Real-Time Dynamic Control of Nitrification and Denitrification in an Intermittently Aerated Activated Sludge System for Enhanced Nitrogen Removal and Energy Efficiency

Advanced control systems have been recently implemented in wastewater treatment plants (WWTPs) to optimize activated sludge processes and reduce operational costs. Real-time dynamic control of ammonium-N and nitrate-N concentrations is important for the optimization of biological nitrogen removal (BNR) processes. This study pre-sents an advanced control strategy based on continuous monitoring of ammonium-N and nitrate-N concentrations to enhance nitrogen removal performance. Specifically, performance parameters were optimized using an automated controller set in an in-termittently aerated and fed activated sludge (IAF-AS) system treating domestic wastewater under two distinct operating scenarios: (i) constant ammonium-N loading rate (ALR) and (ii) sudden increase in ALR. In both scenarios, optimal durations of ni-trification and denitrification phases were dynamically determined. In the first sce-nario, under constant ALR of 0.2 g L⁻¹ d⁻¹, the controller maintained nitrification and denitrification durations below 30 minutes, achieving complete nitrogen removal. In the second scenario, when ALR exceeded 0.3 g L⁻¹ d⁻¹, the controller dynamically ex-tended these phases (> 60 minutes) to meet the effluent setpoints of 2 mg L⁻¹ ammo-nium-N and 1 mg L⁻¹ nitrate-N. Results demonstrate that real-time dynamic control enables maximized nitrogen removal efficiency by applying minimal necessary nitri-fication and denitrification durations, thereby reducing aeration energy demands and operational costs.