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64-65 UV:SPN Master pages 18/5/09 19:41 Page 3
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“TODAY SEVERAL THOUSAND POOLS USE UV AS A
METHOD OF DISINFECTING THE ‘EMERGING’ CHLORINE
RESISTANT ORGANISMS, AND EFFECTIVELY ELIMINATING
THE COMBINED CHLORINE NUISANCE”
“A secondary issue for the pool swim team by the 2000 Olympics in Australia. of food. Without this ability the organism
operators are the by-products formed by Thickett in 2002 investigated the effects quickly dies.
the addition of chlorine to pool water; that breathing chloramines has on indoor “A number of researchers have now shown
combined chlorine species are irritants, pool workers, and noted that the pool that organisms exposed to a comparable
cause corrosion and are increasingly liked workers asthma symptoms resolved dose of UV light from a low pressure lamp are
by many research groups to asthma in significantly when placed away from the able to repair the damage to their DNA, a
children and elite athletes. pool environment. phenomena called photorepair. Two repair
In 2008 Bernard published research mechanisms have been observed; light repair
The risk of infection findings from a study of chloramine (triggered by enzymatic stimulation) and a
“People swimming in pools, using splash exposure from outdoor pools, concluding slower dark repair. The light repair process
pads for recreation, or visiting indoor or that there is a marked increase in asthma uses an enzyme called photolyse to repair the
outdoor water parks are at risk from caused by attending outdoor pools. damaged DNA. Photolyse is stimulated by
waterborne infection. Some of these Outdoor pools were thought not to be a sunlight, and this explains why medium
infections are naturally present on skin, in source of chloramine irritation, and in 2009 pressure systems are usually selected for
hair, noses, mouths, intestinal and uro- a study of epithelial damage in elite open air water parks, where water will be
genital tracts. The vector for transmission is athletes was published by Carlson et al. exposed to sunlight after disinfection, and
both the water and pool surfaces. The Likewise Bougault studied asthma, also for waste water reclaim applications,
adoption of UV light should not be seen airway irritation and epithelial damage in where highly polished wastewater is stored
either to replace the dosing of chlorine, or swimmers and observed airway hyper- underground as part of an Aquifer Storage
indeed to replace good pool hygiene responsiveness in 69% of swimmers. and Recovery process.
practices. The UV systems serve a dual Other effects of chloramines can include No organism is able to develop
role; primary disinfection of the waterborne corrosion of the pool structure. The volatile resistance to UV light, and the market
organisms, and effective photolysis of the chloramines carry chlorine species to leading companies such as ETS, LLC, atg
combined chlorine species. condensation in parts of the building remote UV and Trojan Technologies have now
“Pseudomonas aeruginosa is probably the from the pool. Repeated evaporation causes compiled databases to quantify what level
most common of pool organisms. This these species to concentrate, causing both of exposure to UV light is required to
species is demonstrating increased resistance safety critical damage and area degradation. achieve a predictable level of deactivation.
to chlorine, particularly in spas or hot tubs. Stress corrosion cracking of roof supports, System sizing is a function of determining
“Some of the protozoan pathogens such wire suspensions and bolt heads can lead to three variables; flow rate, what organisms
as Cryptosporidium and Giardia have catastrophic failure. are likely and the transmittance of the water.
developed complete resistance to chlorine. “Air treatment systems can play a role in Several factors can effect the transmittance
They are excreted by infected swimmers reducing the transit of the chloramine of the water, including turbidity, suspended
during fecal events, and a carrier state species, however this approach is not a solids and color. Variations in these
exists where those infected show no root cause solution. parameters are undesirable for recreational
obvious symptoms. “Chloramines are linked to pin hole water. Several UV companies have
“Other protozoans include Naegleria failure of copper pipe, however the undertaken system validation using non
Fowleri, which is a pathogenic amoeba that phenomena is site specific. pathogenic surrogates to verify actual
causes the fatal disease primary amoebic performance using a third party test house,
meningo-encephaltis. The organism enters The role played by UV light and to understand properly the capacity of
the human brain through pool water “UV systems are used to both disinfect the the machines. New York state requires that
inhaled through the nose. Several viral pool water, and also to break up or all UV systems are independently validated
species are isolated from swimming pools, photolyse the combined chlorine species. in accordance with strict protocols.
and Enterovirus is often found in wading Most of the systems in use in pools
pools. This species causes gastroenteritis. globally are medium pressure systems, as Photolysis
this type of lamp produces many different In the same way that specific UV
Eliminating combined UV wavelengths, and hence are sometimes wavelengths are absorbed by DNA,
chlorine called polychromatic lamps. Low pressure leading to bonds rupturing, so other
“The strong, acrid chlorine smell lamps are sometimes referred to as specific wavelengths are absorbed by
associated with swimming pools and spas monochromatic lamps as they produce a mono, di and tri chloramine. When these
is the combination of chlorine with single UV wavelength at 254nm. wavelengths are absorbed, the energy they
compounds introduced into the pool , carry breaks the chemical bond, and a
often by bathers themselves. Bathers Disinfection breakdown process is initiated.
introduce urine, sweat, hair, suntan oil and “UV light has the ability to destroy the Medium pressure lamps produce these
other organic compounds into the pool. cross bonds in the DNA contained in the wavelengths in abundance, however as low
These react with the chlorine to form nucleus of an organism (or RNA in the case pressure lamps only produce a single UV
nitrogen trichloride, chloramines, of a virus). UV light between the line at 254nm, they are not well suited to
trihalomethanes, chloroform, halogenated wavelengths 230nm to 300nm are use for the specific removal of the nuisance
hydrocarbons and aldehydes. absorbed by DNA, and this energy causes chloramine species.
“Many research groups have studied the the cross bond to rupture. This process is Operators also report improvements in
effect that exposure to these chemicals has, called dimerization. Technically the water clarity, when the UV system is in use.
for a wide range of target groups. 11% of organism is not killed by the UV light, Most pools turn the UV off or reduce output
swimmers at the 1984 Olympic games rather the damage caused to the DNA overnight when the chloramine challenge is
recorded some degree of asthma rising to denies the basic cell function of absent, and start the system in advance of
>20% by 1996, and 25% of the US Olympic replication, respiration and the assimilation the pool opening in the morning. spn
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JUNE 09 swimming pool news 65
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