Oxygen Penetration Depth as a Tool to Predict Nitrous Oxide Emissions from Granular Partial Nitritation Wastewater Treatment Systems

Six Nitrous Oxide (N2 O) emission tests, corresponding to combinations of three dissolved oxygen and two temperature levels, were performed on a lab-scale granular Partial Nitritation (PN) reactor. Emission factors (EFN2O ) ranged from 0.60 to 2.97 % of the Ammonium Oxidation Rate, and were negatively correlated with the granules’ estimated oxygen penetration depths (δO2 ). The ratio between anoxic and aerobic granule volume, easily derivable from δO2 , was linearly correlated with EFN2O (R2 =0.91), and was therefore proposed as a tool to predict N2 O emissions from PN granules. This study lays the foundations for future works aimed at refining the proposed EFN2O prediction method.