This study focuses on the sewage treatment plant in the central urban area of a specific city. Through the analysis of operational data from the sewage treatment plant and supplementary water quality sampling and testing data, the study systematically investigates the issues within the sewage system serving the plant. The results indicate that the sewage treatment plant faces challenges related to significant fluctuations in influent water flow and instances of extraneous water infiltration. Deficiencies in the construction of the sewage pipeline network within the service area are identified, leading to the entry of river water through discharge outlets, thereby reducing pollutant concentrations in the incoming sewage. The findings of this research hold positive significance for guiding improvements in the quality and efficiency of services within the sewage treatment plant’s service area.