Monitoring the Emissions of non-CO2 Greenhouse Gases from Wastewater Treatment Plants

The wastewater sector contributes significantly to Sweden's total greenhouse gas emissions, and with continued population growth, the impact of municipal wastewater treatment plants will increase even further. Therefore, the connection between operating parameters and direct methane and nitrous oxide emissions from aerated and non-aerated bio basins has been investigated in this work. The gas concentrations were measured by applying the closed flux chamber method in combination with a Fourier Transform Infrared multigas analyzer (GT 5000 Terra) at Kungsängen’s wastewater treatment plant in Västerås. The most relevant operating parameters were chosen by the empirical Pearson correlation coefficients with data from the actual measurements and were further examined within a linear regression model. Based on the results of the model, an attempt was made to extend the findings from the measurement to a prediction of emissions for the entire year 2024. The results of the regression model showed that approximately and were generated from the aerated basins in 2024. As temperature occurred to have a significant influence on the CH4 emissions from the regression model, the linear regression was repeated without considering the temperature, which led to . Furthermore, the annual emissions of Kungsängen’s wastewater treatment plant were determined again by using the Tier 1 estimation approach of IPCC leading to ranges from to as well as from to . In comparison with the results from the linear regression model, it showed that nitrous oxide emissions lie within this range. However, there are several reasons for 2024’s CH4 emissions to be out of that range. Based on these findings and further measurements to be carried out in the future, a more reliable and accurate approach to estimating or predicting emissions can be developed than the IPCC approach.