THEORETICAL EVALUATION OF DISSOLUTION AND BIOCHEMICAL REDUCTION OF TNT FOR PHYTOREMEDIATION OF CONTAMINATED SEDIMENTS

In this study the removal of 2,4,6-trinitrotoluene (TNT) in the subsur face was theoretically simulated using a steady-state one-dimensional form of the advection-dispersion-reaction (ADR) equation, also account ing for TNT dissolution. The system studied consists of equal-sized sp herical TNT particles uniformly distributed in an anaerobic saturated sediment. Water is assumed to flow steadily and uniformly through the sediment. The TNT removal is accomplished by biochemical catalysts (en zymes) released by plants. A sensitivity analysis was performed by var ying TNT particle diameter, soil TNT content, Darcy velocity and a fir st-order biochemical reduction rate constant, and studying their effec t on the TNT aqueous-phase concentration and TNT removal rate from the exposure zone. With zero or low biochemical reduction rate constants, it was found that the rate of removal of TNT from the exposure zone i mproved with higher flushing rates. On the other hand, higher biochemi cal reduction rate constants resulted in significant reduction of the aqueous TNT concentration at all flushing rates and in higher TNT remo val rates from the exposure zone. A biochemical reduction rate constan t of 14.25 day(-1) was measured for reduction of dissolved TNT by sedi ments containing biochemical catalysts under anaerobic conditions. A s imulation using this rate constant suggested the feasibility of in sit u phytoremediation of TNT-contaminated sediments.