Linking seasonal N2O emission pattern and nitrification failure to microbial population dynamics in a full-scale wastewater treatment plant

Seasonal NO2- accumulation and N2O emission episodes can be linked directly or indirectly to shifts in the activated sludge microbiome. Of interest for full scale operation are changes in the nitrogen converting populations resulting in reduced nitrification performance and potentially causing increased N2O production. We combined an extensive N2O measurement campaign over 1.5 years and 16S rRNA sequencing for microbial community analysis during two seasonal N2O emission episodes. This is the first study to discuss shifts in microbial community composition as a potential cause for seasonal N2O emission pattern and nitrite accumulation based on long-term data of a full scale WWTP.