Sewage impurity and oil stain separation device and method for irrigation

The invention relates to a sewage impurity and oil stain separation device for irrigation. The device comprises a water flow collecting box, wherein a metal net conveying belt is arranged in the water flow collecting box, and comprises a first conveying belt and two second conveying belts, the first conveying belt is composed of a first metal slender rod and chain transmission structures at the two ends of the first metal slender rod, the second conveying belt is composed of second metal rods and transmission devices at the two ends of the second metal rods, the second metal rods cover the first metal rod and are perpendicular to the first metal rod, the two ends of the second metal rods are connected with sliding blocks, the sliding blocks are separated from the transmission devices at the positions close to an impurity outlet, and the distance between the adjacent second metal rods is increased. According to the invention, water is treated for multiple purposes such as irrigation and the like so as to be pr