Improved model of secondary clarifier in A 2 /O process

The complex behavior of the secondary clarifier and its great importance in the successful operation of the activated sludge process (ASP) have made the settling process a major issue for researchers working in the field of mathematical modeling. So, a precise model of the secondary clarifier can describe the actual behavior of a sewage plant better. But in ASM2, the solid/liquid separation in a secondary clarifier, which is highly nonlinear, is not considered. The solid/liquid separation affects not only the biological reaction but also the quality of the effluent. In this paper an improved secondary clarifier model based on a one‐dimensional settler model is established in terms of the solid flux concept and a mass balance. Through some given assumptions, a model of A 2 /O process including secondary clarifier is built, and then simulated. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.