Geographic distribution of net-zero energy wastewater treatment in China

Abstract In China, significant differences in climatic conditions, economic development levels, treatment processes used, and population density inevitably lead to regional patterns in the energy recovery and consumption of wastewater treatment plants (WWTPs). However, research is still lacking on characteristics of WWTPs in different regions and how potential patterns affect the energy self-sufficiency of WWTPs in China. In this study, the geographic distribution of the energy self-sufficiency of municipal wastewater treatment in China is investigated based on a net-zero energy (NZE) model. The results indicated that only 19% of the investigated WWTPs could generate enough energy to offset their energy consumption under their existing operating conditions. The maximum self-sufficiency rate was 186.43% among all of the investigated WWTPs in eastern China. Therefore, their current wastewater treatment operation strategies are not conducive to energy recovery. However, 30% of the investigated WWTPs could realize 100% energy self-sufficiency by adjusting their metabolic substrate allocation. There is a higher probability of achieving the NZE status in eastern and northeastern China due to more effective operations, higher chemical oxygen demand (COD) removals, and higher economic levels. A higher energy consumption and worse energy recovery performance lead to a low probability of achieving NZE in western China. However, in western China, there is a great potential for improving the energy self-sufficiency of the WWTPs by regulating their metabolic material allocations. These findings provide a nationwide perspective on energy-saving and emission reduction measures for WWTPs and facilitate the attainment of energy neutralization in the WWTPs in China.