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　　A decanter is a water collection device that is a floating drainage device that can rise and fall with the water level during drainage.A decanter generally consists of a water collection device,a connecting device,and a transmission device.The drainage characteristic of a decanter is to rise and fall with the change of water level to timely discharge the supernatant without disturbing other water layers in the pool.In order to prevent the floating debris from being discharged with the water,the collection port of the decanter is usually submerged at a certain depth below the water surface,rather than overflowing from the top of the weir like a movable weir.