The anaerobic-anoxic-aerobic (A2/O) process is a commonly used biological treatment technology for wastewater treatment. The process divides the treatment process into three stages: anaerobic, anoxic and aerobic. In the anaerobic stage, organic matter is partially degraded by microorganisms under anaerobic conditions. Then, under anoxic conditions, nitrogen is released and nitrification takes place. Finally, under aerobic conditions, the microorganisms further oxidize the organic matter and remove nitrogen and phosphate.The A2/O process is capable of efficiently removing organic matter, nitrogen and phosphorus, and is a mature technology widely used in municipal and industrial wastewater treatment, with high treatment efficiency and low energy consumption. When utilizing this dataset for Life Cycle Assessment (LCA), users should pay attention to the geographical specificity of the data as it only reflects the environmental performance of A2/O processes at WWTPs within China. The dataset should be used in consideration of the local water treatment infrastructure and regulations. Recalibration may be necessary when applying these data to different regions or scales of operation. Users should also account for any subsequent innovations or improvements in the A2/O process technology when interpreting the dataset.