Achieving carbon neutrality in Shanghai's municipal wastewater treatment sector requires coordinated water conservation and technical improvement

Municipal wastewater treatment plants (WWTPs) situated within urban landscapes play a critical role in fostering sustainable urban development while concurrently serving as substantial contributors to greenhouse gas (GHG) emissions. Under the dual pressure of future urban socioeconomic development and the carbon neutrality target, it is important to identify GHG emission reduction pathways for municipal WWTPs. Existing research on GHG emission reduction in WWTPs exhibit a notable absence of a comprehensive city-centric perspective, with insufficient consideration given to the impact of water conservation measures. We constructed a GHG emission accounting system for the municipal WWTPs employing Shanghai as a case study. Based on field surveys of typical WWTPs, we proposed GHG emission reduction pathways and future demandtechnology scenarios. Our results showed that, with the robust mitigation measures, Shanghai's municipal WWTPs have the potential to curtail GHG emissions to 0.55 Mt by 2050. Notably, GHG emission reduction can be achieved through water conservation and technical improvement. Medication optimization and energy saving are significant mitigation measures for GHG emission reduction, and should be optimally considered in the future. This investigation not only establishes a forward-looking GHG emission reduction roadmap for the municipal WWTPs at the city-scale but also imparts valuable insights to urban management practices in analogous urban settings.