Chemical adding system of high-density sedimentation tank

The utility model belongs to the technical field of municipal water supply and sewage treatment, and discloses a high-density sedimentation tank dosing system which comprises a coagulation zone, a flocculation zone and a sedimentation zone which are communicated in sequence. And a polyaluminum chloride (PAC) dosing system and a ferric trichloride (FeCl3) dosing system are simultaneously mounted in the coagulation region. The coagulation zone is a semi-underground water tank, a ferric trichloride adding stirrer is arranged at the position 2.5 m below the water tank where the coagulation zone is located, and a FeCl3 adding point is arranged at the position 1 m above the position where the FeCl3 adding stirrer is located; a PAC adding stirrer is arranged at a position 2.5 m below the inside of the coagulation area, and a PAC adding point is arranged at a position 1 m above the position of the PAC adding stirrer. When the water inlet chromaticity is relatively good, a medicament adding mode of FeCl3 and polyacryl