Wastewater treatment anaerobic reactor

The invention discloses a wastewater treatment anaerobic reactor, which structurally comprises a biogas collecting pipe, a gas-liquid separator, a water outlet pipe, two three-phase separators, a reactor body, a downcomer, a water inlet pipe, a pollution discharge seat, a water distributor and an ascending pipe, the pollution discharge seat is mounted at the bottom of the reactor body, the three-phase separators are arranged at the upper end in the reactor body, and the number of the three-phase separators is two. The the pollution discharge seat is arranged, the gravity of sludge is utilized to apply pressure to the pressure bearing plate to apply force to an air bag, the return device pushes the sludge towards the blow-off pipe through pressure exhaust of the air bag, the return device automatically retracts when reaching a designated position through cooperation of a first spring and a sliding groove, deformation of the return device is prevented, the return device is tightly attached to the mud blocking b