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.