Various Water Filtration Media and Their Benefits
Ensuring a clean and safe water supply is one of modern society’s greatest challenges. Providing potable water to people can be life saving; providing safe water to business and industry can be process critical. FIltration media come in many shapes and sizes, a full spectrum of which are available from African Pegmatite.
In this article, we will go over some of the common water filtration media and find out how they filter water to make it clean and safe for consumption.
Anthracite is mined from coal that has high carbon content. It is black and glittery and is the densest type of carbon. It is an excellent filter for water filtration. Mines are the preferred sources of good quality Anthracite due to the presence of high carbon content in them.
Anthracite can be used either domestically or for an industrial filtering process. Anthracite is one of the most commonly used water filtering media as its unique shape helps it hold particles in the depths of the filtering bed, whilst being widely available and thus inexpensive. One of the interesting features of anthracite is its ability to hold solid particles, making it an excellent media for both single bed filtration and multi layer filtration. Unlike many other filter types, anthracite is easily disposed of (providing the contaminants trapped within it are non-toxic).
Benefits of Anthracite
- Anthracite allows a higher flow of water than sand filters.
- In the use of anthracite, there is less pressure drop when compared to sand filters.
- Anthracite allows for a faster backwash, (i.e. pumping water backwards through the filter media) than most filter media.
One of the major uses of anthracite filtration is in desalination plants, where the porous nature of the material renders it an ideal material to filter debris - which can include anything from small aquatic organisms and plant life through to microplastics and gravel. Anthracite is not responsible for desalination itself but is used as part of a dual media setup alongside other filtration apparatus to protect the semipermeable membrane used for reverse osmosis desalination of seawater. This crucial filtration phase is important as a blocked membrane cannot effect desalination on the water at all - a desalination plant would be useless without effective filtration. Another key application for anthracite is in dual media filters alongside garnet in solvent extraction electrowinning processes.
Another name for activated glass is activated filter media. It was developed to replace classical sand filtration methods. It is made from glass sourced from recycled glass bottles. The glass is granulated into the right sizes for the job with the appropriate manufacturing process. The glass is then activated to increase its surface area significantly. The surface area is then introduced to negative charges, so it attracts organic and smaller particles in the water. Activated glass is often associated with superior filtration of smaller particles when compared with silica sand or plain sand filtration.
Activated glass can be used for both domestic and industrial filtration processes. It is widely used in sewage treatment plants as a substitute for sand. The activated glass has permanent metal oxide catalysts which make the glass self-cleaning.
Benefits of Activated Glass.
- Activated glass is cheaper and lasts longer than sand filters.
- Its unique density allows it to be easily combined with other filtration media.
- It is also self-restoring, which means bacteria will find it difficult to survive on it.
Desolidex and Acti Desolidex
Desolidex and Acti Desolidex are two closely related types of activated glass water filters from African Pegmatite.
Desolidex is a non-crystalline filter medium made from 100% recycled crushed glass. Because of the recycled nature, its manufacturing process is regarded as environmentally sustainable, in addition to reducing landfill requirements. It has a smoother surface than sand and is less dense, so offers superior filtration. The material has a bulk density of 1.14 g cm-3, with an effective size of 0.60 to 0.65 mm; and a uniformity coefficient of 1.40 to 1.65. Such values mean that quality filtration is easily achieved in any deployment.
In terms of operational performance, in-house testing reveals that Desolidex lasts five times longer than sand whilst requiring 16% less material. Filtration occurs from top to bottom, enhancing the overall capacity for filtration and contaminant load, further enhanced by Desolidex’s low packing density compared to sand.
Service flow rate for Desolidex is typically in the range of 10 to 30 m3 m-2 h-1 (cubic metres per square metre per hour) at 100 to 180 kPa, over a bed depth as little as 500 mm.
In comparison, Acti Desolidex is produced to a larger particle size making it better suited to less fine filtration applications and most suited to suspended solids removal in advance of an industrial process or other fine filtration stages. In terms of flow rate, Acti Desolidex operates at similar values as Desolidex, but boasting significantly reduced backwashing and regeneration requirements, whilst operating at a higher backwash rate. Acti Desolidex comfortably operates in the 8 to 12 m3 m-2 h-1 regime.
Silica sand was first used as a water filtering media in 1804, by John Gibb. The use of this media took over two decades to polish to perfection. The United Kingdom currently uses four ranks of silica sand for its water filtration processes.
Silica sands that are appropriate for filtration have a sub-angular or round shape. This shape makes it the perfect water filtration media for drinking water. It works by capturing solids that are left suspended in water. The nature of silica makes it very durable and hard to wear down. This means it can be graded effectively for quality filtering. Silica is however limited in it’s application and being replaced with activated filter media and activated glass filter media due to its longer lifespan and finer micron filtering potential.
Benefits of Silica Sand.
- Its unique nature allows it to be used across various industries such as paper processing, chemical processing, and power generation.
- It can also be used in wastewater treatments.
- Silica is readily available, making it a cheap medium of water filtration.
Silica sand is used in a variety of filtration settings. Oftentimes layered on top of coarse sand or gravel, silica sand provides effective filtration even at high pressures and flow rates. One of the many advantages of silica, aside from its wide availability and broad tolerance to mild chemical attack, is that it has a highly efficient packing efficiency. This means that robust filtration setups can be easily achieved with silica sand.
An activated carbon filter is made from powdered or granular carbon. This carbon is treated to be very porous. It is made to be hollow and has a large surface area. The large surface area allows it to adsorb contaminants better than regular carbon. Adsorption occurs when the organic contaminant chemically bonds with the activated carbon. As a result, the water is made cleaner. The porosity of the activated carbon is directly proportional to the number of contaminants it can remove.
Activated carbon can also be used for air purification. It helps prevents the triggering of allergies and traps allergens and impurities such as hair, lint, and dust.
In regards to water filtration, activated carbon can be used in two ways; Bed Filtration and Secondary filtration. Bed filtration involves outfitting existing filter units with a new bed or replacing the filter medium in a bed with activated carbon. Secondary filtration involves using activated carbon as a second means of filtering water after using the main method of filtration.
Benefits of Activated Carbon
- Activated carbon filters are not only cheap, but they also remove the metallic taste of tap water.
- They are also quite easy to maintain.
- Activated carbon does not filter healthy minerals from the water flowing through it.
Maddox is produced from pure manganese ore that has been heat treated in a proprietary fashion. The result is a heterogeneous catalyst that is able to cause the removal from solution of dissolved iron compounds (such as salts of iron which would be toxic if ingested), as per the ionic equations below.
2Fe2+ + MnO2 + 2H2O ⇌ 2Fe3+ + Mn2+ + 4OH-
Mn2+ + MnO2 + 2H2O ⇌ 2Mn3+ + 4OH-
Maddox provides an immobilised source of high oxidation state manganese which oxidises iron(ii) to iron(iii). Iron(iii) and manganese(iii) are poorly water soluble and thus ‘crash’ out of solution and can be removed using simple size exclusion filtration, such as activated glass or carbon. Maddox can therefore be described as an in-line filter. Maddox is tolerant of high operating volumes and pressures, is easily regenerated and operates over a wide range of pH values, making it ideally suited for upstream pre-treatment ahead of an industrial process.
Maddox is popularly referred to as a type of Green Sand. Maddox has been developed over many years for the original green sand into a ion exchange catalyst which has a lot more applications and more effective. It is called Green Sand because it contains a large percentage of the mineral Glauconite. The chemical is usually greenish-black or bluish-green. The compound was first noticed to have water filtration abilities in the 1900s.
The use of Maddox was encouraged as it was found to be a more efficient filter for dissolved salts. The salts it dissolves include iron, arsenic, manganese, and alumina. South Africa prevalently uses Maddox as its primary water filter media due to large deposits of salts in the country’s water bodies. Most of the country’s water treatment processes use Maddox to help with the filtration.
Benefits of Maddox
- Maddox is a highly effective media for removing certain elements and their salts from water.
- Maddox is very useful for both the filtration and removal of tannins, chlorides and iron.
- Cost effective compared to alternatives in the market while having a long lifespan with regeneration possible for the media.
Magnetite is a naturally occurring ore of iron. It is black and can be found in aggregates in nature. Besides from being used as a water filtration medium, it is also used in coal washing processes. Likewise, it is integral for making compasses and other navigation devices.
Magnetite has a positive surface charge. This positive surface charge attracts the negative charge of the materials present in the water. Thereby eliminating the turbidity of the water and removing the harmful elements in it. Magnetite is often used in conjunction with other filter media, such as quartz sand and anthracite. It is generally used to provide support for the mixed layering.
Benefits of Magnetite
- Magnetite’s sorbent nature makes it great for removing arsenic from water.
- It is also very effective for removing metals and their oxides from water.
- It also allows for the easy backwashing of water.
Depathex is a water filtration application which removes dangerous pathogens from water, making it safe for drinking. Safe drinking water increases human life expectancy and therefore water purification is a high priority. Not only is it used to purify drinking water for humans, it has also been used for agricultural uses, cleaning contaminated water which has had negative effects on the life of animals.
Depathex is an activated zeolite that has been impregnated with granular silver. The porous nature of the zeolite ensures filtration and entrapment of contaminants and pathogens, and the silver is highly effective as an antimicrobial and antibacterial agent. The silver is immobilised within the zeolite, ensuring no leaching of the silver into the water supply, avoiding potential downstream problems.
For over a period of 5 years this product has been researched extensively and tested, which revealed that Depathex completely removes Coliforms and E-Coli.
Benefits of Depathex
- Cleans and purifies hazardous water for human use
- Thoroughly tested and proven to eliminate a broad spectrum of known pathogens
- The provision of clean, safe water is essential for human health and the efficient running of many industrial processes
- Various filtration media are suited to various contamination types, providing anything from simple size exclusion filtration through to heavy metal removal and immobilisation of water borne pathogens
- Filtration media supplied by African Pegmatite come in many shapes and sizes, well suited to long and short term applications that are able to withstand high throughput rates, for repeated uses
African Pegmatite is the go-to industrial partner for the production and supply of market leading water filtration media. Proudly boasting the broadest selection of superior filtration media, processed in-house to exacting specifications, African Pegmatite can assure quality for any project, from day one.