Evaluation of Greenhouse Gas Emissions and Sludge Characteristics in Typical AAO Process WWTPs in Taihu Lake Basin, China

This study investigated sludge characteristics and greenhouse gas (GHG) emission from 16 anaerobic‐anoxic‐oxic (AAO) process wastewater treatment plants (WWTPs), 11 municipal and 5 industrial WWTPs, located in the Taihu Lake Basin, China. Influent/effluent water quality, sludge properties, operational parameters, GHG emission patterns, and their influencing factors were systematically analyzed. Results revealed significant differences in emission profiles between municipal and industrial WWTPs: Although electricity consumption dominated emission in both types, the sludge treatment and disposal stage contributed notably (40.1%) to industrial WWTP emission. Comparative analysis showed industrial WWTPs had significantly higher unit emission during wastewater treatment than municipal counterparts ( p ≤ 0.01), whereas municipal WWTPs exhibited significantly higher emission intensity from chemical consumption ( p ≤ 0.05). Distinct regional variations in emission intensity and distribution were observed among WWTPs in Suzhou, Wuxi, and Changzhou, reflecting differences in operational and management priorities. Correlation analysis further identified electricity consumption as the primary driver of total emission intensity ( p ≤ 0.001), with effluent total nitrogen (TN) negatively correlated and effluent chemical oxygen demand (COD) positively correlated with emission intensity. Additionally, sludge calorific value and organic matter content were significantly negatively correlated with net emissions from sludge treatment. These findings highlight the need for differentiated GHG mitigation strategies tailored to WWTP type and region, emphasizing optimization of aeration energy consumption, improvement of sludge dewatering processes, and enhancement of sludge calorific value and energy recovery to achieve low‐carbon operation of AAO processes.