Modelling Greenhouse Gas Emissions of a Hybrid Fixed-film Anammox Process Treating Sludge Dewatering Centrate in Wastewater Treatment

The aim of this study is to estimate and optimize greenhouse gas (GHG) emissions of a process in wastewater treatment, which utilizes anaerobic ammonium oxidation (Anammox). The single-stage nitritation-Anammox process applies fixed biofilm carriers and treats the centrate of sludge dewatering. GPS-X biokinetic modelling tool was used for quantifying the specific nitrous oxide, carbon dioxide and methane emissions at various operational conditions. In general, the amount of biology related GHG production was estimated to be higher than that of indirect emissions, by three orders of magnitude. Of direct emissions, nitrous oxide gas production should be taken into account primarily. Based on the simulations, feasible options of minimising N2O emissions include applying an operational temperature of 30-35°C, and increasing airflow to reduce the effect of oxygen limitation. To release less N2O, the process should also preferably be operated as an IFAS application with a low concentration of suspended solids (1.5-2 g/L), or even without sludge recycle.