Screening Effective Factors in Slurry Phase Bioremediation of TNT Contaminated Soils

Explosive contaminated soils are recognized as a major environmental issue due to the toxic and mutagenic effects of these energetic materials. Particularly, 2,4,6-trinitrotoluene (TNT), a common military explosive, has a main role in explosive contaminated soils. Bioremediation has recently emerged as an alternative solution to conventional physical and chemical methods for treatment of organic contaminant such as TNT. In this work, after selection of the superior bacterium among four bacteria in aqueous phase, slurry phase bioremediation of clay soil contaminated with 1000 mg/kg TNT was carried out in shaking flasks, showing the maximum potential of 97% TNT removal by this bacterium after 25 days. As a first step in TNT elimination optimization in slurry phase, the effective factors have been screened via the two-level fractional factorial design method plus three center points using seven factors i.e., glucose (0.2, 8%), yeast extract (0, 0.02%), (NH4)2SO4 (0.01, 0.05%), Tween80 (0.1, 0.5%) and slurry concentrations (20, 40%) as well as inoculum size (5, 10%) and temperature (20, 35˚C) during 15 days. It was found that slurry, surfactant and glucose concentrations and inoculum size are the significant factors. In addition, cross (mutual interaction) interactions of glucose with other effective factors were considerable.

Keywords:

Bioremediation , Explosive , Fractional factorial design , Slurry phase , TNT