Disclosed is a sedimentation tank system including high-rate filtration part and being capable of primary treatment of sewage and wastewater, flow rate adjustment, and treatment of wetweather flow. According to an aspect of the present disclosure, there is provided a sedimentation tank system for removing solids in an influent sewage and wastewater, the sedimentation tank including a filtration part which includes a filter medium and removes solids in the influent sewage and wastewater, a sedimentation tank with a water gate formed at a predetermined height to store sewage and wastewater flowing over the water gate, and an outflow distribution channel that receives, from the filtration part, sewage and wastewater from which solids have been removed, and discharges the same to the outside of the primary sedimentation tank.