Model-based optimization of a sequencing batch reactor for advanced biological wastewater treatment

Abstract

Sequencing batch reactor (SBR) technology for nutrient removal has received great attention from the wastewater treatment community [1-2]. A SBR process has a unique cyclic batch operation for biological wastewater treatment. Most of the advantages of SBR processes may be attributed to their single-tank designs and the flexibility allowing them to meet many different treatment objectives [3-5]. Due to the ever-stricter demands on effluent discharge quality, an existing SBR plant may require optimization in terms of nutrient removal, but this often needs a better understanding and quantification of the biological processes occurring in each phase of the SBR operation. A calibrated activated sludge model is a practical tool to try numerous operating scenarios within a short evaluation time when an upgrade of the SBR is considered. In this study, Activated Sludge Model No. 2d (ASM2d) is employed to model a lab-scale SBR [6]. Then, based on a survey of the relevant literature and a preliminary model-based analysis of the system [1,7], the following degrees of freedoms were identified and used for the SBR optimization: oxygen set-point in the aerobic phase (SO) and the lengths of anaerobic (TAN), aerobic (TA), and feeding (TF) phases. A grid of scenarios is formulated as full-factorial experimental design to simulate the effect of the key degrees of freedom in the SBR system. Effluent quality in combination with a robustness index for each of the scenarios is used to select the best operational strategy for the SBR system.