Optimization strategies for urban sewage pipe networks in a representative city in China based on multi-dimensional precision assessment

Abstract

In China, the sewage pipe networks in older central urban areas have been in operation for many years. Although local governments have attached great importance to urban sewage pipe network management, there is still the lack of a precision assessment method to effectively guide the construction, repair or reconstruction of sewage pipe networks for local governments. In this study, Zunyi was selected as a representative example. A multi-dimensional precision assessment system was proposed to explore the challenges in the urban sewage pipe network and guide targeted infrastructure improvements. Breaking through the limitations of traditional assessments, this system delineated 10 drainage zones based on wastewater treatment plant service areas, pipeline distribution, and urban planning. Key metrics—sewage collection rates, pipe network damage rates, and CSO risks—were evaluated under current (2022) and projected (2025) scenarios. The results revealed that the sewage pipe network densities in all zones were lower than those in developed countries, leading to the sewage collection rates being lower than 70% in most zones until 2025. This indicated that many zones in Zunyi required network construction to mitigate direct discharge of sewage. Based on the volume of untreated sewage on sunny days and the risk of CSOs during rainy days, two zones in Huichuan District should be prioritized for construction, repair, or reconstruction. Subsequently, zone III should be constructed or reconstructed due to significant CSOs during heavy rainfall. If local government economic conditions permit, additional sewage pipe networks should be constructed in all zones, except for zones III, IV, and V in Honghuagang District, to enhance sewage collection capacity. This study provides an innovative paradigm for the scientific assessment and efficient governance of urban sewage pipe networks in China and is of great significance for promoting the sustainable development of the urban water environment.