frogchem supply only premium grade Welsh Anthracite. It is designed so that the larger anthracite particles are at the top of the filter and the smaller sand particles are at the bottom of the filter.
This has several advantages over a single media filter. It results in increased filtration rates, longer filter run times and reduced backwash water consumption. It is used in water filtration for the removal of algae, turbidity and bacteria.
A bed of anthracite placed on top of the sand layer provides the filter with larger grain particles to the surface of the filter which delays binding and pressure drop across the filter. It also provides a larger reservoir in which the floc may be held before backwashing.