The impact of rising temperatures on wastewater treatment plants’ energy use and carbon emissions in China: A climate feedback perspective

Wastewater treatment plants (WWTPs) contribute significantly to global warming via greenhouse gas (GHG) emissions. Previous studies have focused on quantifying the GHG emissions of WWTPs and identifying mitigation solutions, but it is unclear how global warming might in turn affect WWTPs, especially on a large scale. In this study, we compiled data from thousands of plants across China and analyzed the relationships between plant electricity consumption and key climate variables. We find that WWTPs in relatively cold and hot climates are vulnerable to temperature increase and are expected to experience substantial increase electricity use. On the national scale, global warming is projected to increase WWTP's annual electricity consumption by 17 % under RCP4.5, and by 44 % under RCP8.5 or 2.8 times as much. The disparity between the two climate scenarios would be amplified to 3.6 times for electricity-related GHG emissions, because RCP 8.5 embodies a more carbon-intensive energy structure. GHG emissions of WWTPs electricity consumption would increase by 37.82 % (11.43-71.94 %) by 2090s above 2006 levels under RCP 8.5, and by 10.46 % (0.89-23.56 %) under RCP 4.5. These results suggest that global warming can aggravate the GHG impact of WWTPs: the worse the warming, the stronger the climate-WWTP feedback effect, underscoring the importance and urgency of accelerating the transition to a clean energy future. Furthermore, WWTPs in cold and hot climates should be prioritized for adaptation to increase resilience against temperature rise and fluctuation.