Construction of a Block-Based Water-Level Monitoring System for RDII Management in a Separate Sewer System

In a separate sewer system designed to independently discharge sewage and stormwater, operational issues such as sewage manhole overflow and overloading of the sewage treatment plant capacity can arise during rainfall events owing to Rainfall-Derived Inflow and Infiltration (RDII) into the sewage pipelines. Although various management strategies for RDII have been studied both domestically and internationally, research on monitoring systems that can precisely identify specific locations where RDII occurs remains insufficient. Therefore, this study analyzed the shortcomings of the existing water-level monitoring system using a case study of City A, which was designed as a separate sewer system. To efficiently manage RDII, we propose a methodology for establishing a block-based water-level monitoring system divided into large, middle, and small blocks, inspired by the block system concept used in water supply networks. By conducting water-level observations at the exits of the middle and small blocks, the specific locations of RDII occurrence can be identified. This approach is expected to facilitate effective and prompt countermeasures by accurately identifying the locations where RDII occurs.