Pressurized Dissolved Air Flotation (PDAF) is a water treatment process that utilizes a combination of dissolved air flotation (DAF) and pressurization techniques to remove suspended solids, oils, greases, and other contaminants from water. It is commonly used in various industries such as wastewater treatment plants, oil refineries, food processing plants, and pulp and paper mills.

The process starts by saturating the water with air under high pressure. This is achieved by injecting air into a pressure vessel, where the air dissolves into the water. The pressurized water is then released into a flotation tank, which is typically equipped with a system of fine bubbles diffusers or injectors. As the pressure is reduced, the dissolved air comes out of solution in the form of tiny air bubbles.

These air bubbles attach to the suspended solids and contaminants in the water, forming aggregates known as flocs. The flocs rise to the surface of the flotation tank, forming a layer of sludge, which can be skimmed off using mechanical or hydraulic means. The clarified water is then collected from the bottom of the tank.

One of the advantages of PDAF is its ability to handle high concentrations of solids and contaminants. The pressurization process allows for better saturation of air in the water, resulting in a more efficient flotation and separation of solids. Additionally, the use of pressurization can enhance the removal of fine particles that may be difficult to separate using conventional DAF systems.

PDAF is often chosen for its effectiveness in removing various pollutants, including suspended solids, oils, greases, and heavy metals. It can also be used as a pretreatment step before other processes like membrane filtration or disinfection.