Sand filter

Sand filter separation is based on the size of the particles.

In a sand filter, a container or vessel is filled with filter media (sand). The treated liquid flows from top to bottom through the filter media.

The selection of fine grains of sand leaves little clear space between the sand grains and the sludge (suspended solids) contained in the treated fluid will be blocked. The fluid itself will pass through the grains of sand.

Usually, a sand filter is filled with different types of sand (filter media) in order to obtain a good filtration without an excess pressure drop.

It is also recommended to add a layer of anthracite in order to obtain a good distribution of the liquid.

Often sand filters under pressure (where fluid is pumped through) are selected, but sometimes gravity sand filters are also used.

Backwashing is used to remove the pollution (sludge).

In most cases a sand filter is used as a batch system:

• Filtration of the liquid
• Backwashing (to remove the sludge)
• Filtration of the liquid

In addition, there are also continuous sand filters, in which backwashing is not necessary.

A sand filter can be used for polishing after a waste water treatment, as the only filtration step in the purification, as pre-purification for an ultra-filtration, etc.

PCA can help you with this technology, both in design and construction of the installation.