Super Chlorinating
Shock Treating/ Super Chlorinating
"Burning up the pollutants with strong oxidizing chemicals"
Shock treating or shocking refers to the addition of anything to the
water that will remove or destroy ammonia and nitrogen compounds by
oxidation - traditionally this has been chlorine. There are now some non-chlorine
shock products.
Organic matter and ammonia compounds enter a swimming pool or spa from
many sources. Swimmers and bathers are major contributors with their
bodies giving off saliva, sweat, urine and faecal matter. Windblown dust,
fertilisers, algae, leaves, twigs, certain water-treatment chemicals and
rain introduce contaminants into the water.
Chlorine and bromine combine with ammonia and nitrogen compounds to
form amines. Chloramines smell bad, they are eye and body irritants and
they are also poor disinfectants. Bromamines do not have an odour problem
and are as effective as free bromine for disinfection. Organic wastes
build up and become sources of irritation.
Dealing with the problem of combined chlorine requires testing the
water to see how much of the chlorine in the water is free and how much is
combined. The commonly used OTO test will not perform this task. It can
only tell you the total chlorine level and can't differentiate between
free and combined chlorine. However, a DPD test kit or a syringaldazine
test strip will do the job.
Chlorine Reacts with Ammonia to remove it.
When chlorine is introduced into swimming pool or spa water it forms
hypochlorous acid (HOCl (free chlorine)) which dissociates into H+
and OCl-, the degree of dissociation depends upon the pH. The
OCl- is a strong oxidiser and will oxidise the ammonia to form
a combined chlorine compound known as monochloramine (NH2Cl)
and OH-. More chlorine as OCl- is required to
continue the oxidation of the nitrogen or ammonia. If no more chlorine was
in the pool or added to it, the pool or spa water would have a large
amount of combined chlorine as monochloramine rather than the desired free
chlorine.
As more chlorine is added, the monochloramine is now oxidised by the
additional chlorine as OCl- to form dichloramine (NHCl2
+ another OH-). The dichloramine is again oxidised by OCl-
to form trichloramine (NCl3 + another OH-). The
trichloramine is unstable and breaks down to simple nitrogen and chlorine
completing breakpoint chlorination.
Superchlorination to truly achieve the destruction of all organic waste
can be very tricky. If not enough chlorine is added, the combined
chlorine problem is only made worse. When this happens, eye burn and
skin irritation are raised to very high and very irritating levels. If too
much chlorine is added, it may take days to drop to safe levels (less than
5 ppM) before bathing can be resumed.
It takes 7.6 parts by weight of chlorine to oxidise 1 part of ammonia.
Other organics or products in the water will also consume some of the
added chlorine so that 7.6 parts is not enough. 10 parts of chlorine for
each part of ammonia is generally the required amount. Dirty and
contaminated pools could take up to 25 parts or more of chlorine. As a
general rule of thumb, the addition of 10 times the combined chlorine
level will achieve breakpoint. In other words, if the water has 0.5ppm of
combined chlorine by test, you will need to add 5 ppM or more of chlorine.
Each of the popular chlorine products provide a different amount of
available chlorine when added to water. In a typical 100,000 litre pool it
will take about 1 kg of available chlorine to achieve 10 parts per
million.
Non-Chlorine Shock
The active ingredient in these non-chlorine shock products is potassium
peroxymonosulfate, also known as permonosulfate. Like chlorine,
permonosulfate is an oxidiser that will destroy organic contaminants such
as ammonia in swimming pools and spas. However, permonosulfate compounds
do not kill or disinfect they simply control organics and combined
chlorine, helping assure that the chlorine can do its job as a sanitiser.
Permonosulfates oxidise by using the element from which oxidation derives
its name -- oxygen. Oxygen is a pure form of oxidiser. Unlike
superchlorination which is used to destroy problems such as odours, eye
and skin irritation after they occur -- Permonosulfates are effective in
preventing these problems because Permonosulfates do not contain chlorine,
but rather oxidise waste through the use of oxygen, they do not go through
the various stages of chloramine formation to achieve breakpoint. Instead,
they react directly with the ammonia to produce chloride and nitrogen. No
matter how little of the non-chlorine shock you add, at least some of the
organic contaminants will be destroyed, and no additional chloramines will
be formed. This overcomes one major drawback of superchlorination. And if
you overdose with a non-chlorine shock by adding more than is required, no
extended waiting period is needed before swimming can be resumed. Although
bathers should not be present when any chemical is added to the water,
swimming can be resumed after the permonosulfate has had a chance to
dissipate, usually just a few minutes. In fact, the excess chemical will
remain in the water, ready to destroy any contaminants that may enter the
pool from bather waste and other sources.
Permonosulfates are 100-percent soluble and will not leave a residue or
bleach vinyl liners or swimming suits. Because they are chlorine-based, it
is not necessary to calculate how much to add to beat a given chloramine
problem. Permonosulfates help prevent chloramines from forming, so
whatever quantity is applied will have some positive result. Unlike
superchlorination, which requires you to figure out how much chlorine to
add and how often to correct problems, Permonosulfates, are generally
added at the rate of 0.5 kg per 35,000 litres on a regular, weekly basis.
Permonosulfates effectively control the formation of chloramines, which
cause odours, reduce disinfection and cause eye and skin irritation.
Permonosulfates cause an acidic condition to occur i.e. they have a low pH
of about 2.3 to 3, so steps will need to be taken to counteract the acidic
condition that may be caused by using them. Permonosulfates do not add to
the calcium or other undesirable solids or Cyanuric acid in the water.
Also, no special handling is required, and there is no reason to close the
pool or spa or to restrict swimming due to excessive chlorine residuals.
Finally. there is no need to calculate how much to add in order to be
effective.
Permonosulfates are also safer to store and handle than chlorine
products, because they will not burn or release chlorine gas.
Copyright © 1996, 1997, 2002 TPS Pty Ltd
