Efficiency assessment of pollutants discharged in urban wastewater treatment: Evidence from 68 key cities in China

Abstract

Pollutant removal is a critical procedure for wastewater treatment because it directly determines the effectiveness of wastewater treatment and water conservation. Therefore, assessing pollutant discharge efficiency in wastewater treatment is imperative. In this study, an environmental production technology with a non-radial data envelopment analysis model is developed to examine the discharge efficiency and reduction potential of pollutants in wastewater treatment in 68 key cities by considering the disparity of city scales. By comparing discharge efficiency and reduction targets released in the 12th Five-Year Plan, this study identified the key areas that need to be addressed for wastewater treatment with regard to different city types. Results showed that chemical oxygen demand (COD) and ammonia nitrogen (AN) have similar discharge efficiency values, mainly ranging from 0.5 to 0.7. More specifically, the discharge efficiency of COD is comparatively lower than that of AN. City size generated a positive impact on efficiency improvement. Centralized treatment system is beneficial for achieving the scale effect in wastewater treatment. An examination of the progress of reduction target systems indicated that AN is comparatively inferior in reduction completion. Apart from the technical barriers, this fact is highly related to the willingness and power of the local government. Cities should identify the key areas that need to be addressed and adopt the corresponding reduction strategies by referring to their scales. The findings of this study can facilitate the inclusion of pollution mitigation in the urban agenda, thereby fostering an effective wastewater treatment process and creating a benchmarking framework for governing wastewater pollution.