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AFM Filter Media
A disruptive technology for water treatment

By Dr. Howard Dryden

The two graphs represent the summary data analysis of verification tests conducted by IFTS, Institut de la Filtration et des Techniques séparatives, the leading independent accredited laboratory for the water industry in Europe and Asia. The data confirms that AFM is a disruptive technology that has the potential to transform the water industry.


Back-ground information, state of water treatment


More than 99% of the worlds drinking water filtration is by sand filter, the same technology is also used for the pre-treatment of water prior to membranes for desalination of seawater and for process water treatment by many industries including food and drink as well as the power sector. Sand filter media is a perfect substrate for growing bacteria, irrespective of how aggressive the media is air scoured and back- washed, it is impossible to remove the biofilm. If chlorine is used to disinfect sand, it simple promotes the growth of bacterium that produce copious quantities of alginate as a defense mechanism against the chlorine. The alginate glues the sand together and promotes biodynamic instability of the filter bed, and leads to transient worm-hole channeling of unfiltered water into the product water.

In temperate countries sand filters instability and breakthrough of solids (includes parasites, bacterium, other pathogens, heavy metals and priority chemicals) occurs approximately 0.1% of the run phase time. This may seem like a very high efficiency; however, one Cryptosporidium parasite will cause an infection. Drinking water accounts for approximately 5% of all infection in temperate countries, then there is the exposure to heavy metals and priority chemicals. In tropical countries, the high-water temperatures greatly increase the rate of bacterium division, sand filter instability is increased to 4%, and the level of infection is increased to as high as 80%. In Europe, the BACS ozone / biologically activated carbon system is being used on many water sources, when the system is working properly it provides excellent water quality. However, the ozone can genetically change bacterium, and alter complex organic molecules, the activated carbon absorbs the molecules and acts as a substrate for growing bacteria. The system can generate genetically modified bacteria and manufacture antibiotics and other toxic chemicals which are then discharge them into the drinking water network.

Water treatment therefore has the potential to make water much worse than the raw untreated water, another example is the chloramination of water to prevent THM formation. The process of choramination is now practiced in at least 25% of all the water supplies in Europe and up to 50% in the USA. Monochloramine formed by the process is said to be nontoxic, however it instantly changed to trichloramine under acidic conditions in your digestive system, and trichloramine is extremely toxic. The instability of the sand filters also allows aluminium based flocculants into the product water, or polyamines that may contain acrylic, these chemicals are also toxic and carcinogenic.

There is clearly a great deal that needs to be done to improve the quality of our drinking water. 30 years of R&D by Dryden Aqua has resulted AFM grade 0 AFM which is arguably the best water filtration media available to the water industry. AFM grade 0 has been verified by IFTS in France to remove >99.9% of 4 micron particles at a water flow of 5m/hr. The smallest know human parasite is Cryptosporidium at 4.5 to 5 um. AFM does not biofoul, the media is stable and it will never allow unfiltered water to enter the product water. AFM grade 0 is verified by IFTS to be more than 100 times more effective than 16 x 30 sand at removing sub 4 micron particles.

AFM can be used in any sand filter system for drinking water, waste water treatment of for the pre-treatment of water prior to membranes. It is a simple retrofit, by replacing the sand with AFM, the performance of any water treatment facility will be greatly improved. In addition, there will be a reduction in the oxidation demand of the water which will negate or reduce the requirement to use coagulants and flocculants. The return in capital out of revenue savings will be under 3 years, and in many cases, can be as short as 1 year.

AFM is manufactured under ISO9001-2008 standards, certified under NSF61 and DWI Reg 31 by WRC, food grade approval HACCP and verified by IFTS. We have been manufacturing AFM for almost 30 years, and produce sufficient to provide clean water for more than 50 million people every year. Dryden Aqua is the leading filter media manufacturing company in Europe, backed-up by 30 years of research to provide the best possible water quality, reduce risk and save money.

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