Improving Mathematical Model in Biodegradation of PAHs Contaminated Soil Using Gram-Positive Bacteria

In published literature there are limited studies on the estimation of kinetic parameters of polycyclic aromatic hydrocarbons (PAHs) in soil. In addition, neither the kinetic studies were performed with Gram-positive bacteria nor conducted under non-indigenous condition in order to understand their removal performance. Thus, a mathematical model describing biodegradation of phenanthrene-contaminated soil by Corynebacterium urealyticum, bacterium isolated from municipal sludge, was developed in this study. The model includes three kinetic parameters that were determined using TableCurve 2D software, namely qmax (maximum substrate utilization rate per unit mass of bacteria), X (biomass concentration) and Ks (substrate concentration at one half the maximum substrate utilization rate). These parameters were evaluated and verified in five different initial phenanthrene concentrations. Highest degradation rate was determined to be 79.24 mg kg^?1 day^?1 at 500 mg kg^?1 initial phenanthrene concentrations. This high concentration shows that bacteria perform better in contaminated sand compared to liquid media. High r² values, ranging from 0.92 to 0.99, were obtained excluding 1000 mg/kg phenanthrene. The kinetic parameters, i.e., qmax and Ks, increased with the phenanthrene concentration and thus suggest that bacteria degrade at a higher degradation rate. This model successfully described the biodegradation profiles observed at different initial phenanthrene concentrations. The established model can be used to simulate the duration of phenanthrene degradation using only the value of the initial PAHs concentration.