SILICA SANDS
Use of silica sand filtration in water treatment and refinement systems dates back late 19th century. These filters are used in majority of refinery systems in Iran, especially the old ones. These filters consist of a silica sand layer which is placed on one or two sand layers. Every square meter of these filters which are also called single-layer filters have the capacity to filter at most 120 to 140 cubic meters per day.