Performance Evaluation of Sewer System Upgrade in an Old Residential Area in Ningbo, China

Abstract

The aging of sewer networks in old residential neighborhoods in China causes frequent problems with their integrity and functionality, such as sanitary sewer overflows and hydraulic overloading of wastewater treatment plants. In order to assess the performance of the sewer system in an old residential area in Ningbo, China, and to evaluate the effectiveness of the sewer system upgrade, the sewer system was continuously monitored for about 8 months. The quantity and quality of wastewater were comprehensively analyzed. The rainfall-derived inflow and infiltration (RDII) characterization was identified in the sewershed by using the R-value method and the triangle method. The R-values before and after the sewer upgrade were about 28% and 7%, respectively. The effects of the sewer upgrade were also quantified through comparing the concentration of pollutants before and after the program. The findings of this study will help to understand the performance of small-scale urban drainage systems, especially in old residential areas and/or in developing countries, and to provide guidance for future system upgrades.