What makes AFM ® as effective?
1. Clean Green glass: For AFM ® , we only use green
glass bottle banks and surplus glass from glass
kilns as our raw material in order to insure purity
and traceability. AFM ® is manufactured from pure
green glass because only green glass has the
chemical and physical properties required
by AFM ® .
2. Ideal hydraulic properties: The raw material is
cleaned, washed, sterilised and then reduced in
size to a precise particle size, shape and particle
size distribution. The correct shape is crucial for
the outstanding hydraulic characteristics of AFM ® .
Glass beads or pearls, as well as plates are not
suitable for clean water applications. Glass beads
are not suitable because solids can push their
way through beads. Filter media needs to lock
to provide a barrier. Flat glass or clear glass form
plates which is not suitable because the plates
over-lap to cause a lensing effect in the filter
which promotes channelling down to the out-
side edges of the filter bed. For safety reasons
no dangerous glass splinters are allowed to be
present in the filter material. Our ISO2001-2008
certified manufacturing process together with
quality control of each produced batch in our
laboratory ensures that this is not the case.
3. Activation: AFM ® activation process creates a
meso-porous structure with a huge catalytic
surface area. Typically crushed glass or sand
has a surface area of 3‘000 m 2 per m 3 of media
but activated AFM ® has a surface area of over
1‘000‘000 m 2 per m 3 which is over 300 times
greater surface area for adsorption and catalytic
reactions. Hydroxyl groups on the surface give
AFM ® a strong negative charge known as the
zeta potential that attracts heavy metals and
organic molecules. In the presence of oxygen or
oxidising agents the catalytic surface generates
free radicals that oxidise pollutants and disinfects
the surface of AFM ® .
Comparison quartz, glass sand and AFM ®
1‘000‘000
200‘000
100‘000
0 m 2
400‘000
600‘000
800‘000
AFM ® has an approxi-
mately 300 times
greater surface than
quartz and glass sand.
Comparison m 2 per tonnes
Bottom line:
The chemistry of the glass, the particle shape
and especially the activation process give AFM ®
these important properties to clearly outperform
and outlast sand and glass sand filters.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.
A word about glass sand…
AFM ® has matured over a period of 30 years of
research and developed into a highly engineered
and safe product, certified under European Drin-
king Water regulations and tested under Environ-
mental Technology Verification and validated to
out-perform sand or crushed glass by up to 30 %.
AFM ® is also manufactured in one of the most
sophisticated, computer controlled glass proces-
sing factories in the world.
Like all great ideas and products others try to
follow. Unfortunately, in this case there are some
serious human health and safety issues at risk.
AFM ® is a highly engineered product that is safe
to use but most crushed glass products on the
market are just waste mixed glass from refuse.
Often the glass smells of decaying organic matter,
and may contain contaminants as well as a higher
percentage of fine shards of glass that will get
through the laterals or nozzle of any filter used in
swimming pools.
…and Glass beads
Glass beads are promoted as a good filtration
media for swimming pools. Glass beads are cer-
tainly very clean and safe to use, however a sphere
has the lowest possible surface area and largest
space between the particles than any other shape.
Also as solids build up on the bed the pressure
differential can push them through the bed. For
example it is very easy to push your hand through
a glass bead bed but you can only penetrate a few
millimetres of an AFM ® or sand bed.
Dryden Aqua has been using glass beads for water
filtration for the last 20 years. They make a good
filtration media for grossly contaminated water
because they are easy to back-wash and clean,
but this property makes it a poor filter media for
clean water applications such as swimming pools.
DRYDEN AQUA
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