To provide a composite carbide flocculant which forms large floc and has large sedimentation velocity and to provide a waste water treatment system using the composite carbide flocculant.SOLUTION: A composite flocculant comprising carbide flocculant and water-soluble polymer flocculant is added to objective water to perform flocculation, COD inspection of filtration sample prepared by filtering liquid after flocculation with stainless mesh of 600 mesh is performed according to consignment, as the result, the objective water is 74 ppm, and filtrate after performing flocculation with the carbide flocculant and water-soluble polymer flocculant is 22 to 26 ppm. Discharge water (waste water) at first is caused to precipitate solid matter in a sedimentation tank 31, subsequently, is guided to a bubble generation tank 32, before or after the process, the composite flocculant, that is, the carbide flocculant and the water-soluble polymer flocculant are added to discharge water. Subsequently, discharge water is guided to a flocculation tank 33, subsequently, is guided to an aerobic treatment tank 34 and lastly is guided to a final sedimentation tank 35 and supernatant liquid is discharged.SELECTED DRAWING: Figure 1
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