Discussion of Chlorine & Hydrogen Peroxide (Oxygen Shock)
Article 1: Oxygen Shock:
Article 2: H2O2: Advantages
alternative methods are gaining in popularity and acceptance, chlorine remains
far and away the No. 1 sanitizer used in pools and spas.
time-tested ability to quickly kill nearly every microorganism that can cause
disease is well known, disinfecting pool and spa water by killing pathogenic
bacteria and viruses within seconds of application.
addition to its sanitizing capabilities, chlorine is also widely used as an
oxidizer, helping to rid the water of contamination that can be introduced from
a variety of sources. These are generally recognized as bather wastes like urine
and perspiration, cosmetic products, sunscreens and lotion. But they also
include organic contaminants that can be introduced through wind and rain, such
as dust, dirt, pollen, insects, plant and grass debris and airborne pollutants.
sanitizer works hard at oxidizing — or burning up — these contaminants, but
as they build up in the pool water, they combine with the sanitizer in the water
to produce what we call chloramines or bromamines.
the case of chloramines, they can cause a foul smell and can lead to cloudy,
dull water. While still a killing forn of sanitizer, the effectiveness of this
combined form of chlorine is minimized and, if left unattended, can lead to
poorer and poorer water quality and algae headaches.
of the problems that occurs automatically is that when these contaminants are
introduced into the water, the sanitizer — which should be working on killing
bacteria and virus — shifts and tries to do its secondary job as an oxidizer.
Chemically, we say that there is a sanitizer demand.
as the sanitizer is called upon to oxidize to destroy organic contaminants, its
efficiency as a disinfectant is significantly reduced.
overcome the buildup of the combined forms of sanitizer, the industry standard
has been to superchlorinate or shock the water. In this process, the chlorine
level is raised to about 10 times the normal readings on a chemical test to
reach what is, called breakpoint.
this point, the chloramines are broken down, bringing the chlorine back to its
free — and best killing form.
is common, however, for a small amount of combined chlorine to remain in the
water after a corrective breakpoint has been reached, especially when organic
nitrogen compounds are present in the pool water. Also — in the real world —
chlorine will continue to combine with contaminants that constantly enter the
water, and almost immediately again begin forming chloramines. So realistically,
you can never totally rid the water of chloramines.
common problem, of course, is finding the proper level of chlorine you must add
to reach this breakpoint. As you add chlorine, you are effectively raising he
chloramine level even higher and higher in the pool. And if you fail to reach
breakpoint, you are simply increasing the undesirable effects.
high chlorine levels in the pool can cause significant down time while normal
levels are returned, or you may need to revisit the pool to dechlorinate.
a pool pro to do?
way that pool operators are be ginning to overcome the problem is through use of
a non-chlorine shock — most notably potassium monopersulfate — to shock
their pools. And rather than waiting for combined chlorine readings to rise
above proper levels, they are using monopersulfates on a regular basis as a
preventative measure to oxidize contaminants before they combine to cause water
addition to potassium monopersulfate, other oxygen-based shocking chemicals
could include sodium persulfate, sodium carbonate peroxyhydrate (also known as
sodium percarbonate) and hydrogen peroxide. Sodium persulfate has about the same
active oxygen content as potassium monopersulfate, but has a low reactivity and
also can cause a chemical buildup in indoor pools. The other two have high
active oxygen content and are commonly used in dechlorination.
advantages to oxidation without chlorine include that fact that there is no
added production of chloramines and sanitizer efficiency is increased without
raising the chlorine level. The chlorine ˙ without its added duty as an
oxidizer — is free to do its job as a bacteria killer. At the same time,
monopersulfates accelerate chloramine degradation.
regular, preventative use, you end up with better water quality, longer periods
of uninterrupted swim time, and a more manageable maintenance schedule.
monopersulfate is a strong, odorless, oxygen-based oxidizer that works well with
sanitized chlorine, bromine and most alternatives. Unaffected by UV degradation,
non-chlorine shock can be added to pool water day or night, and swimming can
resume after just a short waiting period.
product is fast dissolving, and when broadcast uniformly over the water with the
circulation system running, it will quickly mix into solution with the pool
water. Because of its characteristics, monopersulfates will not damage or fade
doses are one pound per 10,000 gallons of pool water, but more frequent and
higher doses may be useful in commercial pool applications. In spas,
manufacturers recommend oxidizing with non-chlorine shock after each use.
Recommended dosage for spas is 1-2 ounces per 250 gallons.
the manufacturer of potassium monopersulfate, recommends its use on a regular
basis rather than waiting for problems to occur. Their reasoning is simple: If
the condition of your pool water is so bad that it needs shocking, something has
already gone amiss. And you don't have to be a chemist to know that it makes
more sense to prevent a problem in the first place that it does to try to fix
one once it has occurred.
rationale of using this preventative medicine for your customers' pools is a
strong one. When the quality of water deteriorates to such a degree that
shocking becomes necessary, are you really sure that you are providing enough
during the time you are superchlorinating, your pools may be unusable, which can
be especially troublesome in commercial pools. In addition, the work associated
with corrective action can be significantly more time consuming than the few
minutes added to your routine maintenance schedule to add non-chlorine shock on
a regular basis.
winterizing using a non-chlorine shock can help to prolong the sanitizer
residual, which can be a benefit as the pool remains idle for several months on
end. The shock treatment accomplishes this by oxidizing wastes and thus
"freeing up" the chlorine or bromine to do its job as a disinfectant.
Potassium monopersulfate does not, however, kill bacteria and cannot replace
your choice of sanitized. And because of its acidic nature, regular use will
also lower pH and total alkalinity. Soda ash or bicarbonate should be added to
maintain acceptable levels of pH and alkalinity.
testing, you should be aware that while no interference will be detected when
using OTO test kits, there is minimal interference with free chlorine readings
on DPD tests. The DPD reacts with the potassium in the total chlorine test to
give a false high combined chlorine reading, but there are test kits available
to eliminate monopersulfate interference.
using test strips, service professional should be aware that while there is no
interference with free chlorine readings, the potassium can react with total
chlorine and total bromine tests.
compounds — even when used on a regular basis as part of a prevention program
— are not a cure all for water problems. Naturally, you still need to
consider: Circulation — your pumps and filters should be properly sized for
adequate flow and turnover rates.
of the filter elements and media needs to be properly maintained to assure
vacuuming to prevent the buildup of particles that make the water cloudy.
balance — Are pH, alkalinity or calcium hardness levels too high? These
situations can lead to cloudy water problems.
these considerations addressed and problems persisting, may need to consider
addition of water clarifiers or other preventative specialty chemicals to
maximize water quality.
H2O2: Advantages Rapidly oxidizes H2S and is a more cost effective alternative for facilities considering elimination of chlorine gas. An environmentally friendly oxidizer, that produces no chlorinated byproducts. Adds dissolved oxygen to the waste stream which helps to maintain aerobic conditions and inhibit H2S regeneration.
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