Portrait of municipal wastewater of China: Inspirations for wastewater collection, treatment and management.

Over the past decades, significant importance has been attached to municipal wastewater treatment in China. But wastewater treatment plants (WWTPs) still grapple with operation inefficiencies due to low influent concentrations. This study comprehensively provides a portrait of Chinese municipal wastewater from the national and province levels, drawing on official data available. The historical trends of main pollutant indexes in WWTPs influent and the corresponding geographical distribution variations during 2007-2020 have been analyzed. Pollutant concentration and wastewater collection rate in northern and western regions were generally higher than southern and eastern regions of China. A wastewater collection rate of approximately 65 % by introducing actual pollutant collection amount has been proposed, demonstrating the practical conditions and problems of Chinese wastewater collection system nowadays. Correlation and redundancy analysis further pinpointed collection rate and rainfall as the paramount factors affecting influent concentrations and pollutant losses, contributing 66.9 % and 29.5 %, respectively. These results indicated that the deteriorated or damaged sewer pipelines, along with mixed or wrong connection of rainwater and wastewater, led to a large amount of extraneous clean water transported into and then treated unnecessarily by WWTPs. A significantly negative correlation between influent chemical oxygen demand (COD) concentration and electricity consumption in WWTPs was disclosed, further emphasizing the importance of increasing influent loading and rehabilitating sewer pipelines to enhance the overall efficiency of wastewater systems. This study helped glean valuable insight into a more efficient and sustainable solution for wastewater treatment and management.