Performance evaluation and model-based optimization of the mainstream deammonification in an integrated fixed-film activated sludge reactor

[Display omitted] •Mainstream pilot-scale deammonification was simulated under seasonal temperature.•Intermittent aeration strategy plays an important role in stable NOB suppression.•The aeration was set to the optimized values (DO = 0.2 mgO2/L, on/off ratio = 0.05).•The nitrogen removal efficiency can enhance from 30% to > 50% (at optimized values).•The nitrogen removal rate increased up to 25 gN/m3d by optimized aeration values. This study aimed to model and optimize mainstream deammonification in an integrated fixed-film activated sludge (IFAS) pilot plant under natural seasonal temperature variations. The effect of gradually decreasing temperature on the performance was evaluated during a winter season and a transition period to summer conditions, and the correlation of the performance parameters was investigated using principal component analysis (PCA). The optimization of intermittent aeration in the long-term (30 days) dynamic conditions with on/off ratio and dissolved oxygen (DO) set-point control was used to maximize the N-removal rate (NRR) and N-removal efficiency (NRE). Optimization results (DO set-point of 0.2–0.25 mgO2/L, and on/off ratio of 0.05) increased the NRE and NRR of total inorganic N (daily average) from 30% to > 50% and 15 gN/m3d to 25 gN/m3d, respectively. This novel long-term optimization strategy is a powerful tool for enhancing the efficiency in mainstream deammonification.