For this reason, high efficiency filters to keep the water of pools or spas clean and clear are a must.
As the media of choice in cartridge-based pool filter systems, nonwovens have a vital role to play – as will be demonstrated at INDEX 11 – the leading nonwovens exhibition which takes place at Palexpo in Geneva, Switzerland, from April 12-15 2011.
Fastest growing
According to EDANA, the European-headquartered industry association which sponsors the INDEX event, filtration is one of the fastest growing segments for the nonwovens industry.
The $45 billion filtration sector is characterised by dozens of end-use areas and applications, and nonwoven media can be engineered precisely to meet exacting specifications and stringent regulatory requirements for the filtering of air, dust and liquids, to fine chemicals, gases and bacteria.
What’s more, nonwoven nanofibre filtration media is now filling the micro-filtration performance gap that had existed in the past, offering benefits such as enhanced air quality, reduced energy costs and longer service life, while treatments such as nanocoating with plasma are providing the opportunity for media made of cheaper fibres such as polyester, cellulose and nylon to replace highly resistant and rigid polymers polymers such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE).
Such expensive polymers have been necessary in the past where filters were intended for repeated use in many industrial settings, since it is vitally important that the integrity and consistency of pore size is retained throughout a product’s lifetime, despite the often harsh environments they are exposed to, including cleaning processes.
As far as specific end-use areas are concerned, there are more than fifty filters in an average passenger car, contributing to functions ranging from the engine’s performance and oil and fuel consumption through to the quality of the air in the cabin.
For general air filtration, nonwoven filter media are to be found in industrial heating, ventilation and air conditioning (HVAC) systems as well as in consumer products ranging from vacuum cleaners and cooker hoods to PCs. Liquid filtration systems based on nonwovens are widely used in the food and beverage, water, medical and hydraulics industries, while speciality uses extend to antimicrobial and biopharmaceutical applications.
Pool sanitation
Meanwhile, there are estimated to be around 2.5 million privately-owned swimming pools in Europe, in addition to hundreds of thousands of public swimming pools, saunas and spas in hotels and leisure facilities.
Their proper sanitation is necessary, to maintain the visual clarity of the water, and prevent the transmission of infectious diseases.
In addition to filtration, sanitation and regular testing of the water, including the chlorine and pH levels, removes infectious micro-organisms, ensuring swimmer hygiene to minimise the introduction of contaminants into the pool.
The World Health Organisation has published international guidelines for the safety of swimming pools and similar recreational-water environments, including standards for minimising microbial and chemical hazards, while the US Centers for Disease Control and Prevention (CDC) also provide information on pool sanitation and water related illnesses.
Avoiding hot tub rash
The CDC has reported that Americans are increasingly getting sick from public swimming pools and spas. In 22,000 inspections it conducted as part of a survey, one or more pool safety violations ranging from filtration to chlorine problems were discovered in 54% of them.
Improperly treated and filtered pools and spas can be the source of a range of water-borne illnesses, including Giardia, E. coli, shigella, cryptosporidium and pseudomonas aeruginosa (hot tub rash).
In private pool filtration systems, an electrically-operated water pump is the prime motivator in recirculating the water from the pool. When run at intervals, it forces the water through the filter and then returns it to the pool. Commercial and public pool pumps usually run 24 hours a day.
A pressure-fed filter is typically placed in line immediately after the water pump and traditionally, the filter media has been sand – sifted through a fine brass-wire mesh. The sand in the filter will typically last five to seven years before all its microscopic ‘rough edges’ are worn off and it gradually becomes more tightly packed and no longer works as intended.
Other filters use diatomaceous earth to help filter out contaminants. Commonly referred to as DE filters, they will trap water-borne contaminants as small as 1 micrometer in size.
DE filters, however, are now banned in some US states, since they must be emptied out periodically and the contaminated media is often flushed down the sewer, causing problems.
Increasingly, the use of cartridge filters is coming to predominance, as a result of the convenience they offer pool and spa owners compared to sand or DE filters.
A recent US study found that 42% of pool-builders nationwide rank cartridges as their number one filter preference.
Recently-introduced nonwoven filter media innovations include pleatable polyester types, which provide pool and spa owners with more balanced overall performance, as well as antimicrobial versions which inhibit bacterial growth.
Advanced nonwoven web-forming and hydroentangling techniques, along with highly developed finishing, provide superior uniformity and tightly controlled pore sizes in the media.
Leading spunbond nonwoven fabrics, meanwhile, can guarantee filtration efficiency for 30 years and have easy-to-clean surfaces.
Often, a nonwoven material’s construction and fibre orientation allow water to circulate more freely through the filter cartridge than in other media designs, enhancing the filtration process and reducing strain on pump motors.
Such products will be widely displayed at INDEX11.
