| The novel multiphase pump (NIKNI pump) was applied to produce micro-bubble, of which diameter was about 20-30μm. The pump has advantages of convenience, low energy consumption and little occupied area. In this paper, the pump was assembly to dissolved air floatation apparatus for the study of adding oxygen into water. Micro-bubble and ferrate which is a kind of super oxidants were used to treat with sewage which contains solid particles.In this paper, most of the indissoluble solid particles could be removed by floatation of micro-bubble in the sewage. Then ferrate was added into the sewage to oxidize the organic pollutions, by which the organic pollution could be treated with step by step. So the dosage of oxidants could be decreased. In the process of purify, the interfacial chemistry principles of multiphase among gas, liquid and solid were observed. When numerous bubbles stay in the water , the high dispersed interface between gas and liquid can form, whose effects involve such as floatation, oxidation, enriching the oxygen of water. Ferrate is a kind of novel green reagent for water purify, holding stronger oxidation ability than conventional Cl-oxidant. So it can be used to degrade the substance which is difficult to be degraded by other oxidants.The solution of ferrate was produced by electrolysis method in this paper, and using the agar gel as septum which was not reported. The factors that effect the concentration of ferrate and electric current efficiency were studied, such as anode material, electric current density.The urban sewage was treated by the joint technology. The conditions of floatation and influence of pH and ferrate dosage on oxidation were studied. The results indicate that removal efficiency of SS is 64%-86%, removal efficiency of turbid is 73%-91%, removal efficiency of COD is 60%, and then after ferrate oxidization, removal efficiency of COD changes to 70%, removal efficiency of turbid increases to 95%.
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