A media filter is a type of filter that uses a bed of

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a soil texture, textur ...

peat Peat (), also known as turf (), is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. The peatland ecosystem covers and is the most efficien ...

, shredded tires, foam, crushed glass, geo-textile fabric, anthracite, crushed

granite Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies und ...

or other material to filter water for drinking, swimming pools,

aquaculture Aquaculture (less commonly spelled aquiculture), also known as aquafarming, is the controlled cultivation ("farming") of aquatic organisms such as fish, crustaceans, mollusks, algae and other organisms of value such as aquatic plants (e.g. lotus ...

irrigation Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been dev ...

, stormwater management, oil and gas operations, and other applications.

Design

One design brings the water in the top of a container through a "header" which distributes the water evenly. The filter "media" start with fine sand on the top and then becomes gradually coarser sand in a number of layers followed by gravel on the bottom, in gradually larger sizes. The top sand physically removes particles from the water. The job of the subsequent layers is to support the finer layer above and provide efficient drainage. As particles become trapped in the media, the differential pressure across the bed increases. Periodically, a backwash may be initiated to remove the solids trapped in the bed. During backwash, flow is directed in the opposite direction from normal flow. In multi-media filters, the layers in the media re-stratify due to density differences prior to resuming normal filtration.

Uses

Drinking water

Municipal drinking water systems often use a

rapid sand filter The rapid sand filter or rapid gravity filter is a type of filter used in water purification and is commonly used in municipal drinking water facilities as part of a multiple-stage treatment system. Rapid sand filters were first developed in th ...

and/or a slow sand filter for purification. Silica sand is the most widely used medium in such filters. Anthracite coal, garnet sand, ilmenite, granular activated carbon, manganese green sand and crushed recycled glass are among the alternative filter media used.

Stormwater

Media filters are used to protect

water quality Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through ...

in streams,

river A river is a natural flowing watercourse, usually freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the ...

s, and

lake A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much lar ...

s. They can be effective at removing pollutants in stormwater such as suspended solids and

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ea ...

. Sand is the most common filter material. In other filters, sometimes called "organic filters,"

wood chips Woodchips are small- to medium-sized pieces of wood formed by cutting or chipping larger pieces of wood such as trees, branches, logging residues, stumps, roots, and wood waste. Woodchips may be used as a biomass solid fuel and are raw mater ...

or leaf mold may be used.''ibid.,'
Section 3.3.3: "Organic Filter."

Sewage and wastewater

Media filters are also used for cleaning the effluent from septic tanks and primary settlement tanks. The materials commonly used are sand, peat and natural stone fibre.

Oil and gas industry

The oil and gas industry uses media filters for various purposes in both upstream and downstream operations. Nut shell filters are commonly used as a tertiary oil removal step for treatment of produced water. Sand filters are often used to remove fine solids following biological treatment and clarification of

oil refinery An oil refinery or petroleum refinery is an industrial processes, industrial process Factory, plant where petroleum (crude oil) is transformed and refining, refined into useful products such as gasoline (petrol), diesel fuel, asphalt, asphalt ...

wastewater. Multi-media filters are used for removing suspended solids from both produced water and refinery wastewater. The materials commonly used in multi-media filters are gravel, sand, garnet, and anthracite.

References

__notoc__ {{Stormwater structures Environmental engineering Irrigation Water filters Stormwater management References Nalco Water, an Ecolab Company. Nalco Water Handbook, Fourth Edition (McGraw-Hill Education: New York, Chicago, San Francisco, Athens, London, Madrid, Mexico City, Milan, New Delhi, Singapore, Sydney, Toronto, 2018). https://www.accessengineeringlibrary.com/content/book/9781259860973