As an efficient and widely-used water treatment solution, dissolved air flotation (DAF) systems are currently employed in water supply, industrial wastewater treatment, and municipal sewage management. Compared to other solid-liquid separation technologies, DAF systems offer distinct advantages including cost-effectiveness, compact design, and high automation levels. Furthermore, their diverse configurations enable users to select and implement the most suitable solutions based on specific wastewater treatment processes, water quality parameters, and flow characteristics.

One of the more common air flotation devices is the electrolytic air flotation device, which mainly uses insoluble anode and cathode to directly electrolyze wastewater, and relies on the tiny bubbles of hydrogen and oxygen produced by electrolysis to carry the flocculated suspended solids to the water surface, achieving the purpose of solid-liquid separation.

Electrolytic flotation equipment removes a wide range of pollutants and exhibits oxidation, decolorization, and sterilization effects. It demonstrates strong adaptability to variations in wastewater load, generates minimal sludge, and produces no noise. However, the equipment also has drawbacks such as high electrolysis energy consumption, significant electrode plate wear, and elevated operating costs, which are the primary limitations restricting its application.

Another type is the air dispersion flotation device, which utilizes the vacuum effect created by the centrifugal force of a high-speed rotating impeller to draw air into the system, forming fine air bubbles that disperse in the water. As these bubbles rise from the pool bottom and carry suspended solids to the surface, solid-liquid separation is achieved. Currently, air dispersion flotation equipment has been widely adopted in various small-scale wastewater treatment projects, including paint production, leather tanning, oil refining, dyeing, chemical processing, dairy processing, fiber manufacturing, paper production, textile industry, mechanical processing, and municipal sewage treatment.

The dissolved air vacuum flotation equipment is a kind of air flotation equipment which is gradually eliminated. Its advantage is that the formation of bubbles, the adhesion of bubbles to particles and the flotation of bubbles and flocculation are all carried out in a stable environment, the possibility of flocculation destruction is small, and the energy consumption of the whole air flotation process is small.

However, the dissolved air vacuum flotation equipment has more obvious disadvantages, namely the limited dissolved air capacity in water, making it unsuitable for wastewater containing suspended solids with concentrations exceeding 250-300 mg/L. Additionally, it requires a sealed container equipped with a sludge scraping mechanism, resulting in a complex structure. Consequently, its practical application in engineering is relatively limited.

However, the most widely used type is the pressurized dissolved air flotation (DAF) system, which is versatile for treating various wastewater streams, particularly oily wastewater, sludge thickening, and water supply treatment. Depending on the types, properties, and treatment efficiency of suspended solids in the raw water, DAF systems are categorized into three types: fully pressurized DAF, partially pressurized DAF, and recirculating pressurized DAF.