food-grade surfactant on bioremediation of explosives-contaminated soil.

The use of native soil bacteria to biodegrade explosives-contaminated soil under co-metabolic conditions has been demonstrated. The addition of food-grade surfactants could improve the process by enhancing the rates of explosives desorption from soil, thereby increasing the bioavailability of explosives for microbial degradation. The objective of this study was to decrease residence time in the slurry reactor, thereby increasing output and reducing clean-up costs. In this study, Tween 80 (monooleate), served not only as a surfactant but also as the carbon substrate for the soil microorganisms. Four 2l soil slurry reactors were operated in batch mode with soil containing 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). The results indicated that TNT and RDX were 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 CO2.