Carbon Emission Characteristics and Low-Carbon Operation Evaluation of Some Wastewater Treatment Plants in East China: An Empirical Study Based on Actual Production Data

Against the backdrop of China’s “dual carbon” strategy, investigating the carbon emission characteristics and low-carbon operational status of wastewater treatment plants (WWTPs) across regions is pivotal for achieving synergistic pollution reduction and carbon mitigation. Leveraging 2024 operational data from 98 WWTPs in eastern China—encompassing treatment volume, energy consumption, sludge production, and chemical dosages—this study refined the Assessment Standard for Carbon Mitigation in Municipal WWTPs and Technical Specification for Low-Carbon Operation of WWTPs. A novel carbon accounting framework and low-carbon performance evaluation system were subsequently developed to analyze the impacts of treatment scale, technological configuration, and load rate on carbon footprints. Key findings revealed an average carbon intensity of 0.399 kg CO2-eq/m3 for the region, with small-scale facilities (0.582 kg CO2-eq/m3) exhibiting significantly higher emissions compared to their large-scale counterparts (0.392 kg CO2-eq/m3). Indirect emissions constituted 62.1% of the total footprint, while chemical dosing contributed 14.2%, primarily driven by carbon sources and phosphorus removal agents. Fossil-derived CO2 accounted for 4.6% of emissions. Notably, the AAO process demonstrated the lowest carbon intensity (0.370 kg CO2-eq/m3), whereas SBR systems registered the highest (0.617 kg CO2-eq/m3). Furthermore, 25% of the assessed facilities were classified as high-emission plants. Strategic recommendations are proposed, including prioritizing AAO process optimization, implementing intelligent chemical dosing control, utilizing food wastewater as an alternative carbon source, and enhancing operational load rates, to advance synergistic environmental and carbon mitigation goals in eastern China’s wastewater sector.