Sewage treatment system

The utility model relates to a sewage treatment system. The sewage treatment system comprises a biological reaction zone and a sedimentation separation zone, wherein a hydraulic drop-driven biofilm treatment device is arranged above the biological reaction zone, in the hydraulic drop-driven biofilm treatment device, a plurality of paddle plates are arranged on a rotation shaft, the paddle plates are arranged below a sewage feed pipe, a plurality of biofilm bearing discs are also arranged on the rotation shaft and a part of the biofilm bearing discs are immersed below the liquid level. According to the sewage treatment system provided by the utility model, by the energy of sewage entering the tank, the waterwheel-type paddle plates are driven in a hydraulic drop manner to drive the rotation shaft to rotate and thus the biofilm bearing discs operate and the sewage is aerated once. When the water overflows from the paddle plates, the contact surface with the air is also further increased, thereby further aeratin