Farmland water returning and draining treatment device

The invention relates to a farmland water returning and discharging treatment device which comprises an equipment body, a water inlet and a water outlet are formed in the equipment body, and a processor is arranged on the equipment body; the grid filter screen is detachably connected to the position, close to the water inlet, of the equipment body and used for removing large-particle impurities such as weeds and gravels; a water retaining assembly; the filter assembly is arranged at the downstream of the filter assembly and is used for prolonging the recession retention time and increasing the recession oxygen content; a nitrogen and phosphorus removal assembly; the nitrogen and phosphorus removal assembly is arranged on the downstream of the water retaining assembly and used for removing nitrogen and phosphorus nutritive salt in the recession; the sedimentation tank is detachably connected to the bottom of the equipment main body and is used for removing fine impurities such as silt; and the purification and