LAUSR

Abstract In the last decade, policies exclusively based on reducing the electricity consumption have pushed for the use of more energy efficient processes, such as anammox-based processes for biological nitrogen removal from wastewater. In this study, a pilot-scale Anammox reactor has been incorporated into an optimized full-scale wastewater treatment plant. The supernatant of the reject sludge waters has been treated by the full scale wastewater treatment plant with and without incorporating a full-scale Anammox reactor in the sludge line. Energy consumption and nitrous oxide emissions have been monitored in both scenarios. In terms of total impact, a side-stream Anammox process can effectively mitigate the nitrogen rich sludge reject water. The impact on the carbon footprint of the full-scale wastewater treatment plant is instead, to its best, neutral. The risks related to the incorporation of an Anammox process have been highlighted: if operations are not bound to good practices, they may lead to a severe increase in carbon footprint. The use of side-stream technologies, that can further reduce both electricity consumption and the total impact but not the carbon footprint, remains attractive only when good practices for nitrous oxide mitigation are enforced.