ABSTRACT
229Biological phosphate removal has been discovered in wastewater treatment plants by accident, and has developed from an interesting observation to an established biotechnological process implemented widely at full-scale. Presently, biological phosphorus removal models are developed sufficiently to be successfully applied for the description of activated sludge processes. The combined COD and N module of the activated sludge model no. 2 (ASM2) and the Delft BPR model proved well capable of describing the performance of a full-scale treatment plant in Haarlem. The next step should be the application of this model using also dynamic plant data, since all simulations described in this thesis were performed with static, steady-state, data. Furthermore, the model capability to predict well start-up conditions should be investigated. This research showed that modeling of wastewater treatment plants does not only bring more experience from practical application of the model, but also provides better understanding of plant operation and treatment processes and gives the opportunity to find out where the model should be improved. Additionally, it was demonstrated that the activated sludge models can be used for process design as well as for the optimization of performance of wastewater treatment installations. Following the rapid development of the activated sludge models, it can be expected that within few years the ASM4 may appear to describe COD, N and P removal for aerobic and anoxic conditions, possibly based on combination of ASM3 and a modified Delft BPR model. At that stage of model development it may be reasonable to let the model be applied and tested for a certain number of years (as was the case with ASM 1) prior to any further serious changes in the model tafke place.
