Analysis of energy consumption for China's urban wastewater treatment plants under stricter effluent quality standards

This study collected operational data from 2021 to 2023 to analyze the specific energy consumption (SEC) distribution and evaluate the impacts of influencing factors on SEC, including geographical region, plant scale, loading rate, treatment technology, and effluent quality. Through Spearman's rank correlation analysis, it is determined that in China, characterizing the SEC by the energy consumption per unit treated wastewater volume is more reliable. The results of statistical analysis indicated that the overall median SEC is 0.38 kWh/m3, representing a remarkable upward trend compared with the level prior to the nationwide effluent quality standard upgrades. Box-plot analysis was employed to investigate the effects of single factors and their two-factor interactions on SEC, and the random forest regression (RFR) algorithm was used to quantify the feature importance of each factor. The results showed that the loading rate emerged as the most robust key determinant of SEC, maintaining a consistent impact power across different groups of factors. The findings illustrate the current energy consumption levels in China's wastewater treatment and may provide insights for optimizing process selection based on expected loading conditions in wastewater treatment plants.