Modeling N2O production by ammonia oxidizing bacteria at varying inorganic carbon concentrations by coupling the catabolic and anabolic processes

Several mathematical models have been proposed to describe nitrous oxide (NO) production by ammonia oxidizing bacteria (AOB) under varying operational conditions. However, none of these NO models are able to capture NO dynamics caused by the variation of inorganic carbon (IC) concentration, which has recently been demonstrated to be a significant factor influencing NO production by AOB. In this work, a mathematical model that describes the effect of IC on NO production by AOB is developed and experimentally validated. The IC effect is considered by explicitly including the AOB anabolic process in the model, which is coupled to the catabolic process with the use of the Adenosine triphosphate (ATP) and Adenosine diphosphate (ADP) pools. The calibration and validation of the model were conducted using experimental data obtained with two independent cultures, including a full nitrification culture and a partial nitritation culture. The model satisfactorily describes the NO data from both systems at varying IC concentrations. This new model enhances our ability to predict NO production by AOB in wastewater treatment systems under varying IC conditions