A DAF is a gravity separation system that uses air bubbles in a wastewater holding tank to help float insoluble materials to the surface so they can be removed. Some materials that are heavier than water can also be removed if chemical flocculents are used. The flocculents cause these materials to join together in clusters that are lighter than water and therefore float. Pollutants are concentrated in the material that accumulates on the surface, called the float. Other names for the float include DAF float, skimmings, or sludge.
Note that soluble contaminants such as sugar are not usually removed by the system, although they are occasionally trapped in the float along with other particles.