Why AFM Instead of SAND?
We have moved away from the traditional system of offering a river sand as a filtration media to the most advanced filtration media called AFM. Active filter media called as AFM is made up from crushed green glass and it has several unique properties, which are not possessed by sand.
Material of construction
A sand is made up of silica depending on the type & origin of the sand.AFM is produced from waste glass which silica in its purest form. The average silica content in the glass is above 70%. Making it the toughest material and resulting into a nil abrasion loss.
Impact – Nil Abrasion loss & reduction in size of media. Reduced top up & consistent filtration performance.
Size – The size of the grade one media is 0.45 to 1 mm as compared to 0.5 to 1.2 mm of sand. And the uniformity coefficient > 1.3. Which makes this media as the most uniform filtration media available & the uniform particle size distribution of average 0.7 mm gives much finer filtration performance.
Impact – sand grading not required.
Surface areas – Sand has a surface area of 3000 m2/ton where as a AFM has a surface area of 1000000m2/ton. Which makes it a 300 times higher surface area as to that of sand. The higher surface area provides a much finer filtration performance. And better run time.
Impact – Better filtration performance.
Charge on surface – AFM has a negative charge of -70 mV on the surface of it which make it the only media performing by mechanical sieve and also by mechanical adsorption as compared to only mechanical adsorption in sand. Sand has no charge on the surface.
Impact – Consistent performance of the media without drop in performance.
Electron Micro Graphs Of Sand And AFM
Sand has 100% bacteria coverage after 3 days in a drinking water filter.
AFM stays free of biofilm, even after 5 years in sewage effluent Alginates excreted by bacteria coagulate the sand and cause wormhole channeling.
Sphericity & average particle size distribution
AFM has a average Sphericity of greater than 0.8 which no other filter media has. The average particle size distribution is also at 0.6 mm. which provides the most uniform size and structure for the filtration.Impact – AFM can remove upto 86% of 5 micron size particle & upto 91 % of 10 micron particles in filtration. Which gives a filtration performance equivalent to a disc, cartridge or a bag filter. AFM can give the same filtration consistently without any drop in filteration performance.
Dual functioning – AFM is the only media which has a dual performance. AFM in addition to working as a mechanical sieve it also works by mechanical adsorption.
Impact – In normal course of operations activated carbon is always used in addition to a sand filter.
ACF ( activated carbon filter) is installed to remove color, odor and organics from the water by way of passing the water from the media.By using AFM there is no requirement of separate carbon filter. By using AFM as a media in the filtration stage itself we can take care of the color & odor removal.
AFM Application Areas
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