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 usually defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural ...

peat Peat is an accumulation of partially Decomposition, decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, Moorland, moors, or muskegs. ''Sphagnum'' moss, also called peat moss, is one of the most ...

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

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, 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 coo ...

or other material to filter water for drinking,

swimming pool A swimming pool, swimming bath, wading pool, paddling pool, or simply pool, is a structure designed to hold water to enable Human swimming, swimming and associated activities. Pools can be built into the ground (in-ground pools) or built abo ...

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. Nelu ...

irrigation Irrigation (also referred to as watering of plants) 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 bee ...

, stormwater management, oil and gas operations, and other applications. Each layer of media is designed to filter out specific types and sizes of particles, allowing for more efficient and effective removal of contaminants.

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. Multimedia filter can remove particles down to 10-25 microns.

Advantages and disadvantages

Advantages of multimedia filters

# Multimedia filters use multiple layers of different filter media to achieve more effective and efficient filtration than single-media filters like sand filters. # They can remove a wider range of particle sizes and types than single-media filters, resulting in more efficient filtration and longer filter life. # They are effective at removing suspended solids, turbidity, and other contaminants from water. # They can be used for a wide range of flow rates and particle sizes. They can be easily backwashed to clean the filter media and restore filtration efficiency. # They require little to no electricity to operate.

Disadvantages of multimedia filters

# Multimedia filters have a higher capital cost compared to single-media filters like sand filters. # They have a larger footprint and require more space than single-media filters. # They may not be effective at removing some types of contaminants, such as dissolved organic compounds and bacteria. # They may require pre-treatment to remove large particles or debris that could clog the filter media. # They can create waste material (backwash water) that needs to be treated or disposed of properly.

Uses

Drinking water

Media filters are used in drinking water treatment, where multimedia filters are used as a primary or secondary filtration step to remove a wider range of particle sizes and types than sand filters, including organic matter and smaller particles. Municipal drinking water systems often use a rapid sand filter 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 tr ...

stream A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a strea ...

river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...

s, and

lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...

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

phosphorus Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...

. Sand is the most common filter material. In other filters, sometimes called "organic filters," wood chips 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 products such as gasoline (petrol), diesel fuel, Bitumen, asphalt base, ...

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