Filtration System

Filtration methods are used for the physical, mechanical and biological separation of solids from treated water. Filtration takes place after the clarification stage as an additional treatment step to remove any remaining suspended particles and unsettled floc to ensure safe water.

Sand Filtration

Filter sand is naturally occurring sand that is high in silica and low in calcium. It is graded and washed. It can be used independently or as part of a multimedia filter. Sand filters are believed to be the oldest man-made filters and they imitate a common natural filtration technique.

Multimedia Filtration

Multimedia filters consist of several layers usually two to three of different media. The media are loaded by density the densest in the bottom of the tank, the least dense on top. This produces a filter with an excellent flow rate and relatively easy backwash properties that will filter down to ten microns.

The most common media mix is (top to bottom): anthracite, filter sand, garnet and gravel. This is a typical mix, although many others are common.

Anthracite Filtration

Crushed anthracite coal has long been a favourite medium-weight filter for sediment reduction. It is often used with sand and other media in multi-media filters.

Birm Filtration

Birm is a manufactured medium consisting of plastic coated with magnesium oxide. Designed for iron and manganese reduction. It causes iron and manganese to change from a dissolved state to a particulate, as a result, it then it filters out the particulate. Birm can be used with or without an oxidizer. Its success without an oxidizer depends a great deal on the amount of dissolved oxygen in the water.

Garnet Filtration

Garnet is a natural medium used most often in multi-media filters. It is very fine and filters down to the 10-20micron range.

Granular Activated Carbon Filtration

Granular carbon is the standard media filtration for most chemical reduction situations, including chlorine and organic removal. Its high surface area gives it massive adsorptive capacity. It can be manufactured from animal bones, wood, and but most carbon is produced from anthracite coal or coconut shells.

Manganese Greensand Filtration

Manganese greensand is a purple black filtration medium, made from naturally occurring greensand coated with manganese. It serves as a catalyst to precipitate hydrogen sulphide, iron and manganese. It can be continuously regenerated with chlorine and/or a purple liquid called potassium permanganate, or it can be intermittently regenerated with potassium permanganate alone.