This report is only available in Swedish. English summary is available in the report.
At Slottshagen wastewater treatment plant (WWTP), one of the first mappings of nitrous oxide (N2O) emissions from the reject water treatment was performed. The first measurements were carried out in 2012 and showed relatively high emissions of nitrous oxide with emissions corresponding to an average of 10 % of the incoming nitrogen load but periodically significantly higher emissions than that. Thus, it was concluded that the process, despite efficient nitrogen removal, contributed to a significant environmental impact. To reduce the negative environmental impact caused by the high emissions of nitrous oxide, which is a 298-fold stronger greenhouse gas than carbon dioxide, IVL developed various action strategies for Nodra AB that would result in reduced emissions both in the short and long term. As a quick measure, an adaptation of the ethanol dosing strategy was recommended to reduce emissions. A monitoring measurement showed that nitrous oxide emissions had been reduced to an average of 5-6 % of the average nitrogen load. The long-term recommendation to Nodra AB was to change the treatment process from Sequential Batch Reactor (SBR) with conventional nitrification and denitrification to a 1-step deammonification, which includes the biological processes nitration and anammox. After completion of the reconstruction in 2017, a new measurement campaign was performed in 2018. These measurements indicate significantly lower nitrous oxide emissions in the deammonification process (<1 % of the nitrogen load). A further optimization of the process with a focus on pH control, which was carried out in collaboration with Mälardalen University (MDH) and Purac AB, resulted in even lower emissions of <0.2 % of the nitrogen load. Although in this specific case, certain mitigation strategies were proposed, there may be several other action strategies possible. The most important part of a successful reduction of greenhouse gas emissions is the knowledge of the current situation and the willingness to change a negative state. Nodra AB has been driving these questions and despite high emissions that were discovered during the mapping process, they have been continuously working to reduce these with the help of external expertise.
Report number: B2338
Authors: Christian Baresel, Niclas Bornold, Jing-Jing Yang, Linda Kanders, Magnus Eliasson Linda KandersDownload publication