92Dual-media Filter
The most commonly used filter type in the conventional treatment process is a dual-media filter
comprised of anthracite and sand; however, mono-media (sand), multi-media (garnet, anthracite,
and sand), and other media configurations, including the use of granular activated carbon, are also
used in drinking water treatment.
During filtration, the majority of suspended particles are removed in the top portion of the filter
media. Filters are backwashed to dislodge and remove particles trapped within the filter bed, to
reduce head loss (pressure build up), and to keep the filter media clean.