PROBLEM TO BE SOLVED: To provide an aeration technology related to water quality purification by aeration in a sewage treatment plant, an improvement in a water tank inner flow of the whole seafood, plant cultivation and hull friction resistance reduction.SOLUTION: In a through-flow pump of a multiblade in an impeller shape, a clearance is opened on the inner diameter side of an impeller hollow rotary shaft 16 installed on an impeller side plate on the anti-driving side, and a small diameter pipe-shaped nozzle 45 is inserted, and is thrust out to the outside from a sealed bracket 19 connected to the rear end of a bearing 25 for holding a rear end part of a nozzle pipe, and is connected to a pipe 13, and an ultrafine bubble including pressurizing liquid discharged from a booster pump 46 is supplied in the nozzle pipe, and is decompressed-diffused by jetting in an impeller 7 for rotating a jet-like jet flow from the nozzle tip thrust out in the impeller, and is also mixed with a flow in the impeller, so that a discharge flow of a large quantity of ultra-finned bubbles is provided.
