www.swimmingpoolnews.co.uk These organic pollutants react with the
chlorine to form combined chlorine, and one of these, trichloramine has a marked acrid odour. It is the main cause of red eye and is linked to elevated levels of asthma in children. Children’s pools are often shallow, warm with a high surface-to-volume ratio, and the water is frequently agitated by the use of fountains, and slides. All of these conditions encourage the formation and release of the trichloramine species, which can be removed using UV light. Adds Tony Leigh: “Traditionally chemicals such
as chlorine have been added to pools to provide effective disinfectants; this has worked well however organisms have started to develop resistance to chlorine, and several cannot be killed using chlorine alone. New developments in pool disinfection use electrolysis to form chlorine in situ by making the entire pool into a very low concentration brine solution. This seems to be a safer method of chlorinating the pool, and is gaining acceptance. A secondary issue for the pool operators are
the by-products formed by the addition of chlorine to pool water; combined chlorine species are irritants, cause corrosion and are increasingly linked by many research groups to asthma in children and elite athletes. UV light gained rapid prominence as an
effective disinfection technique, and was introduced into swimming pools in the UK in the mid 1990’s. Early attempts to use UV involved the combination of UV lamps and infra-red emitters; the UV was to disinfect the organisms in the pool water and the infra-red emitters destroyed the combined chlorine species. The lack of full flow capacity, and high cost led pool operators to move instead to ozone systems, which promised much. Ozone remained a preferred technique for several years, however high initial capital cost, coupled with ageing and complex plant requiring continuous attention led operators to think again about UV light. The arrival of powerful medium pressure lamps, capable of treating a full recirculating flow, coupled with automated wiping and lower overall operating costs led to the replacement of ozone by medium pressure UV systems. Today several thousand pools use UV as a method of disinfecting the “emerging” (chlorine resistant) organisms, and eliminating the combined chlorine nuisance. The UV market for larger swimming pools in
the UK is headed by Glasgow based Triogen (Degrémont Technologies–Triogen); Hanovia and atg UV Technology. Smaller residential pools have a wider selection of specialist suppliers who have all seen significant acceptance and approval of the system over the last five years. Triogen say there is now a clear and increasing
trend towards UV systems. “We are noticing that now if you have a municipal pool you need a UV system – that’s it. It is cheaper and it ticks all the
UVSystems FEB 2011 SPN
boxes,” said a spokesman. “It is better environmentally but the reason the system is being accepted without question is that it is effective against chlorine resistant micro- organisms such as cryptosporidium. It gives everyone the comfort they need.” Many people running larger pools still
misunderstood the relationship with chlorine and UV systems. Chlorine, the company stresses is still an important component of an UV system although lesser amounts were needed and the ‘side effects’ of bad odour round pools and eye infections were eliminated. Virtually no microorganisms
are immune to UV, even chlorine-resistant pathogens. Another major benefit of UV is that it significantly reduces the need for backwashing and dilution, saving hundreds of pounds a month for pool operators. atg believes the industry leap forward to UV is
driven by public demand for improved bathing environments and increased education and understanding on the benefit of a UV system. atg UV have warranted their success in the
leisure market to their breakthrough ECF system range, designed and engineered specifically for the swimming and leisure industry, catering for spa’s and diving pools to splash pads and full scale water theme parks. UV treatment is also used to break down
chloramines, resulting in a more pleasant and inviting leisure environment for customers, reducing ‘Red Eye’, skin irritations and the often overpowering chlorine smell associated with indoor swimming facilities. The elimination of chloramines also produces crystal clear, sparkling water, and vastly reduces the need for taxing shock treatments and backwashes. A typical UV system consists of a UV lamp in a protective quartz sleeve which is mounted within
45
ABOVE: Triogen’s UVARAY Medium Pressure UV Disinfection Systems are aimed at the commercial pool market
BELOW: A UV system from atg Technology consisting of a UV lamp in a protective quartz sleeve which is mounted in a cylindrical stainless steel chamber
a cylindrical stainless steel chamber. The water to be treated enters at one end and passes along the entire length of the chamber before exiting at the other end, receiving a dose of UV energy along the way. There are two main types of UV technology,
based on the type of UV lamps used: low pressure and medium pressure. Low pressure lamps have a monochromatic UV output (limited to a single wavelength at 254nm), while medium pressure lamps have a
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