Optimization of a sequencing batch reactor for biological nitrogen removal

The nitrification step of a biological nitrogen removal process conducted in a sequencing batch reactor (SBR) was studied. The process is time oriented and history-dependent: changes in the length of fill and react phases alter process productivity. Due to process complexity, heuristic optimization is rarely efficient, and a model-based approach is often necessary. In the present work, IAWQ No. 1 Model (Henze, M., Grady, C. P. L, Gujer, W., Marais, G. V. R. and Matsuo T. (1987). A general model for single-sludge wastewater treatment systems. Water Research, 21(5), 505–515), originally developed for activated sludge processes, was adapted to SBR, and batch scheduling and filling strategy was sought with a constrained successive quadratic programming (SQP) algorithm. Productivity results favored a discrete fill strategy, consisting of symmetric pulses for wastewater and oxygen supply to the system. Optimal conditions were imposed on an instrumented bench scale SBR and a significant reduction in batch time was achieved, using a symmetric pulse strategy for wastewater and oxygen addition.