Anthracite
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.
Silica Sand
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.
Activated Carbon
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.
Magnetite
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.
You must be logged in to post a comment.