Theoretical and practical aspects of modelling activated sludge processes

This thesis describes the full-scale validation and calibration of a integrated metabolic activated sludge model for biological phosphorus removal. In chapters 1 and 2 the metabolic model is described, in chapters 3 to 6 the model is tested and in chapters 7 and 8 the model is put into practice. Chapter 1 is a general introduction to this research. Chapter 2 is a more specific introduction to the metabolic biological phosphorus removal (BioP) model. The goal of this introduction is to obtain a better understanding of the stoichiometric and kinetic structure of the metabolic model and the role of the storage polymers glycogen, poly-phosphate and PHB. In chapters 3 and 4, the model is validated at full-scale conditions. Chapter 3 describes the simulation of a full-scale nutrient removing WWTP at steady state conditions. In chapter 4, the start-up of a full-scale WWTP is simulated. Under start-up conditions model kinetics can be tested more extensively than is possible at steady state conditions. In chapter 5, a method presented for data evaluation, reconciliation and model calibration. The method is tested in a full-scale simulation study. In chapter 6, all previous modelling experiences with the metabolic BioP model are evaluated. The adapted model is tested on the basis of several lab-scale experiments. The updated version of the integrated model is presented in appendix III. In chapters 7 and 8, the model is put into practice. In a case study, a process control based on the oxidation reduction potential was evaluated. On the basis of a literature study, in chapter 7 the physical meaning of measuring the oxidation reduction potential in activated sludge is discussed. In chapter 8, it is demonstrated how the model can be used for (ORP related) process control and control design