Jeffrey D. Maxey
Consulting &
Training Services
National Aquatic Conference
Atlanta, Georgia 2007
The development of diatomic elemental gas chlorine applications in the disinfection of water was claimed by
LIFE Magazine in 1997 as one of the “greatest advancements in the history of public health” and listed it as
the 46th most significant event of the millennium. In 1998, it was hailed by the Center of Disease Prevention
and the World Health Organization as “One of the centuries greatest health achievements.” Chlorine, from
the Greek work meaning greenish-yellow, was discovered in 1774 by the Swedish chemist Karl Wilhelm.
Since that time, the halogen can be attributed with innumerous contributions to everything from photography
to dry-cell batteries, from polyvinyl chloride (PVC) to textiles, from pharmaceutical germicides to perhaps the
greatest household and commercial disinfectant known to man. Yet when you ask an untrained layperson
about chlorine and its contributions to the swimming pool industry, they immediately turn up their nose, and
think only of red eyes, itchy skin and a disagreeable odor that often times remains with them long after they
have left the swimming pool. Throw in some disinfection byproducts in chlorobromo hydrogen carbons such
as trihalomethane chloroform (thought to be carcinogenic), renal and liver complications, eczema, asthma,
frontal sinus inflammation, and enormous storage and handling concerns, and it will leave even the most
devoted proponent wondering why we are still having this stuff delivered by the truckload.
The answer is simple……chlorine does two thing extremely well: Oxidation and Sanitation. Oxidation, the
process of chemically “burning” organic debris from the pool water, and sanitation, the process of
deactivating the pathogenic organisms in the pool water, can both be achieved with relative predictability with
a reasonable residual of free, active, unadulterated chlorine. This ability to perform both of these functions
while holding a residual is what has made chlorine the one-stop shopping treatment remedy for many years.
Chlorine was first introduced in the treatment of swimming pool water in the late 1920’s and the powerful
disinfection and oxidation properties inherent in its insertion made enormous advances in the treatment
process that would later be coupled with recirculation efforts in the 1940’s. However, the undesirable
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byproducts, unsubstantiated health concerns, and the misunderstanding of the complexities associated with
treating swimming pool water led researchers to begin immediately looking for an alternative.
Today, more times than not we are still chlorinating swimming pools. Amidst the auspices of “Science and
Technology” there are several “challenges” to traditional chlorinated swimming pool treatments, some of
which have financially entrenched themselves in the residential swimming pool market for many years to
come. Seldom do we see any marketing campaign launched surrounding some new fan fangled treatment
mechanism or chemical protocol that is not invariably accompanied by the claim that it will significantly
reduce or eliminate entirely the need for chlorine.
But the commercial swimming pool is a different beast all together. Today our swimming facilities are
subjected to enormous organic introductions that not only require, but demand our ongoing diligence and
attention. Today, it is not enough for our aquatic professionals to only have a remedial understanding of
acceptable and ideal chemical tolerances. Today, we must come to understand the relationship of the
multitude of attributes in operating a swimming pool “system”. That is to say, that we must not only
understand that a chemical is present or a system is running properly, but we must also fully understand
what it is charged with doing, how it relates and influences the other components of our overall chemistry,
and how it compares with other alternatives, both from a performance and financial standpoint.
To know what enters, and eventually exits the commercial marketplace and to have an understanding of the
advantages and disadvantages of these “snake oils” may prove invaluable in protecting the fiscal integrity of
those charged with the safe operation of a commercial aquatic facility.
Authors Note: This section is provided for
informational purposes and those of you who
are adept at chemistry will fully understand the
simple equations of how chemicals react in
solution. While the overall outcome that the
chemical provides and the understanding that
the chemicals are inextricably linked in function
and performance is essential in understanding
swimming pool chemistry, to have a complete
understanding the chemical behaviors, given a
significant number of variables remains virtually
unimportant in ensuring the success of the operator. These equations, by their definition, are academic and
offer little practical assurance of being proficient with their application in the field. In other words, if these
equations merely confuse you, do not allow that to diminish the experience associated with understanding
the fundamental practical applications of their administration in real terms.
Chlorine is one of the most abundant and useful chemicals on Earth and is produced industrially from the
compound sodium chloride, otherwise known as ordinary table salt. Its diatomic or elemental gaseous form
can be derived by applying electricity:
2 NaCl + 2H2O
Sodium Chloride
(Salt)
Water
Cl
Electricity
2
Chlorine Gas
+
2NaOH
Sodium Hydroxide
(Caustic Soda-Lye)
+
H
2
Hydrogen Gas
This is the elemental formation and is largely done the same way in modern day chlorine (salt) generation
systems. Whether chlorine is introduced as chlorine gas (elemental) or in one of many compounds, an utterly
predictable result occurs:
2
XCl
+
Chlorine
Product
HO
HOCL
2
Water
+
Hypochlorous Acid
XBP
Chlorine Byproduct
pH
Dependant
OCl-
H+
Hypochlorite Ion
Hydrogen Ion
Hypochlorous Acid is the active oxidizing a sanitizing agent and it is the strong desire of the operator to
encourage conditions that would lead to the most significant HOCl activity with each pound of chlorine that is
added to the pool. The disassociated (ionized) molecular structure in OCl- and H+ are far less effective from
a performance standpoint. In all cases, regardless of the type or method chlorine delivery, powerful
Hypochlorous Acid is developed, along with a byproduct that largely dictates the pH influence of the
chemical:
Elemental Chlorine
(Gas)
Sodium Hypochlorite
(Liquid Bleach)
Cl2
+
Gas
NaOCl
Sodium
Hypochlorite
H2O
HOCl
Water
+ H2O
Water
Calcium Hypochlorite Ca(OCl)2 + 2H2O
(Granular/Briquette)
Lithium Hypochlorite
(Powder)
Calcium
Hypochlorite
Water
LiOCl + H2O
Lithium
Hypochlorite
+
Hypochlorous
Acid
HOCl
+
+
Hypochlorous
Acid
Hypochlorous
Acid
3
Cl-
Na+
+ (OH)-
Sodium Hydroxide
pH >13
HOCl +
Water
+
Hydrochloric Acid
pH <1.0
Hypochlorous
Acid
HOCl
H+
Ca+2 + 2(OH)Calcium Hydroxide
pH 11.8
Li+
+ (OH)-
Lithium Hydroxide
pH 10.7
Cyanuric acid (C3N3O3H3), often times called “Stabilizer” or even “Conditioner” for reasons that we cannot
comprehend, was then heavily utilized in outdoor installations to protect the chlorine molecule from complete
destruction due to the destructive UV rays of sunlight. As luck would have it, the capital venture folks pressed
the cyanuric acid into the chlorine compound and the birth of two chlorinated isocyanurics came about:
Trichlor
(Tablets)
Dichlor
(Powder)
C3N3O3Cl3 +
Trichloroisocyanuric
Acid
3H2O
HOCl
Water
Hypochlorous
Acid
NaCl2C3N3O3 + 2H2O
Sodium
Dichloroisocyanurate
+
C3H3N3O3
Cyanuric
Acid pH 3
HOCl + NaOCl + C3H3N3O3
Water
Hypochlorous
Acid
Sodium
Hypochlorite
Cyanuric
Acid
pH 6.8
Admittedly ominous looking, these two chemicals act in their simplicity with utter predictability in that the
desired hypochlorous acid is developed and a byproduct, in this case, cyanuric acid remains. Hence, the
dilemma of elevated levels of cyanuric acid and consequent poor chemical performance is validated. This
debate is outside of the scope of this topic and is therefore not addressed further.
Remember high school or college chemistry? Some less than socially acceptable professor likely asked you
at one time or another to memorize this seemingly ridiculous chart, or at least a series of properties
associated with the first eighteen. Being the studious person you were, you applied every clever mnemonic
device, regurgitated it in class, and promptly forgot it all in hopes of never having to see it again. Not to be
the bearer of bad news, but if you tax your selective memory, you will remember that the periodic chart was
situated this way for a reason. Based on the atomic orbital and the number of electrons in the outer shell, the
elements would be positioned into periods and groups and then into families based on their chemical
properties and behaviors. The Halides are a family of elements that are just one electron shy of a full outer
shell. Why is this important? It is not. What is important is that this makes this family of halogens extremely
reactive and gives rise to perhaps the most widely used challenge to traditional chlorine.
Chlorine
Bromine
Halides
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I. Bromine
As one might expect, Bromine when added to water, reacts similarly to chlorine. It is administered to pool
water in two different ways, though only one commercially. Sodium Bromide is a stand-alone salt that is
added to the pool and needs an oxidizer to activate it, usually chlorine, potassium monopersulfate, or ozone.
BCDMH, or stick bromine is a hydantoin based compound that is actually bound to an organic molecule and
carries its own oxidizer, usually chlorine in an amount of 25-30% of the weight per pound. In either
application, the desired result is Hypobromous Acid. Sound familiar? If not, take a look;
XBr
Bromine
Product
+
HO
2
Water
HOBr
+
Hypobromous Acid
XBP
Bromine Byproduct
pH
Dependant
OBr-
H+
Hypobromite Ion
Hydrogen Ion
One of the characteristics of bromine is that its active component in hypobromous acid is unavailable without
the assistance of a catalyst. BCDMH applications produce both HOBr and HOCl which might well serve as
argumentative fuel against bromine as many of the undesirable byproducts will be realized with the addition
of chlorine. With that being said, let’s examine the advantages and disadvantages.
Advantages:
 Bromine is far more stable in elevated heat conditions. Chlorine begins its temperature
degradations at 37º F. Bromine does not begin temperature degradation until the water reaches
105º F. This is why we see Bromine as a realistic choice for commercially operated whirlpools
and hot tubs, customarily kept at 103-104º F.
 Bromine combines with ammonia (NH3) to form bromamines (Monobromamine NH2Br,
Dibromamone NHBr2, and Nitrogen Tribromide NBr3). However, these combined ammoniated
contaminants are still excellent disinfectants, have a far less disagreeable odor and are less
irritating to the eyes, skin and mucus membranes than their chloramine counterpart.
 Hypobromous acid activity is greater than hypochlorous acid at the pH tolerances of usual
swimming pool water. For instance, at a pH of 7.5 bromine yields 94% hypobromous acid activity
while at the same pH, chlorine will only convert 50% to active hypochlorous acid.
 Bromine is considerably more pH neutral than any form of chlorine (With the exception of dichlor
which is not widely used for a number of reasons). BCDMH carries a pH influence of about 4,
which makes the pH remediation program relatively simple using nominal amounts of soda ash
or sodium bicarbonate to counterbalance the lowering pH influence.
 In BCDMH applications, once HOBr reacts with the organic matter in the water, Bromide ions are
produced (Br-). This “spent” bromine can be reactivated into active hypobromous acid (HOBr) in
the presence of hypochlorous acid (HOCl) already present from the BCDMH product. Therefore
a “Bromide Bank” of sorts in a regenerative system exists.
Disadvantages:
 Bromine is a substantially weaker oxidizer than chlorine, even at elevate residuals. It is however,
an exceptional sanitizer. But remember that disinfection, though arguably the more important of
the two functions of water treatment, is the easier of the two treatment obligations to achieve. In
other words, oxidation is the hard part, and sanitation is the easy part. On heavily used
commercial pools, bromine is simply incapable of “keeping up” with the tremendous organic load
experienced. This may lead to cloudy and dull water conditions that often times necessitate
regular shock treatments using what else? Chlorine!
 Bromine applications are comparatively more expensive than all chlorine treatment options.
 BCDMH contributes to considerable total alkalinity loss, which will necessitate notable and costly
sodium bicarbonate additions.
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

Bromine is equally, if not more readily degraded by sunlight and is incapable of being stabilized
by a chemical such as cyanuric acid. This makes bromine a poor choice for outdoor installations.
Marcite plaster installations become noticeably yellowed using BCDMH applications.
There is presently no test that will determine the amount of sodium bromide present in the pool,
only the amount that is activated. This can cause operators to sometimes “fly blind” in respect to
actual pool conditions as they are metering their appropriate levels in a brominated pool by
adding a chemical that has no bromine component to it.
Bromine is soft on algae and algae blooms have been known to thrive even at elevated levels of
hypobromous acid. To deactivate the algae bloom, the operator is often time forced to add…..
ya’ guessed it, Chlorine!
II. Hydrogen Peroxide and UV Light
Remember when you were a kid and you got that cut or scrape
and immediately mom pulled out that brown bottle of hydrogen
peroxide? She would pour it over the wound and it would
bubble….. that is sanitation.
Then, in the 1980’s when every partially blonde adolescent
wanted that Loni Anderson look and that same brown bottle
did the trick? Well, that is oxidation…..or at least a portion
thereof. Hopefully this sounds familiar to the two processes
that we attempt to perform on our swimming pools and yes, for
some time Hydrogen Peroxide has done a fair enough job to
deserve mention.
Hydrogen peroxide (H2O2), at a 35% concentration by weight has used its natural decomposition makeup of
dissolved oxygen for water treatment for several years. Due to the fact that it is a rather poor disinfectant
(when compared to chlorine, bromine, ozone) it is not approved as a stand-alone treatment for microbial
control in water systems, swimming pools or spas. However, there are a number of technologies that use
peroxide as part of a treatment system in an effort to improve the performance of other disinfection methods.
In cooperation with UV Light, ozonation, silver salts and polyhexamethylene biquanide (PHMB) sanitizers,
peroxide has been investigated and touted as the way to finally rid yourself of that pesky chlorine.
Used in conjunction with UV light, Hydrogen Peroxide has perhaps found its most reliable commercial
application. UV light exposure, or the process by passing water through clear quartz tubes for exposure to
brightly lit UV-spectrum fluorescent bulbs, does a good job with disinfection. Hydrogen peroxide, otherwise a
poor disinfectant but an extremely powerful oxidant, performs the other mandatory function of water
treatment and a synergistic relationship between the two treatment vehicles is apparent. In other words, what
one does not do, the other will.
Seemingly having extraordinarily reliable results, the argument that the two in cooperation would find
enormous favor in the commercial market…. that is, until someone went to pay for it. The significant initial
capital expenditure associated with its installation coupled with the consumable operational cost of the
Hydrogen Peroxide, the ongoing maintenance of the UV equipment, and the unusually high residuals
necessary for proper treatment make the UV peroxide system a perfect alternative for those that have
unlimited financial means.
Advantages:
 Hydrogen Peroxide coupled with another function (UV Light or PHMB sanitizers) for effective
disinfection may well be a viable alternative for those with halogen hypersensitivity and who
have little tolerance for Chlorine, Bromine and their byproducts.
 Despite its power, Hydrogen Peroxide is a natural metabolite of many organisms. Consequently,
there is none of the problems associated with the gaseous release or chemical residues
associated with other chemical oxidants. Since H2O2 is completely miscible with water, the issue
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
of safety is only one of concentration. As Hydrogen peroxide has a molecular weight of 34.02, it
is absolutely nonflammable at any concentration.
Hydrogen Peroxide is a stronger oxidant than many commercial pool applications, including
chlorine. In cooperation with UV Light, a process of catalysis achieves even greater oxidation
potential in the development of highly reactive Hydroxyl Radicals (-OH), second only to fluorine
in reactivity.
Oxidant
Fluorine
Hydroxyl Radical
Ozone
Hydrogen Peroxide
Potassium
Permanganate
Chlorine Dioxide
Chlorine
Potential, V
3.0
2.8
2.1
1.8
1.7
1.5
1.4
Bromine


Through oxidation, hydrogen peroxide can reduce the amount of organic nutrients present in the
water assisting with control of bacterial development and proliferation.
Assists in water clarity by eradicating suspended and dissolved organic matter.
Disadvantages:
 High concentrations, usually 30-40 ppm of hydrogen peroxide is necessary for swimming pools
with limited organic load, and up to 100-150 ppm for heavily used pools.
 Hydrogen Peroxide is very expensive and stores poorly.
 UV Light is an “outboard” treatment mechanism, meaning that its exposure happens behind the
scenes in the pump room. Only that water that see exposure is treated, so a relatively poor
disinfectant in hydrogen peroxide is charged with the “residual” based treatment in the swimming
vessel itself.
 Hydrogen peroxide cannot be used with Diatomaceous Earth Filtration systems because it
reacts with the D.E. and causes it to dissolve.
 Hydrogen Peroxide also removes chlorine from the water. So pools using chlorine as a
supplemental treatment may not consider peroxide based systems.
 Hydrogen Peroxide decomposes much more readily at elevated temperatures (2.2 factor
increase for every 10 degree rise Cº).
 Hydrogen Peroxide decomposes readily at any pH that is greater than 6.8, which hopefully, is
where our pools are kept. Hydroxyl Radical formation is virtually non-existent at customary pool
pH levels and may not be realized until pH levels reach 8.2 or greater.
 Hydrogen peroxide is degraded, though to a lesser extent by sunlight.
 UV systems only work well when water clarity is good. Turbid water conditions can hinder, if not
completely interrupt the disinfection process.
III. Ozone
Well, the search is over. You can all go
home. Researchers in their infinite
search for a more powerful oxidizer and
sanitizer than chlorine, looked to this
largely European technology….being
able to generate, harness, and use (as quickly as possible) trivalent oxygen, otherwise known as Ozone
(O3)……. and yes, without argument or exception, believed that they had found it. But if you remember back
to the third reason that chlorine has long substantiated its place in commercial pool applications, its ability to
7
hold a residual, Ozone, despite its power and prowess, still misses the mark in the versatility enjoyed by
halogen treatment options.
Ozone, by its simplest definition is merely another form of oxygen. However, in its trivalent composition, it is
extremely unstable, serves as an excellent disinfectant, and a very powerful oxidizer. Locally generated by
two different methods, ozone gas does an extraordinary job of destroying pathogens, in some cases,
immeasurably faster than chlorine. But in the immortal words of Kent Williams, author of the AFO program,
“A dead bug is a dead bug……….whether it happens in one one-hundredth of a second or one-quarter of a
second, it is still a pretty dead bug”. With that being said, it is worthy to recognize that in the cryptosporidium
era, ozone does show that it is a far more effective on deactivating protozoan cysts, amoebas, viruses, and
spores, all of which, depending on their makeup can be problematic from a hygienic point of view.
Ozone is generated both from UV light and what is known as corona-discharge methods. As the former does
not produce enough ozone for it to satisfy the “primary oxidation” requirement of commercially used pools, it
deserves no further mention for our purposes here. The later, corona-discharge method can produce high
concentrations of ozone which when coupled with sufficient reaction based contact time, can substantially
reduce, if not eliminate the need for chlorine all together. What? Did he say eliminate? Please do stay
tuned…………
The CD method of generating ozone is performed by passing air that is dried to a -60 dew point or greater,
through a dielectric assembly where high voltage electrodes split the oxygen (O2) molecules and provide
them an environment to recombine as O3, otherwise known as ozone.
The ozone is then inserted through a side stream venturi, where it rejoins the full water circulation and is
placed in a contact chamber, or reaction vessel. Providing the units are sized to make enough ozone, and
the contact time is sufficient (CT value of 1.6 ppm or greater ~ 0.4 ppm for a period of 4 minutes, or greater
concentration with less contact time), the ozone has the opportunity to fully perform the “primary oxidation”
function of water treatment. To finish the ozone’s travel through the system, it is then off gassed and stripped
from solution using granular activated charcoal (GAC) or anthracite.
Carbon Destruct
C +
Carbon
2O3
Ozone
CO2 +
Carbon Dioxide
2O2
Oxygen
Food for the Green Stuff
8
With arguably the more difficult part of the water treatment (oxidation) being handled in the pump room, a
significantly smaller amount of another residual based disinfectant can be added to the pool to satisfy the
pool’s sanitation needs. What might that be? Yep, ya’ guessed it……..chlorine or bromine. Welcome back to
the halogen based by-product discussion that brought us here in the first place.
Author’s note: Ozone Bromine systems have been investigated and placed into use on many installations in
the United States. Originally, the technology associated with the Bromide Ion regeneration using Ozone
appeared promising but failed in many installations due to the undersizing the of Ozone systems from the
outset. Remember that Bromine is not a comparatively good oxidant. So for Ozone Bromine systems to work
well, even amidst the promise of bromide ion regeneration, ozone simply must be capable of performing the
primary oxidation function that we are speaking of. Due to time constraints, Ozone/Bromine systems are not
going to be discussed specifically in this session.
Unfortunately, as American and Canadian treatment standards bastardize the German Din-Standard
application in the interest of saving space and money, the European perfection of the process remains in
tact. Being that properly sized and installed CD systems servicing several bodies of water can cost literally
hundreds of thousands of dollars, we find the ozone system in most installations to be the first of several
project saving “value engineering” efforts while undertaking the task of building new facilities.
Advantages:
 Properly sized ozone systems that perform primary oxidation allow operators to carry (within
state standards) up to one-tenth the amount of chlorine (or other disinfectant). The reduction in
halogen consumption is self-evident. However, when coupled with GAC filtration chlorine is lost
to that process so savings are not as dramatic as original claims. Less chlorine or bromine
means fewer odors, less irritation, etc…
 Less disinfectant results in commensurate reductions in the chemicals used to adjust pH.
 Ozone, in the presence of chlorine, helps prevent the formation of chloramine compounds and
can eradicate urea, amino acids, and other ammonia based contaminates.
 Ozone helps to remove organic material before chlorine has an opportunity to react with it,
diminishing the formation of trihalomethanes (THM’s) and polychlorinated biphenyls (PCB’s).
 Ozone oxidizes absolutely everything including perspiration, urine, creatine, creams,
ointments, cosmetics, and nasal secretions.
 Eliminates the hazards associated with transportation and storage of large amounts of
chemicals.
 Ozone converts oily and gelatinous organics to carbon dioxide (CO 2), which eliminates the need
for costly enzymes.
 Ozone does not have a disagreeable odor.
 Ozone does not bleach hair, does not dry skin and does not stain the pool surface (it even
serves to remove dissolved metals that may discolor the surface).
 Ozone acts as a flocculent and coagulates particulate matter to allow the filter to perform more
effectively. This leads to slower Total Dissolved Solid (TDS) build up.
 Ozone makes you swim faster! Now, allow me to clarify………if it takes you, like me, a veritable
eternity to traverse your rounded frame across the pool, I do not think that swimming in an
ozonated swimming pool will make a lick of difference. However, to the elite swimmers of the
world, the dissolved oxygen and more complete oxidation process is argued to have an impact
on the friction experienced and therefore makes for a “fast pool”…or so they say.
Disadvantages:
 Initial purchase expense for CD systems is enormous. Take a normal pump room, double the
cost and you too, can have a properly sized ozone system.
 As much of the technology is grounded in European markets, parts for specific systems can be
very expensive and difficult to acquire.
 Large systems are temperamental with innumerous components that must work in cooperation
with each other for the unit to work properly. A single problem with something as simple as a
solenoid valve, booster pump, or a voltage transformer, can make the entire system inoperable
while awaiting specific parts for repair. This cycle can be so problematic that I have heard
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

personnel charged with their maintenance say, “Ozone works great when it is operating
properly…..too bad we have only witnessed that as often as Haley’s Comet!”
Ozone oxidizes absolutely everything including booster pump impellers, copper heat
exchangers, mechanical seals, rubber “O” ring gaskets, improperly prepared contact chambers,
injectors, delivery tubing, the inside of the ozone cabinet, etc…You get the idea.
Ozone leak and air quality monitoring equipment must be installed. This equipment is very
expensive and must be calibrated annually at notable expense.
Ozone is not only a bad algaecide, but actually encourages algae growth by supplying the active
bloom with all the nutrients it needs to live and prosper.
IV. Ionization
Try this! Google the words “Chlorine Free Swimming” and watch the ion generator companies pop up like the
Whack-a-Mole game at your local arcade, all with outlandish claims that they hold the truth, the light, and
certainly the way. My textbook rule of thumb is anytime a sales person says the words, “This unit will pay for
itself, over and over again”, turn and run……in the opposite direction…….fast! I have found amusing, the
unusual and creative products that have arisen under the label of “ionization” over the years. Everything from
“capsules” that you drop into your skimmers to actual “floating” treatment discs that are powered by the sun,
all with cute little names, and all of which are using ionization of metals to get you off of chlorine –
permanently! Their marketing efforts and the zeal by which they promote this saving grace technology is all
accompanied by the obligatory section entitled “Health Hazards Associated with Toxic Chlorine Use”, which
after reading would leave even the least judgmental of us thinking that chlorine will surely be responsible for
the Armageddon, when and if it comes. Then, they loft into windy testimonials about dried out skin, red eyes,
bleached swim suits and how they literally “plucked” their family away from swimming in “toxic” (toxic always
precedes the word chlorine) chlorinated pool water. I mean really, why would anyone swim in poison? By the
time the picture is painted, we envision our swimming pool waters glowing neon green with thick sludge and
pungent emerging gases. Consequently, anything looks like a viable alternative at that point. But do they live
up to claims that they will completely eliminate the need for chlorine? Regrettably, in public pools, the answer
is no. Here is why.
Read further in the product description and it will talk about sanitation…….sanitation of this, disinfection of
that. Nowhere, will you ever see the word “oxidation”. Wanna’ know why? Because there is none, nil, zip
ziltch, not one little iota!
Since its introduction, silver and copper ionization systems have ingrained themselves in the residential
market for years to come. And why wouldn’t they? No one really uses those pools. They sit empty the
majority of the time and a heavy organic load would otherwise be measured with a visit from the neighbor’s
children on a Saturday afternoon. But the ionization systems that leaped into and attempted to demonstrate
their promise in the commercial marketplace were largely proven unsuccessful and consequently, left the
scene about as quickly as they arrived.
Now, the story is not all bad. Ionizers do sanitize. Positively charged Silver (Ag+) and Copper (Cu+ and
Cu2+) ions are charged through a process of electrolysis. Electrodes are placed close together inside the
flow of water through the recirculation system. As electrical current is applied or generated by the flow itself,
the outer atoms lose an electron and become positively charged. As the charged particles attempt to bridge
the gap, one to another, they are literally swept away by the flow of the water and impart poisonous
conditions to the various microorganisms that have found their way into our pool water. Electrically charged
copper ions (Cu2+) in the water search for particles of opposite polarity, such as bacteria, viruses and fungi.
Positively charged copper ions form electrostatic compounds with negatively charged cell walls of
microorganisms. These compounds disturb cell wall permeability and cause nutrient uptake to fail. Copper
ions penetrate the cell wall and as a result, they will create an entrance for silver ions (Ag +). These penetrate
the core of the microorganism. Silver ions bond to various parts of the cell, such as the DNA and RNA,
cellular proteins and respiratory enzymes, causing all life support systems in the cell to be immobilized. As a
result, there is no more cellular growth or cell division, causing bacteria to no longer multiply and eventually
die out. The ions remain active until they are absorbed by a microorganism or precipitate from solution.
10
Whoa…. that is an awful lot of science just to say that the thing kills bugs! Remember not so long ago that
we had explained that there are two vital functions of swimming pool water treatment ~ Oxidation and
Sanitation. That oxidation is the hard part and is the reason we carry substantially higher levels of chlorine in
the swimming pool. The process of sanitation, the easy part, is likely being achieved by the first tenth of a
part per million of free active chlorine in the water. So, it begs the question, if we need to add 1.0 -1.5 ppm of
chlorine in the interest of oxidation, and sanitation is being fully satisfied in the first .1 ppm, and ionizers are
only sanitizing the pool water, what is it that this machine is doing?
The front of the older fashioned cabinets had a set of lights that would flash on and off, back and forth and
around in a seemingly random and excitable fashion. The feeling of energy derived from these flashing lights
would lead even the most scientific of us to say, “I have no idea what this thing is doing, but it looks like
whatever it is, it must be pretty cool!” Well, it is doing something.
Advantages:
 In residential, or extremely light duty public pools, ionization may reduce halogen consumption.
With a supplemental sanitizing agent, chlorine would debatably be “freed up” to tackle the more
burdensome oxidation needs.
 Copper-silver ionization affectively deactivates Legionella bacteria and bio film.
 Copper-silver ionization has a larger residual effect than most other disinfectants. Copper and
silver ions remain in the water for an extraordinarily long period of time and are considered
“active” until absorbed by a microorganism
 Copper-silver use does not depend on water temperature, which makes it a reasonable
alternative in low load spas and whirlpools.
 Copper-silver is non-corrosive which means it causes less strain on the distribution system.
 Copper ions serve as a relatively good algaecide.
 When copper-silver ionization is applied, there are no transport and storage difficulties.
Disadvantages:
 High TDS levels, which are exacerbated by ionization itself, are extremely detrimental to the
ionized metal treatment process. In high conductivity water, ionized metals fail to work properly,
or may fail completely, and silver ions will precipitate black and stain.
 Copper staining can occur due to the excess ions “plating” out or precipitating, particularly at
elevated pH levels.
 Silver ions easily react with chlorines and nitrates that are present in the water, causing them to
no longer be effective. Chlorine and ion generators are fundamentally incompatible treatment
options in the same system.
 Some species of microorganisms can become resistant to silver ions. They can remove metal
from their systems or convert it to a less toxic product. These microorganisms can become
resistant to copper-silver ionization all together.
 When the water has high concentrations of calcium, fouling takes place and there will be a
decrease in electrode release.
 For commercials pools with even a moderate organic load, the process of oxidation will need to
be satisfied and ionizers do not accomplish this vital function of pool water treatment.
V. Chlorine Generation
The thing about science is that with all variables remaining the same, we
can expect utter predictability in the outcomes of a chemical being added to
water. And so is the case with Chlorine Generation, otherwise improperly
referred to Salt Generation Systems. The irony of chlorine generation
making it to our slated topics of discussion is that the treatment process is
not a challenge to chlorination at all. It is merely a modification in the
method by which we derive the chlorine that is to be introduced to the
swimming pool. Once the chlorine is in the water, the laws of science, as
one might expect, take over. Chlorine is chlorine regardless of whether we
make it on site, or have it delivered on pallets.
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Using common salt, Sodium Chloride (NaCl), chlorine generation has been around for many years as an
alternative to the costly chlorine purchase and insertion. Using electrical current in the form of concentric
cathode and anodes assemblies immersed in a salt solution, elemental chlorine may be “released” from the
salt compound and delivered in its free, radical fashion to form reactive and effective Hypochlorous Acid
(HOCl) to both oxidize and sanitize pool water. As with all chlorine insertion methods, a by-product is
produced. Let us start, yet again with how chlorine gas is derived and break down the reactions and their
respective byproducts and pH influence:
Vent
2NaCl + 3H20
Salt
Water
Cl2 +
Chlorine
Gas
Electricity
Cl2
+ 2NaOH +
H2
Chlorine
Gas
Sodium
Hydroxide
Hydrogen
Gas
H2O
HOCl
Water
Hypochlorous
Acid
+
HCl
Hydrochloric
Acid
pH Scale
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Follow the chemistry. You do not need to be a nerd like me to think that the process is pretty cool! By taking
ordinary table salt (NaCl) and applying electricity, we obtain elemental gas chlorine (Cl2). This gas chlorine
actually bubbles up to form sodium hypochlorite Na(OCL) 2. Insertion of gas chlorine into water will produce
the desired hypochlorous acid (HOCl) and a byproduct of hydrochloric acid (HCl), which leads to a drastic
downward shift on the pH scale. Meanwhile, sodium hypochlorite releases the byproduct sodium hydroxide
(NaOH), otherwise known as caustic soda. Anyone who has ever worked with caustic soda would agree that
if there were a 15 on the pH scale, this stuff would proudly be sitting there! Vent the hydrogen gas (H 2),
throw it all back into the pool and you have a surprisingly pH neutral chlorination treatment (although
emerging pH will still need to be addressed). And the truly cool part has not yet happened…the used and
excess chlorine reverts back to form sodium chloride (NaCl) to be used over and over again.
1. In-line Generation
A fairly low concentration of salt is added to the pool (3000-4000 ppm). Electrolysis occurs in an
electrolytic cell that is placed directly in the mainstream of the recirculation water.
NaCl
Pool
Filtered Water
Electrolytic Cells
Chlorinated Water
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In-line Electrolytic Cell
Anode (+)
Cathode (-)
NaCl
Flow
HOCl, NaOH, HCl, H2
By passing water through these in-line cells, Hypochlorous Acid is produced along with
conflicting by-products in the form of Hydrochloric Acid and Sodium Hydroxide. As the impact of
NaOH is greater than that of the HCl, the chemical is delivered at a pH infuence of roughly 9.0.
This will still lead to emerging pH levels over time that will need to be addressed by the operator.
2. Diaphram/Brine Method Generation
Two chambersare seperated by an osmotic membrane that permits the passage of sodium ions
and electrical current, but prohibits the transfer of chloride ions. The anode containing a positive
current and dissolved salt in distilled water is in one chamber, while the cathode, or negative
current and distilled water is in the other. Electricity is applied and chlorine is produced similarly
to the in-line method. However, chlorine gas is collected at the top of the brine solution cahmber,
is drawn off using venturi and inserted under vacuum to the pool. The second chamber receives
the sodium ions and with the cathode, sodium hydroxide (caustic soda) and hydrogen gas are
produced.
Pool
Cathode
--
Pool
Anode
+
This system allows for the generation of chlorine without “salt seeding” the pool water itself. The
chlorine gas is inserted, the hydrogen is off gassed to atmosphere and the sodium hydroxide (ph
13
14) and Hydrochloric Acid (pH 1.0) are conversely introduced to the pool in a theoretically pH
neutral application. Yet again, the pH effect over time is increasing which will have to be
addressed by the operator.
3. Sodium Hypochlorite Generation
The last method is called Sodium Hypochlorite Generation, in which an .08% ACC solution of
sodium hypochlorite (liquid bleach) is generated, stored, and delivered on site. Using a salt
dissolver, a 30-35% salt solution is substantially diluted and is passed through an electrolytic
cell. A low DC current is applied and sodium hypochlorite is produced.
NaCl +
Sodium
Chloride
H2O + 2e
Water
NaOCl
Energy
+
Sodium
Hypochlorite
H2
Hydrogen
Gas
Hydrogen
Vent
Electrolytic
Sodium
Hypochlorite
Bulk
Storage
Cells
Pool
Salt
Dissolver
This simple diagram illustrates how a .07-.09% Available Chlorine Content solution of sodium
hypochlorite can be generated on site, stored and introduced as needed. The generation of chlorine
begins and ends based on the amount of chemical desired, and level control mechanism located in
the storage tank. This approximate .08% solution is delivered at a pH of roughly 9.0 versus the 13.0
experienced with bulk delivered chemical.
It is important to note that the problems that have been experienced in the commercial market have
not necessarily been with the technology of chlorine generation itself, but more so with the under
sizing of the units themselves. The amount of chlorine consumed is always 100% commensurate
with the organic load on the pool. Lots of people means lots of chlorine. Few people means very little
chlorine consumption. The problem with commercially sizing salt generation equipment has been the
inability to prepare for the most extensive call for chlorine at the busiest time of the day.
Let’s say that you take the leap and decide that chlorine generation is the “Choice of Champions”.
You have the equipment written up in a specification and are asked the question, “How much
chlorine do you use in a day?” Seems like a reasonable question, so you answer 10 lbs. The
company then dials up a price on a 10lb/day unit and within the first week you are frustrated to find
that the unit is not even close to keeping up with demand. What you failed to realize, is that you
might be using 90% of that 10 lbs in a three hour period of the day….that being the time that the pool
is most crowded. The company then installs a “back up” chlorinator…. usually a real cheap trichlor
erosion feeder that will supplement chlorine feed for those “heavy use” times. If you were going to
use purchased chlorine, you could have done that from the outset….and trichlor likely would not
have been your choice for that indoor pool!
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There are advantages and disadvantages to each application that are specific to that particular
system. For our purposes here, we will only concentrate on the overall advantages and
disadvantages of chlorine generation as a whole:
Advantages:
 On site generation of chlorine eliminates the need for costly transportation, delivery, and storage
of large quantities of chemicals on site.
 Cost savings experienced are notable when compared to the purchase and delivery of
chlorinated compounds. Usually a 40-50% reduction in consumable operating costs can be
realized.
 After the oxidation and sanitation process is completed, it reverts back to salt so that it may be
used over and over again with limited new salt additions.
 Necessary pH remediation is far less frequent and far more manageable than chlorinated
compounds. All systems reduce the pH impact of byproduct formation.
 In line systems are free from storage ramifications and can produce substantial amounts of
chlorine given the salt content of the water and the energy applied.
 In line method offers virtually no safety and handling considerations. Diaphragm and Banking
systems arguably have the same handling concerns associated with the insertion of purchased
chemicals.
 Water passing through the cell is essentially superchlorinated and some inorganic chloramine is
destroyed. However, ventilation requirements for the process to be complete are not realized.
Disadvantages:
 Obviously, with in line systems, if you add salt to the pool, the pool is going to taste salty. You
might want to prepare your customers before you unilaterally make the change.
 Electrolytic cells are prone to fouling due to calcium deposition on the electrode plates. Reverse
polarity operation is absolutely imperative for proper functioning of the equipment.
 Initial installation cost is far greater than simple liquid chlorine, and erosion or soaker feed
mechanisms.
 Total Dissolved Solid (TDS) levels are increased, by design with the introduction of salt into the
system. Even in outboard systems, salt heavy hypochlorite will lead to increasing TDS levels
calling for more frequent dilution efforts.
 Systems must be substantially oversized to keep up with heavy organic loads or UV depletion on
outdoor installations.
 Outboard systems are capable of producing, at the very most, 2 lbs/day. So multiple units are
required for a busy public pool.
 Outboard systems require space to generate, store and apply the chemical.
 pH will still need to be addressed, although less frequently than with alternative systems.
 Automation of chlorine generation equipment is virtually impossible to achieve.
VI. Medium Pressure UV
I hate to be unoriginal, but I guess it is fitting that we leave the best
for last. Seldom, over the years, have the various marketing claims
associated with the introduction of new technology been realized.
That is until Medium Pressure UV became a widely investigated
treatment option for commercial pools. Ultra Violet light is part of
the electromagnetic spectrum, which includes visible light.
Sunlight, which contains concentrated ultraviolet light, is a strong
natural disinfectant and applications have been in place for many
years for the disinfection of water. As with other treatment options,
there is no oxidation taking place.
Wait a minute…..I know what you are going to say. A minute ago, I
told you that most ionization systems were not worthy of your time
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due to the fact that they only sanitize the pool water. Now I am telling you that Medium Pressure UV is the
“Cat’s Meow”, and it only sanitizes. Ah ha, a contradiction!
Not really……. Only until recently, have Medium Pressure lamps allowed for a broad spectral germicidal
omission that has enabled a diverse set of applications be possible. Medium Pressure UV separates itself
from other “sanitation only” based treatment mechanisms in that the peripheral benefits, other than sanitation
are so attractive that it is certainly worthy of your consideration, and your modernization dollar.
Applied at a broad spectrum of 200-350nm, Medium Pressure UV radiation destroys the ability of pathogens
to metabolize, therefore eliminating their ability to reproduce and damages the intercellular molecules. This
permanently inactivates the DNA cells repair mechanism and deactivates cell proliferation. Even though the
primary action of UV is to kill bacteria, moulds, viruses, and spores, UV treatment, under medium pressure
conditions, also has a secondary function that is of paramount importance to us as pool operators. It
initiates photochemical reactions that destroys chloramines…..the very byproducts that have inspired
researchers (for as many years as we have been chlorinating swimming pools) to continue the search for a
suitable alternative.
Monochloramine (NH2Cl), Dichloramine (NHCl2), and Nitrogen Trichloride (NCl3) are the products of nitrogen
introduction from bather waste forming ammonia (NH3) and reacting with chlorine. These are the complex
contaminants responsible for eye burn, disagreeable odor, poor oxidation, and a host of other problems in
the swimming pool water. What the broad-spectrum output of Medium Pressure has done is allow for the
disinfection of the pool water, and to a large extent much better in this regard than chlorine, while managing
chloramine. Let’s take a closer look.
Visible
Cosmic Rays
Gamma Rays
X- Rays
Ultraviolet
Rays
Infra Red
Radio Waves
Germicidal
Wavelengths
100nm
200nm
300nm
245nm
NH2Cl
(mono)
260nm
NCl3
(tri)
297nm
NHCl2
(di)
400nm
340nm
NCl3
(tri)
By offering this broad spectrum multiple wavelength energy band between 200-350nm, all forms of
chloramines are eradicated. Units today are sized to operate at the highest wavelength of about 315nm as
trichloramine is destructed at two separate wavelengths. But does it work? As much as it pains me to say
that the people who market these things have not engaged in any misrepresentation of the actual capabilities
of this technology, I would have to say, without reservation…..yes!
Remember however, that this is an “outboard” system. This is to say that the actual treatment is an
exposure-based process. The only water that is treated is the water that is actually passing under the lamp.
There is no residual, and there should be no expectation that chloramine will not be formed on a heavy use
day. As a matter of fact, the swimming pool upon gargantuan organic loads can, and does find itself with
16
enough chloramine formation to make a noticeable discomfort for the swimmers in the waning hours of a
heavy use operational day. Not to worry though….this is where the recovery period and turnover rates
become important. It is not uncommon for a pool operator to leave a smelly pool after a long days use, only
to return to pristine, chloramines-free conditions the next morning. It just needed a little time, with no
additional organic introduction, for nearly all the water to see the lamps….say two or three passes.
The good news does not stop there. The disinfection capabilities of these units also make for substantially
more effective deactivation of chlorine resistant bugs. Cryptosporidium and Giardia are virtually
instantaneously inactivated with exposure to UV light under medium pressure conditions.
If you want piece of mind, here it is…for about $35,000 and change depending on the size and manufacturer
of the unit:
Advantages:
 Medium Pressure UV is more affordable than other (CD generated ozone) methods that tout
chloramine management and cryptosporidium control.
 Medium Pressure UV, and the broad-spectrum application initiate photochemical reactions that
eradicate and control all three ammoniated contaminants that are problematic to pool operators.
 Medium Pressure UV is effective in treating for chlorine resistant microorganisms such as
cryptosporidium and giardia.
 Medium Pressure UV, unlike earlier low-pressure installations, actually treat full recirculating flow
for greater exposure.
 New designs with greater hydraulic efficiencies have led to a substantially lower pressure drop
across the system.
 There is NO handling, storage or safety concerns with its application.
 There is reduced halogen consumption. However, depending on the wavelength cycles,
destruction of chlorine from the UV light may offset any savings that would otherwise be
experienced.
Disadvantages;
 This does not eliminate the need for chlorine, bromine, or another chemical charged with the
oxidation of the pool water. Nor does it even allow you to lower the residual.
 The bulbs are expensive and once the intensity of the bulb reaches 60mj/cm 3, the photooxidation and photochemical processes are interrupted. Bulbs can range from $1000-$1500/per,
and the unit may have one or two depending on the model. You can expect about 8,000 - 10,000
hours of service out of each bulb……roughly about a year.
 Units must come with an automatic wiper that keeps the quartz sleeves free from deposits;
otherwise the system is prone to fouling.
I have often been heard saying that if I could only identify a chemical that oxidizes, sanitizes, holds a
residual, initiates no byproduct formation, and does so all while having a pH influence of 7.4……man, I would
die a rich and happy man. Truth is, by its scientific necessity, for a chemical or process to be a good oxidizer
and sanitizer, it simply must be reactive. Unfortunately, we must take the good with the bad in that regard.
Chlorine has a long tradition of doing the very things that we prescribe as being absolutely essential to safe
and healthy swimming. The World Health Organization (WHO) amidst the blitz of self-appointed “tried & true”
technologies, recently stated, “Disinfection by chlorine is still the best guarantee of microbiologically safe
water. This is unlikely to change in the near future”.
So where does that leave us? Well, it probably leaves us trying to find the very best price on chlorine that we
can find. It finds us treating new technologies with a fair amount of responsible skepticism until proven in the
17
commercial marketplace. It finds us looking at ways to not “get off” chlorine, but maybe more importantly,
investigating ways to diminish the negative impact of its use. It finds us enjoying a fair amount of comfort in
the fact that at least today, given all of the challenges, marketing claims, and residentially targeted rhetoric,
chlorinating a swimming pool still provides a reasonable standard of care to ensure the health and safety of
our guests.
Please bear in mind, as you go about your deliberations on “what to try and what not to try”, that the
swimming pool market is a multibillion-dollar business each year. It did not get that way from commercially
operated public swimming facilities. The residential calling for products and services so engulfs the
commercial needs that we appear to be merely an afterthought to the chemical companies and equipment
manufacturers. Recognize that when a new product hits the scene, it is usually:



Residentially sized and is incapable of treating high organic load pools
Has enormously inflated product claims ~ “If its too good to be true, it probably isn’t!”
Has proportionally exaggerated cost savings claims ~ “It will pay for itself over and over again!”
A good rule of thumb is to wait for a year or two before taking the leap. If it is worthy of your consideration, it
will still be around…..some of the kinks will be worked out of it by then, and it will be a lot cheaper as well.
The American Philosopher and Humanist, George Santayana in the early 1920’s was attributed with the
words, “Those who do not learn from the past, are doomed to repeat it”. We have all heard those words and
can see its simple applied wisdom in how we go about the inexact science of managing swimming pools and
life in general. That very same philosopher was quoted later in his career as saying, “Science is nothing but
developed perception, interpreted intent, common sense rounded out and minutely articulated.” Ol’ George
must have been an AFO/CPO, or at least had a pool in his backyard! Truth is, all the scientific understanding
in the world does not make for successful aquatic professionals. It is our sensible use of it that counts.
jdm
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