Centralized water and wastewater treatment are key components of modern society but, at the same time, sources of greenhouse gas emissions. In this study, we carried out an assessment of the role of centralized water and wastewater treatment as a greenhouse gas producer in Finland, based on the existing literature and a questionnaire study. The aim of the study was to outline the significance of the emissions, as well as to discover what the main sources of the emissions are. The possibility of improving energy efficiency and lowering the emissions were also assessed. Indirect emissions from, for example, the use of chemicals or the manufacture of assets could not be considered when making this preliminary survey. The results of the research indicate that water and wastewater utilities do not produce as much greenhouse gas in Finland as, for instance, the heating of water in private households. We estimated the annual emissions from the centralized water and wastewater sector to be approximately 320,000 t carbon dioxide equivalents. Emissions could be reduced through, for example, shifting to energy-efficient sludge treatment, such as anaerobic methods. We estimated that gaseous emissions resulting from wastewater treatment, wastewater sludge treatment, the discharge of treated effluent and sludge disposal in landfills form approximately 50% of total emissions.

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