Under the umbrella of the N2Oara project at Eawag, researchers conducted 14 long-term observation series on various types of treatment plants in Switzerland. This enabled them to produce a broad data set for WTP emissions, and pave the way for a deeper understanding of emissions drivers. The results of the research project were recently presented. in the journal AQUA & GAS. Emissions of N2O from biological wastewater treatment make up the greatest proportion of greenhouse gas emissions from the treatment process as a whole. Biological treatment centres around the processes of nitrification and denitrification. The findings show that, if these process steps could be optimised, overall greenhouse gas emissions from a WTP could be reduced by up to 75 per cent.
Nitrous oxide emissions from wastewater treatment plants have long been underestimated.”
Wenzel Gruber, Eawag
No impact on the quality of treated wastewater
According to the researchers, optimisation could be achieved by boosting nitrogen elimination and preventing the accumulation of nitrite. “As our study shows, it’s possible to achieve a huge reduction in N2O emissions without reducing the quality of the treated water,” explains Gruber. In fact, the measures described here actually improved the effluent quality. However, before robust optimisation measures can be recommended, there is a need for greater insights into the mechanisms involved – and it is with this objective in mind that Eawag has launched two new projects. Eawag has been addressing the production of nitrous oxide in WTPs for a long time: the first dissertation on N2O from WTPs was authored in 1996 and was followed by another doctoral thesis in 2013. Nitrous oxide research was then presented to a wider audience at the Info Day 2018 on Wastewater as a Resource.