Evaluating the environmental benefits and resource loads of municipal wastewater treatment plants in China

Municipal wastewater treatment plants (MWWTPs) provide clean water for urban areas, but due to the significant use of energy and chemicals, the actual environmental implications remain concerning. An evaluation framework for assessing environmental benefits and resource loads is established using monthly operational data from more than 6200 MWWTPs in China from 2007 to 2020 to determine the sustainable potential of this industry and the determinants. A quantile random forest model is used to objectively obtain the plants' sustainability scores without being affected by differences in treatment conditions. The scores are characterized by major pollutant removal performance, representing environmental benefits, and by electricity and chemical consumption performance, representing resource loads. Each plant is provided with an efficient tool that enables it to clarify its actual contribution and to achieve precise improvements. The results show that pollutant removal is improved by large treatment capacities and rational sequence adjustments, whereas resource consumption is reduced through flexible operational responses and favorable ambient temperatures. Socioeconomic drivers play a regulatory role in the context of natural climate conditions. This grid-level evaluation study quantitatively clarified the actual impacts of MWWTPs by considering both the interactions among internal indicators and the effects of external macro-regional factors, thereby providing a data-driven reference for developing targeted improvement measures for individual plants and for policy makers to promote the sustainable development of the industry.