With rapid urbanization and infrastructure investment, wastewater treatment
plants (WWTPs) in Chinese cities are putting increased pressure on energy consumption and
exacerbating greenhouse gas (GHG) emissions. A carbon footprint is provided as a tool
to quantify the life cycle GHG emissions and identify opportunities to reduce climate
change impacts. This study examined three mainstream wastewater treatment technologies:
Anaerobic–Anoxic–Oxic (A–A–O), Sequencing Batch Reactor (SBR) and Oxygen Ditch,
considering four different sludge treatment alternatives for small-to-medium-sized WWTPs.
Following the life cycle approach, process design data and emission factors were used by
the model to calculate the carbon footprint. Results found that direct emissions of CO2 and
N2O, and indirect emissions of electricity use, are significant contributors to the carbon
footprint. Although sludge anaerobic digestion and biogas recovery could significantly