Oxidation ditch is one kind of activated sludge treatment system. Its aeration tank is in a closed ditch type, so it is different from the traditional activated processes in terms of hydraulic flow. It is a circulating flow aeration ditch, also known as circulating aeration tank. The strength of the development of oxidation ditch technology lies in the circulation of the oxidation ditch. Due to this circulation, the oxidation ditch lasts for a long time. In order to form cyclic push flow, the traditional oxidation ditch process generally uses directional rotary brushes or disks. Disadvantages of rotary brushes or disks: The flow velocity at the upper part of the oxidation ditch is relatively high, while the flow velocity at the bottom is very small (especially below 2/3 or 3/4 of the water depth, the mixed liquor has almost no flow velocity), resulting in a large amount of mud accumulation at the bottom of the ditch (sometimes the thickness of the mud accumulation reaches 1.0m ), which greatly reduces the effective volume of the oxidation ditch, reduces the treatment effect, and affects the effluent discharge quality. The Biojet® oxidation ditch process developed by Yangzhou Biojet Environmental Technology Development Co., Ltd. based on the Laval Jet utilizes the technical characteristics of the jet aerator that integrates aeration and push flow functions, and on the one hand the designed effective water depth of the oxidation ditch can be increased and the oxygen transfer rate can be improved; There is no more regular underwater maintenance needed, due to the replacement of the rotary brush or disk with jet aerator.