Optimizing reaction configurations of sequential batch reactor (SBR) for nitrogen removal from wastewater

Biological nutrient removal in SBRs requires the optimized sequencing of aerobic and anoxic phases to balance nitrification, denitrification and energy use. This study uses GPS-X v8.1 to simulate a 212 m 3 SBR treating synthetic domestic wastewater (COD 2,500–3,500 mg L −1 ; TN ≈ 60 mg N L −1 ) under a 24-h cycle (1 h fill, 20 h react, 2 h settle/decant, 1 h idle) with DO setpoint of 2.0 mgL −1 . Eleven operational strategies—including pre-anoxic, post-anoxic, intermittent aeration and their combinations—were evaluated. The model was calibrated and validated against independent plant data (R 2 ≥ 0.85; NSE ≥ 0.70). A combined pre-anoxic + post-anoxic + intermittent aeration configuration delivered the best trade-off, achieving 87.1% TN removal and 88.6% TP removal while maintaining BOD and COD removal >89% and a moderate energy penalty. Sensitivity and multi-objective optimization (TN removal vs energy) identified SRT, internal recirculation ratio and aerobic fraction as dominant controls and produced Pareto-optimal aeration schedules for practical implementation. These results provide actionable guidance for energy-efficient SBR operation to meet stringent nutrient targets. • Calibrated an ASM-based SBR model with full parameter transparency and bootstrapped confidence intervals. • Validated predictions for NH 3 –N, TN, TP, and COD against an independent dataset (R 2 ≥ 0.85). • Conducted global sensitivity and uncertainty analyses to rank parameter influence and derive 95% prediction bands. • Verified mass-balance closure (< 3% error) and decanting-flow fits with quantitative goodness-of-fit metrics. • Identified Pareto-optimal aeration schedules that balance total nitrogen removal and energy consumption.