AFM WITH RAPID GRAVITY AND PRESSURE SAND FILTER
FILTERATION & POLISHING
The water from the pond is lifted by a pump and passed through a ZPM unit from which it is passed through a PSF which has AFM as a filtration against conventional sand. AFM is specifically selected for the wastewater treatment application of several special features & properties possessed by the product.
AFM (ACTIVATED FILTER MEDIA)
Active filter media (AFM) is a product of Dryden Aqua Research & Development over the last 20 years to replace filter-grade sand. AFM is manufactured from a specific type of glass and processed to provide a hydraulically optimized media in terms of particle shape and particle size distribution. The glass then proceeds through an activation process to increase the surface area by 300 times over crushed glass or sand. The high surface area is negatively charged (zeta potential) to adsorb organics and small particles, the surface also has permanent metal oxide catalysts that give a high redox potential to make AFM self-sterilizing and the only activated glass filter media.
FEATURES OF AFM & OTHER PROPERTIES ARE ENCLOSED HERE WITH
AFM PROPERTIES & BENEFITS
- AFM is an activated amorphous alumino-silicate with a positive charge organic adsorption (OAD) number greater than 10, the activated hydrophilic surface has cation bridging, hydrogen bonding, and entropic interactions with organic molecules.
- High surface electrical charge density Zeta potential > -70mv as measured by kelvin probe analysis.
- Uniformity coefficient better than 1.5
- Sphericity factor better than 0.8
- AFM mechanically removes most particles down to 5 microns.
- Sand surface area, approx 3000m2/ton, AFM surface area >1,000,000 m2/ton
- The high surface negative charge potential helps to adsorb micron and sub-micron particles as well as some dissolved organics.
- AFM rejects bacteria growth and worm-hole channeling
- AFM is capable of very high turbidity loads up to 150 NTU.
- Back wash water requirement reduced by 50%.
- No requirement to replace AFM for the life of the filter.
- AFM removes heavy metals, Iron, Manganese & Arsenic from the water.
- AFM substantially reduces BOD,COD from water.
- AFM removes organic impurities/Natural organics matters from water.
- AFM removes color & odor.
- AFM removes Pseudomonas & Cyclops from water.
WHY AFM FOR FILTERATION SYSTEM?
We have moved away from the traditional system of offering river sand as a filtration media to the most advanced filtration media called AFM.
Active filter media called AFM is made up of crusaded glass and it has several unique properties, which are not possessed by sand.
MATERIAL OF CONSTRUCTION
A sand is made up of silica content ranging from 50 to 60 % depending on the type & origin of the sand. AFM is produced from waste glass which is silica in its purest form. The average silica content in the glass is above 70%. Making it the toughest material and resulting in a nil abrasion loss. The only material It can cut this is diamond.
Impact – Nil Abrasion loss and reduction in size of media. Reduced top-up and consistent filtration performance. Life of the media for more than 15 years.
Size
The size of the grade one media is 0.4 to 1 mm as compared to 0.35 to 1.2 mm of sand. And the uniformity coefficient of < 1.3. This makes this media the most uniform filtration media available & the uniform particle size distribution of an average 0.7 mm gives a 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 a drop in performance.
Biofouling – AFM due to negative charge on its surface liberates free oxygen radical in presence of dissolved oxygen in water. This free oxygen keeps the tasc of keeping the media free from any biofouling and it also kills the bacteria attached to its surface. On a longer run the sand looses it abrasion & due to the polysaccharide glue secretion by the bacteria’s on the surface of the sand there is a consistent drop in the performance of the sand.
Impact – drop in filtration efficiency of the sand. Within 6 – 9 months the filtration efficiency drop of 50% resulting in increased discharged turbidity. In case of AFM the performance is consistent for the entire life of the media.
O2 + H20 ———-> 3O– + OH–
ELECTRON MICROGRAPHS OF SAND AND AFM
NEW SAND
USED SAND AFTER 3 DAYS
Sand has 100% bacteria coverage after 3 days in a drinking water filter
NEW AFM
USED AFM AFTER 5-YEAR
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 an 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 up to 86% of 5-micron size particles & up to 91 % of 10-micron particles in filtration. Which gives a filtration performance equivalent to a disc, cartridge, or bag filter. AFM can give the same filtration consistently without any drop in filtration performance.
DUAL FUNCTIONING
AFM is the only media that has a dual performance. AFM in addition to working as a mechanical sieve also works by mechanical adsorption.
Impact – In the 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 passing the water from the media.
By using AFM with CSF there is no requirement for a separate carbon filter. By using AFM as a media in the filtration stage itself we can take care of the color & odor removal.