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Amedia filter is a type offilter that uses a bed ofsand,peat, shredded tires, foam, crushed glass, geo-textile fabric,anthracite, crushedgranite or other material to filter water for drinking,swimming pools,aquaculture,irrigation, 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.

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.

1. Multimedia filters use multiple layers of different filter media to achieve more effective and efficient filtration than single-media filters like sand filters.    
2. They can remove a wider range of particle sizes and types than single-media filters, resulting in more efficient filtration and longer filter life.  
3. They are effective at removing suspended solids, turbidity, and other contaminants from water.    
4. 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.    
5. They require little to no electricity to operate.  

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

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 arapid sand filter and/or aslow sand filter forpurification. Silica sand is the most widely used medium in such filters.^[1] Anthracite coal, garnet sand, ilmenite, granular activated carbon, manganese green sand and crushed recycled glass are among the alternative filter media used.^[2]

Media filters are used to protectwater quality instreams,rivers, andlakes. They can be effective at removingpollutants in stormwater such assuspended solids andphosphorus. Sand is the most common filter material.^[3][4] In other filters, sometimes called "organic filters,"wood chips orleaf mold may be used.^[5]

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

Theoil 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 ofproduced water. Sand filters are often used to remove fine solids followingbiological treatment and clarification ofoil refinery 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.^{[citation needed]}

• Biofilter
• Bioretention

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

• Environmental engineering
• Irrigation
• Water filters
• Stormwater management

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