Minimising greenhouse gas emissions from small and medium-sized wastewater treatment plants

Municipal wastewater treatment plants often use the activated sludge process in single-stage reactors with nitrification or in two-stage reactors with nitrification and denitrification. Both processes, if operated under unfavourable environmental conditions, can lead to excessive production of nitrous oxide (N2O), a gas with a high global warming potential (GWP) of about 300. In turn, the decomposition of organic pollutants leads to the release of CO2 and CH4 into the atmosphere. When analysing greenhouse gas emissions from wastewater treatment, it is also necessary to consider indirect emissions, mainly related to the use of energy from external sources. Estimating the magnitude of these emissions based on actual measurements is difficult. This article presents the results of simulation studies on the potential for reducing greenhouse gas emissions from small and medium-sized wastewater treatment plants with aerobic sludge digestion (AD) through operational optimisation of existing plants or the application of new technologies.