Swimming Pool Water Disinfection;
Why the Use of Strong Chemicals is Currently
Unavoidable in the disinfection of Pool Water
Many people are or believe they are allergic to chlorine and want a swimming
pool that does not rely on it to disinfect the water. Unfortunately this
is not possible at the present time because there is no other form of water
treatment that is guaranteed to be safe. Probably every healthy pool in
the world uses either Chlorine, Bromine or Peroxide and this article explains
why that is the case.
All three of these chemicals work in the same way and all have the same
drawback that you are swimming in a chemical soup!
Dreadful Diseases than can occur
Swimming pool water contains bacteria that can cause many types of dreadful
diseases in humans. The bacteria that cause these diseases are known as
pathogenic bacteria and the pool water disinfection process must kill
these for the pool to be safe to swim in.
The disinfection of Water in the past has always relied on Chlorine because
it is a very efficient sanitizer and has always been relatively cheap.
However it is getting more expensive and there are a few doubts about
its absolute safety when people are exposed to it over a long term. Because
of this plenty of research has been carried out to find other methods
of cheap, reliable water treatment that will kill the pathogens.
What are the Alternative Disinfectants to Chlorine or Bromine?
Ultraviolet Light
The water disinfection properties of ultraviolet light were discovered
over 100 years ago. The light must be at a specific wavelength and power
to treat the water as it passes through a treatment cell. The UV light
causes biological changes that kill the pathogens and significantly reduce
the concentration of bacteria in the water, without leaving any dangerous
by-products.
However the water must be totally transparent without any turbidity for
the UV light to be totally effective (Turbidity is a measure of how transparent
water is and increases due to the presence of particles in the water).
It is also very difficult to measure how effective the UV light treatment
is. With Chlorine this is easy because the water is treated with sufficient
chemical to make sure that there is enough residual chlorine to ensure
that the pool water is safe.
So the UV treatment needs a filter to ensure that the water is never cloudy,
but this filter will also harbour a seething mass of bacteria (See other
article on Swimming Pool Water Quality).
The result of all this is that UV can be used to reduce the amount of
chemicals used but every pool will still need a residual level of chlorine
in the water for it to be 100% safe.
Ozone
Ozone is generated when a molecule of oxygen is illuminated by high energy
ultraviolet light. It is formed when three atoms of oxygen are bound together
instead of the normal two. The extra oxygen atom makes ozone a highly
energetic oxidiser and very efficient pathogen killer.
It is produced for swimming pool water using two different methods. In
the UV method, air is passed over a UV bulb, and the radiation creates
nascent oxygen and then ozone. In the corona discharge method, a small
lightning storm is created in an air filled chamber.
Ozone is a powerful sanitizer, but it is a gas.
Its primary drawback is that it quickly reverts back to oxygen and so
it is currently impossible to ensure that all the water in a pool has
been treated. The short life span of ozone and the difficulty of ensuring
even distribution throughout the water that is being treated results in
a requirement for a low residual level of chlorine as in UV light sanitation.
However the actual chlorine usage is reduced by about 80% and there is
no doubt that ozone sanitation use will continue to increase in the pool
industry. It gives water a better smell, taste and clarity than chlorine
alone, and it produces no by-products.
Ozone also removes certain dissolved metals and rids the pool of soaps,
scum, oils and chloramines.
It is probably the pool water sanitation system
of the future
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