BIOREMEDIATION OF SOLID TNT PARTICLES IN A SOIL SLURRY REACTOR: MASS TRANSFER CONSIDERATIONS

P.C. Gilcrease, V.G. Murphy, and K.F. Reardon, Department of Chemical and Bioresource Engineering and Center for Environmental Toxicology and Technology, Colorado State University, Fort Collins, CO, 80523, Phone: 970-491-5252, FAX: 970-491-7369

ABSTRACT The bioreduction of solid TNT by a Pseudomonas fluorescens strain was investigated in a stirred tank reactor. Experiments in which TNT beads were the only solids present indicated that the biodegradation mechanism is dissolution followed by degradation in bulk solution. Dissolution may limit the overall rate, in which case degradation can be enhanced through increased agitation. Since soil slurries may contain high concentrations of solids other than TNT, Teflon chips were added to investigate two separate effects on TNT dissolution in slurries. First, Teflon solids increase the viscosity of the slurry, resulting in lower solid-liquid mass transfer coefficients. Second, the agitated Teflon slurry can grind or comminute TNT particles, creating additional surface area for mass transfer. Enhanced dissolution rates were observed for TNT beads in a Teflon slurry at higher agitator speeds. This suggests that the biodegradation of solid TNT nuggets in a soil slurry bioreactor may be enhanced under conditions that promote particle attrition.

KEYWORDS: TNT, bioremediation, solids, slurry, dissolution, attrition

This paper is from the Proceedings of the HSRC/WERC Joint Conference on the Environment, May 1996, published in hard copy and on the Web by the Great Plains/Rocky Mountain Hazardous Substance Research Center.

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