Improving the design of a full scale wastewater treatment plant with use of the complex activated sludge model

This thesis discusses the application of a complex activated sludge modelling tool which was implemented to assure the predictability and improve the design and effectiveness of a biological wastewater treatment for the full-scale Wastewater Treatment Plant (WWTP) “Porec South”, situated in the touristic coastal town of Porec (Parenzo) - Republic of Croatia. The above mentioned plant represents a part of a larger project consisting of four wastewater treatment plants, all designed with the Membrane Bioreactor Technology (MBR). This project has been awarded to a consortium of companies SUEZ-STRABAG in August 2015, for which the Design & Build process is still ongoing during the development of this work. The selected tool used for the simulation is BioWin 5.0 (EnviroSim Associates Ltd.). Since the plant is characterized by a large seasonal difference in terms of its hydraulic and mass loads, the model was applied for the period with the heaviest load (summer) and then the simulation was repeated for the period with the lowest load (winter). The obtained study and simulations describe and confirm the chosen configuration of the WWTP Porec South and its design using a modelling tool which is widely used and universally recognized in the scientific community. The results will permit to check and validate the design and to confirm process tank volumes (anaerobic, anoxic and aerated volumes), sludge concentration, excess sludge extraction and sludge age, recirculation rates and most importantly, the compliance to the discharge limits and the requirements of the project . Furthermore, an additional simulation is performed to demonstrate the effect of an extreme peak flow event (5-day storm event) on the plant and how it might affect the performance of the wastewater treatment process. This would give further performance indicators of the project, thus assuring the safety and operability of the plant.