AFM® Activated Filter Media Independent performance test results, January 2014* Introduction The following report summarises the performance test results of Dryden Aqua AFM®, quartz sand and other glass filter media commonly on the market. All work was conducted by IFTS (Institut de la Filtration et des Techniques Séparatives www.ifts-sls.com) in France, recognised as one of the leading independent accredited laboratories on water filtration media worldwide.
Filter media tested
AFM is a highly engineered filtration media manufactured from green container glass as a raw material.
• EGFM by DMS crushed glass media manufactured by implosion, England
Review of data
• Vitrosphere spherical glass balls, Germany
®
Three factors are important in media bed filtration:
Products tested were as follows: • AFM® Dryden Aqua, Scotland • Quartz Sand from the Leighton Buzzard deposit, England • Garofiltre crushed glass media, France
• Bioma crushed glass media, Spain • Astral crushed glass media, Spain
1. Mechanical filtration 2. Adsorption reactions 3. Performance with coagulation and flocculation The following report relates only to the mechanical filtration performance. The tests were conducted on clean media. It is known that sand and non-activated crushed glass media will become a biofilter over a period of a few months. The bacteria adversely affect mechanical filtration performance and promote wormhole channelling. Bio fouling and there for channelling does not happen with AFM®.
*Tests conducted by IFTS: www.ifts-sls.com
Test 1: Particle size removal efficiency
AFM® will remove 80 % of all particles in the water down to 4.5 microns. The best a very high quality sand can achieve is 8 microns. The results were collected from filters operated at 20 m/hr filtration velocity with no flocculation. Therefore the results are a direct comparison between the different filtration media. The chemistry of the glass, the particle shape and especially the activation process give AFM® the important properties to clearly outperform sand and glass sand filter media .The large surface has a strong negative charge to adsorb organics and small particles. The surface also has metal oxide catalysts which produce free radicals and thus a high redox potential. Therefore AFM® is self-disinfecting. AFM® prevents bacteria from settling to make it a unique, bio-resistant filter material.
Graph 1: Smallest particles removed at 80 % performance at 20 m/hr velocity and no flocculation AFM®
Sand 16/30
Garo
EGFM
Astral
Bioma
Vitro Sphere
Smallest particle removed microns
0 5 AFM®
10
Sand 16/30
15
Garo
20
EGFM
25
Astral
30
Bioma
35
Vitro Sphere
40 45 50 Source: IFTS test data, France, 2014
Summary of filter media performance at 5 microns, water flow 20 m/hr
Efficiency at 5 microns Removals %
Differential pressure Injected mass
AFM®
Sand 16/30
Garo
Astral
Bioma
EGFM
Vitrosphere
Initial %
76.78
55.30
77.51
79.91
39.02
76.65
49.00
Final %
82.40
74.85
63.97
39.04
3.70
53.70
0.00
Average %
81.30
72.97
65.61
49.35
7.45
58.03
0.05
Initial mbar
155.00
149.00
88.00
124.00
111.00
222.00
121.00
Final mbar
934.00
891.00
808.00
550.00
511.00
934.00
123.00
Grams
109.00
133.00
266.00
209.00
400.00
109.00
201.00
Source: IFTS test data, France, 2014
Comments AFM® and sand proved to be the most efficient as none of the other media could achieve a high end of test pressure due to retained solids break-through. AFM® was also the best with respect to average and final filtration performance at 5 microns, at a filtration velocity of 20 m/hr. The tests were conducted in un-clarified water.
Test 2: Differential pressure vs Injected mass
ISO CTD particles were injected into the process water to test the capacity of the media to remove particles from the water. As the particles are removed from suspension, pressure should gradually build up in the filter bed until it eventually blocks. Only the AFM® and sand filter beds blocked, all other media allowed particles to break through the filter bed and return to the process water. Ability to retain particles is very important in any filtration system. In drinking water and swimming pool systems, where crypto-sporidiosis presents a significant disease risk, filters must be stable and able to retain parasite’s. Sand and AFM® were the only two products to offer a stable filtration barrier. Graph pressurevsvsinjected injected mass Graph2:3:Differential differential pressure mass 1400
Differential Pressure mbar
1200
1000 AFM® Sand 16/30
800
Astral Garo
600
Bioma EGFM Vitrosphere
400
200
0 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87
Injected mass grams (g)
Source: IFTS test data, France, 2014
The quantity of material released over time was measured for each of the various media. The graphical data for backwash efficiency confirms that both sand and AFM® achieved 97 % backwash efficiency. The closest glass media was Garofiltre at 93 % followed by Astral at 92 % and EGFM at 88 %. What goes into a filter must come back out, if this does not happen the retained organic matter will be subjected to bacterial metabolism and eventually the filter media will bio-coagulate due to an accumulation of alginates secreted by bacteria and mineralised biofilm layer.
Graph 3: Back-wash efficiency Graph 4: back-wash efficiency Percentage or partilces eluted during backwash %
Test 3: Backwash efficiency
100.00
90.00
80.00 AFM®
70.00
Sand 16/30 Astral Garo
60.00
Bioma EGFM 50.00
Vitrosphere
40.00
30.00 0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
Time in minutes for back-wash
Source: IFTS test data, France, 2014
The backwash profile for AFM® follows a reproducible and predictable sine curve. The sand presents an erratic and non-predictable backwash profile. Also when the area below the curve is measured it confirms that 30 % more solids have been eluted from the AFM® filter in comparison to the sand filter operating under identical conditions. Experience demonstrates that AFM® backwash efficiency is sustainable whereas bioaccumulation leads to a deterioration of performance in other media. This affects both performance and running cost, as progressively more water is required even for an incomplete backwash of other media.
Graph 4: Back-wash profile for sand and AFM® 70 Turbidity (NTU) of the backwash water
The backwash profiles shown in graph 5 show the quantity of solids discharged from a filter bed during a backwash.
60 50 40
Week 1 Week 2
Sand AFM® Sand AFM®
30 20 10
30 60 90 120 150 180 210 240 270 300 360 420 Backwash time [s] Source: Lyonnais des Eaux
Result discussion Key points • AFM® performed the best in tests, twice as well as the closest crushed glass product and 40 % better than the highest quality sand (see graph 1 & table page 2) • Sand performed better than all other glass media (see graph 1 & table page 2) • All crushed glass products failed the injected mass test leading to discharge of unfiltered material back to the process water with no effective barrier against e.g. cryptosporidium parasites, bacteria or organic matter (see graph 2) • None of the glass products tested backwashed within 6 minutes, the best still retained 8 % of solids, and the worst retained 20 %. This translates to a significantly higher water requirement for backwashing and a higher chlorine demand resulting from retained organic matter (see graph 3)
Conclusion
The test results demonstrate the advantages of AFM® over all other filter media tested. AFM® clearly outperformed high quality quartz sand and any other glass filter media. Chlorine oxidation demand in chlorinated systems and the formation of disinfection by-products relates directly to filtration and backwash efficiency. The data presented confirms a considerable performance advantage of using AFM® over sand and any other glass filter media.
Additional information: What is AFM® activation? AFM® activation is a patent protected 3-stage process during which the surface structure of the glass is changed at a molecular level. Glass is an aluminosilicate, the activation process uses the existing properties of the glass which is why Dryden Aqua only use green container glass. In addition the production process enhances the glass’ properties by: 1. Increasing its catalytic properties 2. Controlling its surface charge density 3. Increasing its surface area 4. Controlling the selective molecular sieve structure of the surface
Picture 1: AFM® surface (500 nm)
www.drydenaqua.com
Picture 2: AFM® surface (2.0 µm)
© Dryden Aqua, 03-2014
Electrochemical adsorption, moleculare sieve adsorption and performance with coagulation and flocculation chemicals will be covered in additional reports in the near future.