Significant changes in operational conditions have impacted the environmental performance of sewage treatment plants. This study employed a life cycle assessmentLife Cycle Assessment (LCA) to compare the environmental impacts of a Xiamen sewage treatment plant during 2022 and 2024, focusing on its sewage treatment phase. Using SimaProSimaPro software with the ReCiPe 2016 Midpoint method and defining the treatment of 1 cubic meter of sewage as the functional unit, key parameters including greenhouse gasGreenhouse gases emissions, energy consumption, and chemical usage were quantified. The 2022 emission profile identified direct greenhouse gasGreenhouse gases releases, specifically methane and nitrous oxide, as the dominant climate forcing agents, accounting for 4.26 kg CO2-equivalent (CO2eq) per functional unit. Secondary contributions arose from grid electricity consumption (0.381 kg CO2eq), reflecting energy-intensive operational processes. By 2024, improvements in operational efficiency and the restoration of maintenance protocols reduced direct gas emission-related carbon emissions to 3.85 kg CO2eq. Increased disinfectant use and microplastic presence during the study period were found to inhibit microbial activity, thereby exacerbating energy demands. The study highlights that optimizing direct emission management, enhancing energy efficiency, and strengthening equipment maintenance are critical strategies for mitigating environmental impacts. Integrating renewable energy, refining treatment processes, and addressing emerging pollutants are essential for promoting sustainable development in the sewage treatment industry. These findings provide theoretical and practical insights for low-carbon operation and environmental risk management amid operational changes and recovery.