The Principle and Application of Dissolved Air Flotation (DAF)
Dissolved Air Flotation (DAF) is a common water treatment technology used for the removal of suspended solids, fats, and other suspended particles from water. It operates by utilizing the adhesion and buoyancy principles of tiny bubbles, causing the aggregation of suspended particles during the ascent of the bubbles, resulting in their rise to the water's surface. This process facilitates solid-liquid separation and water purification.
The fundamental principles of DAF are as follows:
Within the DAF equipment, tiny bubbles, typically with diameters ranging from 20 to 100 micrometers, are generated by introducing air or other gases into the water. These bubbles are uniformly dispersed throughout the water. As the bubbles ascend in the water, they come into contact with suspended solids and attach to the surfaces of the suspended particles. The attachment of suspended solids increases the density of the bubbles, making the bubble-particle complexes collectively heavier than water, causing them to rise upwards. When the bubble-particle complexes reach the liquid surface, their lower density causes them to float and form a layer of floating sludge. The suspended solids in the floating sludge undergo condensation and aggregation, forming larger clusters that are subsequently removed from the water surface by scrapers or other devices.
The advantages of DAF include efficient removal of suspended solids, fats, and other solid particles, leading to reduced suspended matter content and improved water quality. The process is easy to operate and requires relatively small space. DAF is applicable for treating various types of water, including wastewater, industrial effluents, and drinking water, among others.
