title: Evaluation of the potential for operating carbon neutral WWTPs in China.
abstract: Carbon neutrality is starting to become a hot topic for wastewater treatment plants (WWTPs) all over the world, and carbon neutral operations have emerged in some WWTPs. Although China is still struggling to control its water pollution, carbon neutrality will definitely become a top priority for WWTPs in the near future. In this review, the potential for operating carbon neutral WWTPs in China is technically evaluated. Based on the A(2)/O process of a typical municipal WWTP, an evaluation model is first configured, which couples the COD/nutrient removals (mass balance) with the energy consumption/recovery (energy balance). This model is then applied to evaluate the potential of the organic (COD) energy with regards to carbon neutrality. The model's calculations reveal that anaerobic digestion of excess sludge can only provide some 50% of the total amount of energy consumption. Water source heat pumps (WSHP) can effectively convert the thermal energy contained in wastewater to heat WWTPs and neighbourhood buildings, which can supply a net electrical equivalency of 0.26 kWh when 1 m(3) of the effluent is cooled down by 1 °C. Photovoltaic (PV) technology can generate a limited amount of electricity, barely 10% of the total energy consumption. Moreover, the complexity of installing solar panels on top of tanks makes PV technology almost not worth the effort. Overall, therefore, organic and thermal energy sources can effectively supply enough electrical equivalency for China to approach to its target with regards to carbon neutral operations.
authors.affiliation: Key Laboratory of Urban Stormwater System and Water Environment/R&D Centre for Sustainable Wastewater Treatment (Beijing University of Civil Engineering and Architecture), Ministry of Education, Beijing 100044, PR China. Electronic address: xdhao@hotmail.com.
authors.forename: Xiaodi
authors.initials: X
authors.lastname: Hao
authors.affiliation: Key Laboratory of Urban Stormwater System and Water Environment/R&D Centre for Sustainable Wastewater Treatment (Beijing University of Civil Engineering and Architecture), Ministry of Education, Beijing 100044, PR China.
authors.forename: Ranbin
authors.initials: R
authors.lastname: Liu
authors.affiliation: Key Laboratory of Urban Stormwater System and Water Environment/R&D Centre for Sustainable Wastewater Treatment (Beijing University of Civil Engineering and Architecture), Ministry of Education, Beijing 100044, PR China.
authors.forename: Xin
authors.initials: X
authors.lastname: Huang
mesh_terms: D002244:Carbon / Q000032:analysis*; D002681:China; D008962:Models, Theoretical; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D002244:Carbon
keywords: Anaerobic digestion; Carbon neutrality; Organic energy; Photovoltaic (PV) technology; Wastewater treatment plants (WWTPs); Water source heat pumps (WSHP)