Abstract

Mathematical models and simulation are becoming increasingly used tools in the optimization of wastewater treatment plants. In this paper, the use of these tools is presented for wastewater treatment plant upgrading. Two case studies are presented, which will be upgraded for tertiary treatment to achieve effluent total nitrogen and total phosphorous concentrations below 10 mg/l and 1 mg/l, respectively. The plant performance after upgrading was assessed by first designing the process model, before upgrading the model for future operation under dynamic influent conditions. Long-term simulations revealed some bottlenecks in the upgraded plant performance and thus helped to improve the plant designs. In one case the total volume of the reactors was increased subsequently, while in the other case tighter denitrification control or additional reject water treatment was proposed. These results indicate that mathematical models can be considered as valuable tools to complement the established wastewater treatment plant design procedures. Advantages are gained by simulating the operation under dynamic operating conditions, precise wastewater characterization, as well as adjustment of stoichiometric and kinetic parameters to a particular wastewater treatment plant operation.