Mathematical Modeling of Nitrification in Mixed Cultures: Insights into Nitrite-Oxidizing Bacteria Growth and Ammonia Starvation Effect

Abstract

Nitrification, a crucial process in wastewater treatment, involves the conversion of ammonium nitrogen to nitrate nitrogen through the sequential activities of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB). In the present study, a comprehensive mathematical model was developed to describe the nitrification process in mixed cultures involving isolated NOB and starved AOB. The growth equation for NOB was divided into anabolism and catabolism, elucidating the key substrates driving their metabolic activities. Considering the ammonia starvation effect, a single cell-based model was developed to capture the mass transfer phenomena across the AOB cell membrane. This addition allowed for a more accurate representation of the biological dynamics during starvation conditions. The model’s accuracy was tested using experimental data that was not used in the model calibration step. The prediction’s coefficient of determination (R2) was estimated at 0.9. By providing insights into the intricate mechanisms underlying nitrification, this model contributes to the advancement of sustainable wastewater treatment practices.