Dissolved air flotation technology has been widely used in water supply and drainage and wastewater treatment in recent years. It can effectively remove the light flocs which are difficult to precipitate in wastewater. It has the advantages of large processing capacity, high efficiency, less land occupation and wide application range. It is widely used in petroleum, chemical, printing and dyeing, papermaking, refining, leather, steel, machining, starch, food and other sewage treatment