Modeling complete and shortcut simultaneous nitrification and denitrification coupled to phosphorus removal in moving bed biofilm reactors

This study aimed to model simultaneous nitrification and denitrification (SND) and shortcut (partial) SND processes coupled to phosphorus removal in lab-scale moving bed biofilm reactors based on data collected during two different experimental campaigns. Modeling was performed using BioWin 6.0 to accurately predict the experimental results. A sensitivity analysis conducted for the first experimental campaign identified the most influential process parameters. The absolute variance, Thiel's inequality coefficient, and normal objective function were used to evaluate the consistency of the experimental and modeled data. The calibrated and validated models satisfactorily reproduced the experimental data for all experimental campaigns and within the acceptance criteria, resulting in a suitable tool for predicting the process efficiency. Moreover, calibrated and validated data were used to test different dissolved oxygen (DO) ranges (0.6–0.8 mg O2·L−1), pH (6.5–9.0), and hydraulic retention time (HRT) (0.5–1.0 d) to improve shortcut SND. Based on the different simulated scenarios, the intermittent DO conditions can induce and maintain the inhibition of the nitrite-oxidizing bacteria with an average N-NO3− concentration of 0.05 mg N·L−1, while an HRT of 0.9 d resulted in average effluent N-NH4+, N-NO3− and N-NO2− concentrations of 4.0, 0.02 and 0.07 mg·L−1, respectively, indicating an efficient shortcut SND process.