Four years of on-line gaseous N2O emission monitoring at a large WWTP - lessons learned and mitigation strategy outline

The largest potential for decreasing the greenhouse gas emissions during wastewater treatment is related to controlling the emissions of nitrous oxide, N2O. The Viikinmäki WWTP situated underground has collected a comprehensive history data of N2O emissions together with other related process parameters. This data were analysed, but despite the long-span monitoring, there are still periods of higher emissions which are not correlated with any process parameter. This confirms the results from other shorter term studies and emphasizes the need for further research in order to fully understand the complexity of processes leading to N2O emissions. Moreover, in this work the effect of different operational strategies on the production and emission of N2O at the Viikinmaki WWTP were investigated and evaluated by applying dynamic process modelling.