AFM is an Activated filter media, a report by Jimmy Lamb from Pollet Group
Before Pollet Pool Group became the UK distributor for the original Activated Filter Media (AFM), I was just as sceptical as the next man about what ‘Activated’ actually means. Is this something that has simply been thought up in a marketing meeting?.
With an open mind and having taken the time to listen to those who are qualified, experienced and have knowledge and science facts behind it, I’m now a convert.
Let’s start with what we are trying to achieve. To provide safe, algae free, sparkling clear and inviting pool water. We dose a disinfectant (usually chlorine) to kill bacteria that are introduced to the water mainly by bathers. Disinfection is a lot different to sterilisation. The definition of Sterile is, ‘free from bacteria or other microorganisms’ whereas in swimming pool water we will always have bacteria present. It can take up to 30 seconds for free chlorine to kill bacteria. Some micro-organisms take a lot longer or are even resistant to high levels of free chlorine, not to mention the fact that chlorine has a dependency for its efficacy governed by the pH value. The higher the pH, the less effective is the free chlorine.
Have a think; where do you think the largest surface area is in a swimming pool? The pipe work? The pool tank itself? What about the filter? Consider, not just the filter vessel but, each and every grain of sand media inside the filter has a surface area. In fact the filter media equates to more than 90% of the entire pool surface area. Any surface the pool water comes into contact with, bacteria will try to adhere to. Although sand has been a very effective filter media, it does have drawbacks. Sand offers the perfect surface for bacteria to adhere itself to and secrete an alginate to protect itself from the chlorine. This alginate, in time becomes a biofilm, a haven cryposoridium to hide, andf for o bacteria to grow, and will increases chlorine consumption and, in-turn create more combined chlorine (chloramines). In a typical domestic installation it is likely that the pool circulation pump is single speed. Although there will be less resistance, this means the near same velocity of water passes through the filter in a backwash cycle as when in normal filtration. It is therefore unlikely that adequate fluidisation of the sand filter bed is achieved to help release all the dirt that has accumulated since the last backwash. Let’s face it, pool owners across the country neither backwash often enough, nor for long enough.
The accumulation of dirt in a filter with a poor backwash flowrate will further encourage bacteria growth and exacerbate the biofilm problem. One solution to this is to install a multispeed pump so that the flow can be increased to really achieve the desired fluidisation. A backwash really should take place once a week and for between 3-5 minutes. It could be said that by swapping the sand media for a recycled glass could overcome the lack of fluidity during a backwash. This is mainly due to the glass not being as dense as sand but, any old recycled glass media like sand, will not prevent bacteria adhering to the grains and in time a biofilm will become established. Once the alginate slime is already attached to the sand or glass grains it has probably caused clumping of the media and in-turn, channelling that leads to poor filtration.
The introduction of a so called ‘Activated Filter Media’ (AFM) into the UK swimming pool market some years ago created quite a stir. Not just with other filter media suppliers but, with manufacturers of the filters themselves. The thought of putting glass anywhere near a pool was a no no, let alone in the filter. What might happen if the laterals were to break and the glass end up in the pool? Surely we’d have cut feet all over the place? This was just one of the objections.
The brains behind such technology have spent years developing this technology and have approached pool water treatment from a biological perspective rather than what we have done since year dot and tackled pool water treatment with chemistry! The formation of biofilm and associated problems is a biological problem, not a chemistry problem and so therefore requires a biological solution. AFM is a bio-resistant filter media that bacteria cannot adhere to, thus eliminating the potential formation of biofilm in the filter media .
Different glass colours have different physical and chemical properties. It is green glass that has the appropriate balance of these properties. This glass is sized and shaped to give it the correct mechanical performance but, it also undergoes a 3 stage process including heating the glass to near melting point. This process has a dramatic effect on the surface of the glass and increases the surface area by 300 times. With the enhanced chemical properties and increased surface area through the activation process this media now has huge adsorption to attract heavy metals and organic molecules. This media has outperformed both sand and ordinary glass media in independent tests carried out by the well recognised IFTS (Institut de la Filtration et des Techniques Separatives). IFTS is recognised as the leading independent accredited laboratories in Europe for all water industry specialising in water filtration media.
Littlehampton Leisure Pool on the South Coast is one of few large commercial pools that have been enjoying the benefits of AFM as their preferred filter media in conjunction with the complete DAISY (Dryden Aqua Integrated System). This installation replaced a very expensive to operate and maintain Ozone system. As a result, Littlehampton has the best water quality that I have ever seen in a busy commercial leisure pool and I’ve visited many commercial pools in my time!. They have very little chlorine smell in the pool hall and are yet able to keep free chlorine levels as low as 0.7mg/l. Not only do they have superior water quality but they are making significant saving on their running costs.
The primary focus of Dryden Aqua and the AFM DAISY is to provide clean safe water & air for the public, especially children. A healthy environment for pool staff and to give pool operators a return in capital out of revenue savings by conserving on water, energy and chemicals.
AFM has been adopted throughout Europe by some of the largest swimming pools such as Svømmestadion Danmark in Denmark. At Dryden Aqua, they have the capacity to process 50% of all the green glass bottles in Scotland and can manufacture sufficient media for the entire water industry in the UK.