The Filtering Process
Filtering with media filters, also known as depth filtration, is
done by filtering water through a thick layer of graded
particles, called the filter bed. These particles can be sand,
gravel or other granular materials. The filtration degree depends
on the effective size of the bedding and the water velocity through
the filter.
Raw water enters from the filter inlet (1) and percolates through
the filter bed (2). Suspended materials come into contact and
attach to the media particles. Clean water flows through the
filtration nozzles (3) and out of the filter via the outlet valve
(4).
The gradual dirt buildup in the filter bed causes an increase in
the pressure differential across the filter and when it reaches its
maximum design value, a cleaning process should be performed. In
automatic media filter installations a pressure differential switch
senses the pressure differential and when it reaches a preset
value, the self cleaning process begins.