Municipal wastewater treatment plants (WWTPs) consume lots of energy and produce large amounts of greenhouse gases (GHGs) to remove pollutants. Nowadays, the concept of energy self-sufficient WWTPs is attracting more attention. This study aims at proposing an evaluation framework for energy neutrality potential of WWTPs from an integrated dimension of water-energy efficiency and energy recovery. To achieve this, operational data of 970 WWTP samples located in Yangtze River Economic Belt (YREB) was extracted from China Urban Drainage Yearbook 2018. The chemical and thermal energy of WWTPs samples were estimated via the technology of combined heat and power (CHP) and water source heat pump (WSHP), respectively. Based on the results of CHP and WSHP, 2 key performance indicators (KPIs) were established to characterize the capability of WWTPs from aspects of basic function and energy recovery, respectively. The first one is comprehensive water-energy efficiency (CWEE) solved by data envelopment analysis (DEA) and the other is energy self-sufficiency rate (ESSR). In terms of the result, 98 samples were determined to be the benchmark, while 112 have potential to achieve the full self-sufficiency level. Moreover, there are 4 types of energy neutrality potential classified with the median of two KPIs set as the critical value. Besides, the explanatory factors were also analyzed, and results show that treatment capacity, influent concentration of chemical oxygen demand (COD), and influent ratio of 5-day biochemical oxygen demand to COD (BOD5/COD) affect the potential significantly. In addition, the energy neutrality potential of samples in the subregions differs distinctly. This study proposes the evaluation on the potential of WWTPs’ energy neutrality with 2 KPIs from both perspective of water-energy efficiency and energy self-sufficiency. The results could provide guidance for other WWTPs under optimization for energy neutrality.
Keywords wastewater treatment plants, energy neutrality, data envelopment analysis, comprehensive water-energy efficiency, energy self-sufficiency rate, Yangtze River Economic Belt