Modeling of Complex Reductive Biodegradation Kinetics of Recalcitrant Organic Contaminants

A kinetic model based on the Michaelis-Menten kinetic equations for simulating the complex reductive biodegradation kinetics of groundwater contaminants was developed that incorporates multiple levels of branching via the formation of multiple daughter products from a parent compound and/or a daughter product from multiple parent compounds. The model was tested using experimental data from two published laboratory studies involving the biodegradation of 2,4,6-trinitrotoluene (TNT) in the presence and absence of sorption. In each case, reasonable correlation was observed between the model-calculated and experimentally observed concentrations of TNT and its biodegradation products and the total mole balance with time. Model calibration-determined maximum specific rates of biodegradation were found to decrease with increasing substitution of nitro groups by amino groups from TNT to 2,4,6-triaminotoluene via aminodinitrotoluenes (ADNTs) and diaminonitrotoluenes (DANTs). Biodegradation of DANTs was also found to be strongly inhibited by the presence of parent intermediates ADNTs. The maximum specific rates of biodegradation for TNT and products were found to decrease in the presence of sorption.