Interpretation and modeling of slurry reactor performance to provide monitoring strategies for the aerobic bioremediation of dinitrotoluene-contaminated soils

In a previous study, pilot-scale bioslurry reactors were used to treat soils highly contaminated with 2,4-dinitrotoluene (2,4-DNT) and 2,6-dinitrotoluene (2,6-DNT). The treatment scheme involved a soil washing process followed by two sequential aerobic slurry reactors augmented with DNT mineralizing bacteria. This previous work found that constant monitoring was necessary to avoid long lag periods upon refeeding. In this study, it was determined that the heterogeneous distribution of soil in the reactor deleteriously impacted direct monitoring of DNT concentrations. Instead, the use of nitrite production or NaOH consumption as surrogate monitoring parameters proved to be more accurate predictors of reactor performance. A model was developed to predict the distribution and biodegradation of DNT in the reactors. Analysis of model results showed that the maximum substrate utilization rate controlled DNT degradation rates in the reactor, a population shift occurred after approximately 26 days, and phosphorous was limiting at high solids loading rates