In order to enhance the performance of the nitrogen removal facilities treating livestock wastewater in Japan, optimization is often required. However, the improvement strategy to follow can be unclear, since the design and operational conditions applied in these facilities are not always the same. Thus, we studied the application of an ASM to simulate the performance of a livestock wastewater treatment system to predict the nitrogen removal efficiency under various conditions. A lab-scale reactor set up was operated under different dissolved oxygen and temperature conditions. Using data obtained through experiments, the model was evaluated.