Case study - UV systems for spas & hydro pools

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Courtesy of atg UV Technology

With the rise of health centres and leisure clubs throughout the UK, a key feature in many modern facilities is the inclusion of spas and hydro pools.  As a specialist aquatic application, spas and hydro pools feature high turnover rates, high bather loads, increased turbulence and water temperatures above 35oC.  This combination of factors provides a perfect breeding ground for harmful microorganisms such as E-Coli, Legionella and chlorine resistant strains such as Cryptosporidium and Giardia, significantly increasing the risk to bathers.         

As a result many leading leisure operators, health clubs, aquatic facilities and hotel chains have adopted UV disinfection systems to control this risk.  UV Systems offers 3 main benefits: -

Improves Health and Safety

UV is a highly effective disinfection technology used widely in drinking water.  A correctly sized medium pressure UV treatment system will allow operators to reduce their residual chlorine levels down to as little as 0.5 ppm. Even the 17 known chlorine-resistant pathogenic microorganisms such as Cryptosporidium and Giardia are easily treated with UV.

Reduces Harmful Chloramines

Chloramines are the unpleasant chemical formations created when chlorine combines with the nitrogenous compounds introduced to the pool by bathers. Chloramines are powerful irritants which are responsible for eye, skin, respiratory complaints and the unpleasant ‘chlorine smell’ commonly associated with indoor pools. Chloramines are also corrosive and can lead to the damage of pool buildings and structures, through stress corrosion cracking.

Improves Water Quality

Medium pressure UV systems initiate photo-oxidation reactions which remove unwanted organic contaminants, resulting in crystal clear, sparkling water. This occurs both by direct photolysis and through the production of hydroxyl radicals, a highly reactive chemical species which oxidises and breaks down organic compounds and contaminants. These reactions lower the organic loading of the water and significantly improve its clarity and quality.

UV Systems for Spas & Hydro Pools

UV manufacturers now offer a specialist range of UV systems tailored to meet the requirements of spas and hydro pools. UV systems for this application are sized to treat flow rates of 10 – 50 m3/hr, and typically feature a single lamp design, using polychromatic medium pressure UV lamps.  It is important to note that monochromatic ‘low pressure amalgam’ UV lamps should not be used for aquatic applications, as they lack the ability to operate of elevated water temperatures, and do not provide the necessary UV output to improve water quality, and reduced problem chloramines.   

In order to accommodate the reduced installation space often associated with aquatic plant rooms, manufacturers such as atg UV Technology in the UK, and ETS in the U.S.A. now offer in-line UV systems in 3”, 4”, 5” and 6” versions, designed to install directly into the pipework. In addition to their smaller foot print and easier installation, the inline design provides greater hydraulic and treatment efficiency than standard S shape UV systems, lowering both capital and operational costs.   

UV Specifications

UV systems should include: 316L stainless steel chambers, UV intensity monitoring, automatic wiper systems, strainer baskets, fully variable power for energy savings during periods of no/low use.  UV manufactures should always follow best practise when sizing a UV system, ensuring to supply UV equipment capable of providing a 60 mJ/cm2 dose (average) at a UVT (UV Transmittance) of 94%.

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