Ammonia-based aeration control with optimal SRT control: improved performance and lower energy consumption

• Published in: Water science and technology 2019-01, Vol.79 (1), p.63-72
• Main Authors: Schraa, Oliver, Rieger, Leiv, Alex, Jens, Miletić, Ivan
• Format: Article
• Language: English
• Subjects: Activated sludge; Activated sludge process; Aeration; Ammonia; Ammonia - analysis; Ammonia - chemistry; Automation; Bioreactors; Cascade control; Chemical oxygen demand; Conservation of Water Resources - methods; Control; Control algorithms; Controllers; Dissolved oxygen; Effluents; Energy; Energy conservation; Energy consumption; Hydraulics; Microorganisms; Nitrification; Nitrogen; Nutrient removal; Oxygen; Process controls; Resource recovery; Retention time; Seasonal variations; Sewage; Sludge; Solid suspensions; Suspended particulate matter; Suspended solids; Waste Disposal, Fluid - methods; Water resources; Water Supply - statistics & numerical data; Water treatment
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2019.032

Ammonia-based aeration control (ABAC) is a cascade control concept for controlling total ammonia nitrogen (NH -N) in the activated sludge process. Its main goals are to tailor the aeration intensity to the NH -N loading and to maintain consistent nitrification, to meet effluent limits but minimize energy consumption. One limitation to ABAC is that the solids retention time (SRT) control strategy used at a water resource recovery facility (WRRF) may not be consistent with the goals of ABAC. ABAC-SRT control is a strategy for aligning the goals of ammonia-based aeration control and SRT control. A supervisory controller is used to ensure that the SRT is always optimal for ABAC. The methodology has the potential to reduce aeration energy consumption by over 30% as compared to traditional dissolved oxygen (DO) control. Practical implementation aspects are highlighted for implementation at full scale, such as proper selection of the set point for the supervisory controller, proper calculation of the rate of change in sludge inventory, using a mixed liquor suspended solids (MLSS) controller, and tuning of the controllers. In conclusion, ABAC-SRT is a promising approach for coordinated control of SRT, total ammonia nitrogen, and dissolved oxygen in the activated sludge process that balances both treatment performance and energy savings.