Double-layer underground water treatment system

The invention relates to a double-layer underground water treatment system, which belongs to the technical field of water treatment, and comprises a pre-sedimentation tank and a coagulation tank arranged above the pre-sedimentation tank, the water inlet end of the coagulation tank is communicated with the water outlet end of the pre-sedimentation tank through a water lifting pipeline with a water lifting pump; a magnetic flocculation basin is also communicated between the coagulating basin and the water pumping pipeline; the coagulating basin is divided into a flocculation zone, a transition zone and an advection zone in sequence from a water inlet end to a water outlet end; and inclined tube packing is arranged in the transition area. Underground water is pre-settled by adopting a lower pre-settling tank, and a settled water source is pumped into an upper coagulation tank through a water pumping pipeline for further flocculation; firstly, a magnetic flocculant is added into a magnetic flocculation basin to a