When any type of
chlorine is added to water, it usually forms hypochlorous acid (HOCl
- the most powerful killing form of chlorine in water) and
hypochlorite ion (OCl-), a relatively weak form of
chlorine in water. The percentage of HOCl and OCl- is determined by
the pH of the water. As the pH goes up, less of the chlorine is in
the killing form and more of the chlorine is in the weaker form. The
total of HOCl and OCl- is the free available
chlorine.
Chlorine can combine with ammonia and nitrogen
compounds in the water to form chloramines, sometimes called
combined chlorine. By combining with ammonia and nitrogen, free
chlorine in the water is disabled. Chloramines are 60 to 80 times
less effective than free chlorine. Chloramines are formed any time
ammonia and nitrogen are in the water. Some of the ammonia and
nitrogen compounds are introduced into the water by swimmers and
bathers in the form of perspiration, urine, saliva, sputum and fecal
matter. An active swimmer sweats one pint per hour. The average
person sweats three pints per hour in a heated spa. Ammonia and
nitrogen compounds are also introduced into the water by rain. Each
drop of rain has some dissolved nitrogen from our atmosphere and
from automobile emissions.
Chloramines smell bad. This is the
smell most often associated with pools and spas in health clubs and
YMCAs. Chloramines are eye and skin irritants, and they cloud the
water.
Chloramines can be removed from the water by the
following three methods:
- By adding a
mega-dose of chlorine. Usually 3 to 6 times more chlorine than a
normal dose is added to the water, or the level of chlorine is
raised to 5 to 10 ppm and held there for 4 hours. This is called
superchlorination. To remove chloramines, the ratio of chlorine to
ammonia must be at least 7.6 to 1. If this ratio is not obtained,
then more chloramines will be produced. Swimmers and bathers
should not enter the water until the level of chlorine has dropped
to 3 ppm or less.
- By adding a
non-chlorine shock to the water. The most common chemical used for
this is potassium peroxymonosulfate. This ?shocking? requires the
addition of one pound of shock for each 10,000 gallons of pool
water.
- By adding ozone
to the water. If an ozone generator is installed on a pool or spa,
then oxidation of the ammonia and nitrogen compounds will take
place whenever the ozone system is operating. The longer the
system operates, the more the ozone can destroy the ammonia and
nitrogen. Although most ozone systems operate only when the pool
or spa pump is operating, there are 24-hour systems available
which will continously oxidize ammonia and nitrogen as they enter
the water.
Ozone oxidizes
soap, deodorant, hair spray, cologne, makeup, perfume, body lotion,
hand cream, sun tan lotion, saliva and urine. In addition, ozone
kills all pathogenic bacteria, germs and viruses. Ozone takes care
of the big job of oxidizing all these organic contaminants. Ozone
frees up the combined chlorine, thus leaving the chlorine free to
provide a residual. Ozone ultimately enhances the performance of
chlorine and bromine.
Less chlorine or bromine will be needed
to maintain a residual. Commonly, ozone reduces chlorine or bromine
use by 60-90 percent. The quality of water will be dramatically
better with the combination of ozone and chlorine or the combination
of ozone and bromine than with chlorine and bromine
alone.
