Modeling and Simulation of the Activated Sludge Process at the Kalmar Wastewater Treatment Plant Using the Biowin Simulator

Sammanfattning

Wastewater is a major source of pollution of oceans, lakes, rivers, and groundwater. Treatment of wastewater to remove pollutants in wastewater treatment plants (WWTPs) is essential before the water is discharged into the recipients. Wastewater treatment plants are complex and sophisticated systems that must be controlled and monitored to ensure that the wastewater treatment process is working properly, and that the effluent fulfills the required discharge quality. In order to improve and optimize the treatment process, modelling treatment performance in response to changes in operation parameters, such as influent and temperature, would be a useful tool. The Biowin simulator is an example of software which can be used to simulate different types of wastewater treatment plants and processes, where simulation results can be later utilized to increase the understanding of how to manipulate operational parameters to improve performance and increase the efficiency of wastewater treatment plant and reduce the cost of energy consumption. Using Biowin, water chemistry, precipitation reactions, mass transfer, oxygen and other gas-liquid interactions can be modelled. In this study, Biowin was used to simulate the activated sludge process in Kalmar WWTP. The objectives were to simulate the nitrogen removal process in activated sludge treatment plants in Kalmar and to assess whether the simulation of different scenarios using Biowin results in reliable and accurate findings, that can be used for future design and planning. The hypothesis of the work is that Biowin is well suited for predicting nitrogen removal in Kalmar WWTP and that this simulation tool is suitable for this type of prediction. For Kalmar WWTP simulation, 2019 data (inflow, wastewater temperature, the wastewater components) were imported to the Biowin simulator. Based on the Kalmar WWTP process schematic, each section was configured in Biowin and the settings of each unit were adjusted. The simulation was run using data of January and February of 2019. The simulations were then calibrated to increase the fitness between the simulated and measured data. Then, a simulation was run again for the entire year 2019. Next, data from the first two months of 2022 were collected and imported into Biowin. The same settings and configurations as for 2019 simulations were used for the simulation of 2020 data, except that the oxidation basins were assumed to be flexible basins. Finally, both the simulated and measured data of ammonium, nitrate and total nitrogen in the effluent were compared to the measured data, and the fitness and validity of Biowin results were evaluated. The simulations were run for three temperatures: 7 °C, 13 °C and 18 °C for 2019 and the results were compared. The total nitrogen removal results show that Biowin was able to simulate data for nitrogen, ammonium, and nitrate that differed slightly from the measured data, with a slightly larger difference for nitrate. For three different effluent temperatures, 7 °C, 13 °C, and 18 °C, Biowin showed that nitrogen and ammonium removal performed better at a temperature of 18 °C. Total nitrate behaves differently than total nitrogen and ammonium and based on this study it would be difficult to say at which temperature nitrate removal works better. In conclusion, Biowin is a suitable tool for simulation of total nitrogen, based on this study, and its results can be used for future design or planning.