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92-94 WATER TECHNOLOGY:SPN Master pages 15/1/09 16:50 Page 4
Lower chlorine levels will still improve
water quality says new Danish research
The case for using lower levels of chlorine “The experimental operation of the warm mg/l to 1.5 mg/l. Similarly, the levels of
in swimming pools has been boosted with water pool showed that it was possible to THM increased from 15-25 µg/l to a level
a new research paper from Denmark. achieve significant improvements in the around 40-50 µg/l at the higher content of
The paper, which is expected to be water quality with respect to chlorination by- free chlorine. Throughout the experiment,
available at the Swimming Pool & Spa products – and thus also improved indoor air the hygienic quality of the pool water was
International Conference in London in quality – in the pool facilities by operation at unchanged and remained within the
March, shows it is possible to achieve a lower content of free chlorine than are national standards at the new operating
significant improvements in the water used in the Danish swimming pools today. conditions with low chlorine content.
quality and improved indoor air quality – in “The content of combined chlorine rose Furthermore, the chlorine consumption
pools by using a lower content of free from a level around 0.2-0.35 mg/l to a level decreased by approx. 30% by lowering the
chlorine than is currently used in swimming around 0.35-0.65 mg/l when the free concentration of free chlorine of 1.5 mg/l
pools. The trial was carried out at the chlorine content was increased from 0.4 to 0.4 mg/l.“
Gladsaxe Sports centre in Denmark.
The trial was carried out by the DHI
Group (Danish Hydraulic Institute/Water
Quality Institute), and funded jointly by the
Danish Association for Swimming Pool
Technology and the Danish Environmental
Protection Agency.
In Denmark new regulations for the
operation of pool water facilities are Researchers at the University of Sheffield odours after the swim, changing a
expected to see a large number of Danish are to carry out tests to see if the smell person’s appearance, which contributes
public swimming pools change operational of a pool is linked to what consumers and to swimming being seen as ‘uncool’,
practice to lower chlorine levels. particularly women feel about the being bad for the skin and hair and
Researchers say that the latest trial at cleanliness of pool water. making a swimming occasion longer that
Gladsaxe Sport Centre will reduce the The research started before Christmas it needs to be because of attempting to
formation of chlorinated disinfection and the three month trial is likely to rid the body of the smell.
by-products significantly. produce results by early may. Over 1,000 Typical comments were as follows:
The paper adds: “The practice for operation swimmers in Sheffield and other parts of ‘Chlorine, really concentrated chlorine
of public swimming pools varies significantly Yorkshire will be interviewed to see if the goes up your nose and effects your head’
from a global as well as a European smell of chlorinated water is a concern. It ‘Apparently you get chlorine dandruff
perspective. Several European countries have will also revisit some of the conclusions in your hair and it does take a while to
a long tradition for operating swimming pools from a wider research into women and wash out. My hairdresser told me’
at lower pH and significantly lower content of swimming. ‘A swimming bath just smells of chlorine
free chlorine than the existing practice in Some years ago research by the doesn’t it? That’s what it smells of.’
Denmark, without any negative impact on the Women’s Sport Foundation and the
hygienic quality of pool water. The reason for Amateur Swimming Association found The Sheffield research plans to revisit the
this is that the proportion of the active species that instead of heightening feelings of 2002 research to look at wider issues in
for disinfection of chlorine (HOCl) is increased security with regard to health, chlorine terms of women’s perceptions to
by lowered pH and it is possible to lower the increased anxieties. swimming, their confidence to go
total free chlorine content without loss of Said spokesman for the research team: swimming in terms of body image and
disinfection capacity. The distribution of “We want to gain a deeper personal hygiene.
chlorine species as a function of pH shows that understanding of the issues surrounding Data from the General Household
the proportion of active component HOCl women’s participation in swimming. Survey were analysed to build up a
increases significantly when the pH is lowered, Woman are key for the research in that picture of women’s swimming and
for example from 7.3 to 6.7. It is thus possible they tend to introduce children to changes over time and to provide
to maintain the disinfection pressure at a swimming so there will be a female bias context to the study.
combined reduction of free chlorine and pH. to those we interview. Women also had very definite views
“The mechanisms for the formation of “Some research found that while the about hygiene in swimming pools. The
chlorinated disinfection by-products in smell of chlorine suggested cleanliness, it standards in swimming pools did not
pool water are very complex and still had the reverse effect. The smell of meet their expectations and managing
poorly understood, but there seems to be chlorine could make people think a pool these expectations remains an issue for
a consensus that the formation rate of is not clean or healthy.“ pool operators. Part of the problem was
chlorinated disinfection by-products is Previous research focused on women making pool users understand that they
expected to increase at higher between 25 and 34 years. are part of the process in maintaining
concentrations of chlorine. The smell of a pool was a concern and standards in pools. Respondents stated:
“Based on the chemistry of chlorine it was a major contributory reason to how There was a general feeling that
thus seems obvious to investigate whether a women who do not swim felt about the changing rooms are neglected and
change of the Danish practice for operating cleanliness of pools. Instead of the smell “put you off”.
swimming pools in the direction of lower of chlorine suggesting cleanliness, it had Other people’s (but not one’s own)
content of free chlorine, combined with the reverse effect. Instead of personal hygiene can be a problem –
lowered pH will lead to lower content of heightening feelings of security with e.g. ‘I’ve been there when there have
chlorinated disinfection by-products in pool regard to health, it increased anxieties. been shavings where someone has
water, thereby increasing the comfort and Chlorine is seen to impact on body been shaving their legs’. spn
reducing health nuisance for the bathers.
94 swimming pool news FEBRUARY 09 Digital edition available at
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