Hydrodynamic characterization and interception-entrainment rates of the DSM-flux – a new technology to monitor CSOs

Combined sewer overflow structures (CSOs) represent an important source of pollution for the receiving water bodies. A significant amount of pollutants is attached to the suspended solid matter. The DSM-flux is an innovative technology conceived to improve CSO (combined sewer overflow) quantity and quality monitoring and, due to its original geometry, to intercept pollutants bounded to suspended matter. This study aims to evaluate the hydrodynamic behavior and particle interception-entrainment performance of the DSM-flux at small scale in controlled laboratory conditions. Flow patterns and turbulence quantities are measured with precision over the whole device and particles interception and entrainment of solid matter are investigated by means of experimental particle transport tests. The results reveal a clear dependence between the interception efficiency and the inflow rate, this efficiency reaching up to 53.6% under low flow conditions. Moreover, a correlation was observed between the deposition areas in the DSM-flux and the regions with low near-base turbulent kinetic energy values, thereby contributing to the hypothesis of an existing relationship between turbulent kinetic energy and entrainment/deposition phenomena. In-situ observations of a full-scale DSM-flux device during a storm event corroborate the laboratory observations, and confirm the capacity of particles interception by the facility.