Comprehensive review of constructed wetlands implemented with advanced biotechnologies for carbon-neutral treatment of urban wastewater: Enhanced removal of nitrogen and reduction of greenhouse gas emissions

With rising urban population and urbanization, discharge of domestic wastewater increased dramatically. Centrally operated wastewater treatment plants (WWTPs) are being pressed for energy conservation and carbon footprint minimization, specifically in generating and emitting greenhouse gases (GHG) such as nitrous oxide (N 2 O). Constructed wetlands (CWs) as a new ecological wastewater treatment biotechnology have been receiving much attention in recent years for effective pollutants removal, cost savings, and landscape values. This study explores the potential for lower GHG emissions and better performance of pollutants removal in urban wastewater treatment using CWs. Integration of CWs and advanced biological nitrogen removal processes such as sulfur-based autotrophic denitrification (SAD), pyrite-based autotrophic denitrification (PAD) and anaerobic ammonium oxidation (anammox) is proposed as a lower GHG-emitting method. This study offers novel perspectives on carbon-neutral treatment of urban wastewater and contributes new insights towards low-carbon and sustainable development and stewardship at larger dimensions.