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Oxidation Reduction Potential (ORP)


“Oxidation–reduction potential (Eh) is a measure of the ability of chemical/biochemical systems to oxidize (lose electrons) or reduce (gain electrons). A positive value indicates an oxidized state, whereas a negative value indicates a reduced state.”

To provide examples, a slight oxidised state would be aerated water, a high oxidised state would be chlorinated pool water and a reduced state would be an environment where anaerobic microbes are active, such as a natural lake.

ORP is measured in millivolts (mV) with the value obtained by two electrodes usually contained in a single unit (sensor). The first (indicator electrode) is typically made of an inert metal such as platinum or gold, where the second (reference electrode) is typically made of silver & silver chloride or mercury & mercury chloride.
Electrons from the water interact with both electrodes, creating a voltage between them and a value is displayed on the main controller.

The response of an ORP sensor can degrade over time and as such requires the probe being tested for accuracy using what is called a standard solution. That is a solution preprepared in a laboratory with a known value at a given temperature. This same standard solution can be used to adjust the measured reading to match the value of the standard. This is known as a calibration of the electrodes (sensor).

ORP is used in the commercial swimming pool industry as a measure of the effectiveness of the sanitiser, which in most cases is chlorine, measured as ‘Free chlorine’.

However, there are two forms of Free chlorine (FCL); the strong sanitiser (Hypochlorous Acid, HOCL) and weak sanitiser (Hypochlorite, Ion OCL-), where the percentage of each in solution is determined by the pH of that solution. The lower the pH value the higher the percentage of HOCL. At a pH of 7.5 the two forms are equal at 50% each in solution.

Because HOCL has no molecular charge and also has a relatively low molecular weight it is better than OCL- in penetrating cell walls of pathogens, so as such is a more effective form of sanitiser. Also, as OCL- has a negative molecular charge, as do cell walls of a pathogen, the two are not attracted, therefore OCL- has little to no effect on the pathogen.

HOCL typically enters the cell wall of a pathogen via osmosis, disrupts the DNA and kills the pathogen. Having a relatively neutral (7.4) pH solution is the trick to allowing the HOCL to effectively operate this way as the pathogen takes solution (containing HOCL) into its cell, as per normal, as if it was just water (H2O) alone, and unaware of its own death warrant it signed in the process.

So why am I now blabbering on about forms of FCL when this article is about ORP? Well, FCL is a measure of the level of (both HOCL and OCL-) sanitiser in a given solution, which means you could have an acceptable level of FCL according to Health Regulations, but a high percentage of it could in fact be OCL- and as such a poor defence against pathogens!

Whereas ORP is a measure of how effective that sanitiser is and a more reliable measure to have in addition to FCL. “ORP ≥650 millivolts (mV), a value defined in the literature as adequate to kill viral and bacterial pathogens within seconds.”

A published scientific research study in the USA found that despite 132 pools and 30 spas were abiding by local Health Regulations (code). The findings were: “Compliance with the Minnesota Pool Code did not assure an ORP≥650 mV (p<0.01). Outdoor pools had significantly lower ORP values than indoor pools (p<0.001). ANCOVA and logistic regression models showed that ORP decreased with increasing cyanuric acid, increasing pH, and decreasing free chlorine.”

The NSW Health Department made changes to the Public Health Regulations 2022 in Part 3: Public swimming pools and spa pools, which includes; “Removal of ORP (Oxidation Reduction Potential) as a method of measuring disinfection effectiveness.” This change took effect in September 2022.
Whilst it’s unclear exactly why they have removed this from the new Public Health Regulation 2022, we can only have an educated guess that it is due to the extensive use of inferior quality ORP system in the commercial space that were not designed for that application and as such should not be relied on to ensure the health of the water for the public.


T. Bastain, et al. Do Traditional Measures of Water Quality in Swimming Pools and Spas Correspond with Beneficial Oxidation Reduction Potential? National Library of Medicine. 2009.

Apera Instruments. How to test ORP. 2018.

T.M. Cogan, Microbiology of Cheese; Encyclopedia of Dairy Science (Second edition), 2011.

NSW Health Department. Public Health Regulations 2022-Key changes. September 2022.


Bromines and their Associated Disinfectant By-Products (DBP’s)


Just like Chlorine, Bromine is used as a sanitiser for recreational water, typically when the water temperature is in excess of 35°C, where such high temperatures would usually degrade chlorine quite rapidly, leaving swimmers susceptible to infection(s). For this reason, Bromine is a common choice of sanitiser for spas.

Bromine reacts with water (H20) to form Hypobromous Acid and Hypobromite Ion (commonly known as Free Bromine), but unlike Free Chlorine, both forms of Free Bromine are strong oxidising agents.

Swimmers release both organic waste, which may include sweat, urine, faecal matter, hair, skin and inorganic waste products, such as sunscreen, makeup, deodorants, and creams during the course of their time in the water.

Chlorine reacts with this various waste matter in the water to form Chloramines, similarly, Bromine also reacts in the same manner to form Bromomines. Bromine and Bromide present in water have the ability to form the Brominated Disinfectant By-Products (DBPs) below:
• Bromoform

• dibromoacetic acid;
• tribromoacetic acid;
• bromoacetic acid;
• bromochloroacetic acid;
• bromodichloroacetic acid
• dibromochloroacetic acid;
• dibromoacetonitrile;
• 2-bromo-2-methylpropanal;
• 2,3,5-tribromopyrrole;
• bromoacetone;
• bromoalkanes;
• bromohydrins; and
• brominated trihalomethanes (including bromodichloromethane, chlorodibromomethane,
and tribromomethane (bromoform)).

The three various ways in which swimmers’ uptake DBP’s include ingestion, absorption and inhalation. However, inhalation of DBP’s can occur to persons not swimming but rather in the surrounding areas of the water. This could include lifeguards, office staff, maintenance staff, parents onlooking, etc.
“Several brominated DBPs have been shown in animal studies to be more carcinogenic than their chlorinated analogs” (Richardson, 2003a).

“Symptoms of acute bromine toxicity via the inhalation route include respiratory irritation/distress and central nervous system effects (all dependant on concentration). Bromine is highly irritating to the skin in both liquid and vapour form, with appearance of injury in the form of often delayed blister formation. Ocular irritation following exposure to bromine vapour is reported. Although rare, ingestion of liquid bromine is associated with haemorrhagic nephritis, with oliguria or anuria, developing within 1 to 2 days.

Where comparisons can be made, the findings from human studies are supported by those from animal studies. The acute toxicity of bromide is considered to be very low”(WHO 2018).

There is currently no regulatory levels or required monitoring of DBP’s here in Australia, but perhaps given the research available and its findings, there really should be for protecting the health of the public.

Written by John Morrison Bsc


World Health organisation (WHO). 2018. Bromine as a drinking – water disinfectant.

Richardson S (2003a). Disinfection by-products and other emerging contaminants in drinking water.

RAA Carter Oz Water. 2015. Disinfection By-products: Not just an issue for drinking water, but also potentially for swimming pool waters. An analysis of three indoor pubic swimming pools and one heated indoor spa in Western Australia.


Accommodation – What are the signs of unhealthy water quality?


Now COVID restrictions have eased across Australia, there has been a real push to support the tourism industry. If you find yourself searching late at night for the best holiday destination and frantically locking in a 50% discounted flight deal, chances are you’ve caught the travel bug!


It’s pretty safe to say, that’s a bug most of us are happy to catch. However, chances are that’s not the only thing you can catch on that long-awaited trip away.


Some travellers either knowingly or not, have packed more than just the makeup bag and swimming trunks. Parasites, bacteria, viruses and other pathogens can also hitchhike their way to the swimming pool of your destination.


The Centre for Disease Control and Prevention (CDC), reported 493 recreational waterborne disease outbreaks were reported from 2000-2014- causing at least 27,219 illnesses and eight deaths.


Almost a third of those were traced to hotel swimming pools or hot tubs.


The major cause was by Cryptosporidium, a chlorine-resistant parasite. It can cause diarrhea, vomiting, nausea, and stomach cramps.


Legionella and Pseudomonas were also responsible for reported outbreaks. Legionella is a type of bacteria that causes Legionnaires’ disease. It results in flu-like symptoms and puts people at risk of severe pneumonia.


Pseudomonas is a common bacterium that can causehot tub rash” and “swimmer’s ear.”


So, who is at risk?

The answer is everyone, though there are those who are more susceptible than others. These include the elderly, pregnant women and children, all of which have weaker immune systems and therefore more likely to fall ill with infection.


What are the signs that the pool water quality is unhealthy?

As the water pathogens reported are all microscopic (not able to be seen with the naked eye), you won’t see them in and around the pool.


Most people look at a pool and see clear water and that is their indicator of ‘healthy water’. In fact, all that indicates is the clarity of the water.  It’s what you don’t see is what you should really be concerned about. Is it there? Or is it not there?


Another common mistake is thinking that the pool is safe if you smell ‘Chlorine’! Pure chlorine, that is used to sanitise pools has no smell. The ‘chlorine’ smell occurs when pure chlorine added to the pool combines with foreign matter (waste products), such as oils, body cells, hair cells, urine, fecal matter, sunscreen and much more. The resulting products are called chlorine by products.


One chlorine by product produced is called Trihalomethane gas. A gas so corrosive that it results in steel structures surrounding the pool rusting. So, you can only imagine what damage it does to our respiratory system. This is the ‘chlorine’ smell that is often identified be swimmers, either in the air, on the skin and hair or on the bikini and board shorts when you get home. You don’t have to be swimming to fall victim to illness, just simply present by the surrounds of the pool inhaling the gas.


So how do we really ensure that the water is healthy to swim in?

Well, firstly, if you smell ‘Chlorine’, turn around, head for reception and demand to know what Secondary sanitation equipment is being used to destroy these nasty water pathogens and chlorine byproducts. If the answer is “we only use chlorine”, know that chlorine as a sanitiser alone will not remove chlorine byproducts, they simply build up in concentration and as such cause more of a concern to the health of guests.


The answer you’re looking for is “we have secondary sanitation equipped to our pool/spa”. These are the following options of secondary sanitation system options available:

  • Ultraviolet light (UV)
  • Ozone gas
  • Advanced Oxidation Process (AOP), a combination of 1 & 2 above producing Hydroxyl Radicals, the most effective oxidizer of waste products and chlorine byproducts known in water chemistry.


These secondary sanitation systems also treat the water pathogens, such as Cryptosporidium (chlorine resistant).


Also know that according to CDC, chlorine alone is limited to the following kill times:

 Free Available Chlorine Germ-Killing Timetable
E. coli 0157:H7 (Bacterium) less than 1 minute
Hepatitis A (Virus) approximately 16 minutes
Giardia (Parasite) approximately 45 minutes
Cryptosporidium (Parasite) approximately 15,300 minutes (10.6 days)



  • Times based on 1 ppm free chlorine at pH 7.5 and 77°F (25°C)
  • These disinfection times are only for pools and hot tubs/spas that do not use cyanuric acid. Disinfection times are longer in the presence of cyanuric acid.

CDC, May 4, 2016.


Written by John Morrison BSc




Hospital Hydrotherapy- Pregnancy, pain and anxiety


Hydrotherapy is a very popular form of exercise for the mature population as well as for rehabilitation of patients experiencing a wide range of injuries as well as those who find land-based exercise too intensive for their body or even for women during pregnancy.


The research is endless for the benefits of water-based physiotherapy!


In this current COVID-19 pandemic, we are all experiencing varying levels of anxiety and searching for ways of best managing it. Can Hydrotherapy play a role?


Woman all over the world that are pregnant and expecting a newborn baby are experiencing the affects of isolation and general uncertainty. Research has shown that hydrotherapy can promote relaxation and decrease parturient anxiety and pain in labor. In fact, research showed that not only anxiety decreased but as did vasopressin (V) and oxytocin (O) levels at the 15-minute and 45-minute time period of immersion in the water.


Pregnant women in their third trimester participating in WATSU (Water Shiatsu), which encompasses passive stretches and massage techniques administered in 35oC warm water, also found a reduction in personal stress, fatigue and pain, improving their quality of life and mood.

Hydrotherapy is often used as a safe, nonpharmacological alternative method to assist women during pregnancy and labor.


Why not search for your nearest Hydrotherapy pool on


Written by: John Morrison BSc.



• Rebecca D. Benfield, et al. The Effects of Hydrotherapy on Anxiety, Pain, Neuroendocrine Responses, and Contraction Dynamic During Labor. Sage Journals. Biological Research for Nursing. May 7, 2010.

• Agnes M. Schitter. Integrative Gynecology and Women’s Health. Effects of Passive WATSU (WaterShiatsu) in the Third Trimester of Pregnancy: Results of a Controlled piolet Study. 1 March, 2015.

• Marylin Stringer, et al. Hydrotherapy Use During Labor: An Integrative Review. Worldwide on Evidence-based Nursing presents the archives of Online Journal Knowledge Synthesis for Nursing. Sigma. 23 April, 2004.


COVID-19, in the Air & on the Surface


Critical new research by the National Institutes of Health (NIS) indicates that COVID-19, a strain of the Coronavirus, can survive in the air and on surfaces for extended periods of time.


The research found that the virus can survive for up to 4 hours on copper, up to 24 hours on cardboard, and 2 to 3 days on plastic and stainless steel.


In addition to contact, the transmission of this virus is also plausible through the air as it was identified that the virus can live in the air for 3 hours in an aerosolized form.


Recently, the use of face masks has become not only recommended but mandatory, such as the state of Vitoria in Australia, who is now facing the second wave of the virus, which is sweeping through the state like wildfire. Ensuring you have an approved and laboratory tested face mask will ensure the best protection. It’s also important to note that if you are not using disposable masks, where you regularly dispose of the used one and replace with a fresh hygienic new one, then it is relevant to know if the mask was manufactured to the correct certification specifications as well as how to correctly sanitise your reusable masks.


Vapor containing the virus can be introduced into the air by a simple sneeze, cough or simply speaking. Its for this reason that the use of a mask is a smart one! However, simply wearing a mask alone is not the key to eliminating the virus. Regular hand washing is also required to ensure that when you put the mask on and off, that there is no transfer of the virus from your hands to either your nose, mouth or the mask itself.


Relying on social distancing alone can be a concern when you take into account a person sneezing can transmit vapor from their mouth containing the virus and propel it up to 27 feet (8.2 meters) away at up to an astonishing one hundred miles an hour (160.9km/hr).


What other options do we have when dealing with the virus in the air?

Research shows that Ozone gas has been successful in treating the SARS-COV-1, a virus of the same family as COVID-19, the Coronavirus family, which led to the epidemic in 2003.


Ozone is also widely used in sterilizing equipment in hospitals against bacteria as well as purifying the bottled drinking water provided to their patients.


As discussed in a previous article, Viruses-deactivated & destroyed by secondary sanitation technology, COVID-19 is an enveloped virus containing RNA. Ozone can oxidise (destroy) the virus by breaking through its outer layer and damaging the RNA core, rendering it harmless to a potential host (us).


So, what do we know about Ozone gas and COVID-19? Research would suggest that exposure in to a sufficient dose over a given period of time, COVID-19 would be eliminated from open spaces as well as shadows and crevices in the air and surfaces in the treated environment.


Written by: John Morrison BSc




Viruses- deactivated & destroyed by Secondary Sanitation Technology


“Viruses are the smallest of all the microbes. They are said to be so small that 500 million rhinoviruses (which cause the common cold) could fit on to the head of a pin. They are unique because they are only alive and able to multiply inside the cells of other living things. The cell they multiply in is called the host cell.

A virus is made up of a core of genetic material, either DNA or RNA, surrounded by a protective coat called a capsid which is made up of protein. Sometimes the capsid is surrounded by an additional spikey coat called the envelope.”

When it comes into contact with a host cell, a virus can insert its genetic material into its host, literally taking over the host’s functions.

An infected cell produces more viral protein and genetic material instead of its usual products. Some viruses may remain dormant inside host cells for long periods, causing no obvious change in their host cells (a stage known as the lysogenic phase). But when a dormant virus is stimulated, it enters the lytic phase: new viruses are formed, self-assemble, and burst out of the host cell, killing the cell and going on to infect other cells. Viruses attack bacteria, known as the lambda bacteriophage, which measures roughly 200 nanometers.


So, with all that being said, how are viruses treated in our local swimming pools?

If the local pool water is treated with only chlorine (1ppm Free chlorine, pH 7.5 and Temp 26 degrees Celsius), according to the CDC, it takes approximately 16 minutes for viruses to be killed. Viruses are chlorine resistant, meaning they are not easily destroyed by chlorine alone.

Whilst most Australian commercial pools operate at levels higher than 1ppm of chlorine, they also often have water at temperatures higher than 26 degrees Celsius and have the most important variable, pH, to consistently maintain to ensure there is more active chlorine (Hypochlorous Acid) than there is inactive chlorine (Hypochlorite Ion) in the water.

However, if your local pool has a form of ‘secondary sanitation’ equipment fitted to its plant room, which is not reliant on maintaining constant pH levels to be effective, then the risk of a swimmer contracting a virus is significantly decreased.


What is secondary sanitation?

Secondary sanitation is the second line of defense for chlorine (primary sanitiser) and is highly recommended for use on every public pool by the health departments in every state and territory of Australia as it provides the most effective treatment when it comes to the smallest pathogens such as viruses.


What types are there?

There are three main types of secondary sanitisers used, which are listed below from least oxidation potential through to the greatest oxidation potential;

1) Ultraviolet Light (UV)

2) Ozone gas (O3)

3) Advanced Oxidation Process (AOP), which combines UV and Ozone technology to produce Hydroxyl Radicals.


How does Ultraviolet Light (UV) work?

Anne Rammelsberg, a chemistry professor at Millikin University, offers this explanation:

Ultraviolet (UV) light kills cells by damaging their DNA. The light initiates a reaction between two molecules of thymine, one of the bases that make up DNA. The resulting thymine dimer is very stable, but repair of this kind of DNA damage – usually by excising or removing the two bases and filling in the gaps with new nucleotides is fairly efficient. Even so, it breaks down when the damage is extensive.

The longer the exposure to UV light, the more thymine dimers are formed in the DNA and the greater the risk of an incorrect repair or a “missed” dimer. If cellular processes are disrupted because of an incorrect repair or remaining damage, the cell cannot carry out its normal functions. At this point, there are two possibilities, depending on the extent and location of the damage. If the damage is not too extensive, cancerous or precancerous cells are created from healthy cells. If it is widespread, the cell will die.

How does Ozone gas (O3) work?

Ozone (O3) is formed when a high-voltage arc passes through the air between two electrodes. It is also formed photochemically in the atmosphere, and it is one of the constituents of smog. Ozone is a bluish and toxic gas with a pungent odor. Ozone is unstable because it breaks down to give molecular oxygen. Its low solubility and instability require that it is to be generated on site and introduced into the water as fine bubbles.

How does Advanced Oxidation Process (AOP) work?

Conventional oxidation processes are used in water treatment to disinfect water, to reduce toxins, odour and colour or to reduce manganese and iron levels in potable water. These processes may not destroy all toxins and have the potential to create dangerous disinfection by-products (DBPs). Advanced oxidation process (AOP) utilises the strong oxidising power of hydroxyl radicals that can reduce organic compounds to harmless end products such as oxygen.

Oxidation is defined as the transfer of one or more electrons from an electron donor(reductant) to an electron acceptor (oxidant) which has a higher affinity for electrons. These electron transfers result in the chemical transformation of both the oxidant and the reductant.

In advanced oxidation processes AOPs the hydroxide radical, OH not the OH¯ hydroxyl ion as in bases, is produced in a first step. This molecule has a very strong oxidizing and disrupting ability that may, depending on conditions, turn a complex (recalcitrant or refractory), organic molecule into CO2 and H2O.

The first reaction of OH with many volatile organic compounds (VOCs) is the removal of a hydrogen atom, forming water and an alkyl radical (R). OH + RH  H2O + R Oxidation reactions that produce radicals tend to be followed by additional oxidation reactions between the radical oxidants and other reactants, (both organic and inorganic), until stable oxidation products are formed.

AOPs are reactions where first, hydroxyl radicals are produced, secondly, these radicals react with and destroy degradable organic and inorganic compounds. Typically, methods such as Ultraviolet light (UV), Ozone gas (O3), Hydrogen peroxide H2O2, Fenton’s and titanium dioxide TiO2 are combined (synergistic effect) to increase OH formation. Combining methods increases reaction rates 100 – 1000 times compared to using either ozone, H2O2 or UV alone.

Written by: John Morrison BSc



Emiliana, C. Extinction and Viruses. BioSystems 31: 155-159. 1993.

Microbiology Society. Viruses. 2020.

Centre for Disease Control and Prevention (CDC), May 4, 2016.

Scientific American. How does ultraviolet light kill cells? 2018.

Washington University. Why is ozone such a good oxidizing agent? General chemistry lab tutorial. 2001.

Dr Bill Grote. Application of Advanced Oxidation Process (AOP) in water treatment. June 2012.

Department of Health and Human Services, State of Victoria. 2019

Department of Health, New South Wales Government. 2013.

Department of Health, Government of Western Australia. 2020.

Department of Health, Queensland Government. 2019.

Department of Health, Northern Territory Government. 2006.

Department of Health, Australian Capital Territory Government. 1999.

Department of Health, South Australia Government. 2013.


Swimming with Asthma


Is swimming a good activity for young Asthmatics?

It’s well documented that regular swimming activity can be great for those suffering with the medical condition known as Asthma.

“Asthma is a medical condition that affects the airways (the breathing tubes that carry air into our lungs). From time to time, people with asthma find it hard to breath in and out, because the airways to the lungs become narrower – like trying to breathe through a thin straw”.

This is a condition that I in fact suffered at a young age. I would randomly and uncontrollably cough and splutter, which left me gasping and struggling for air at times. This was especially so when my heart rate increased from participating in various types of exercise. And being an active kid who loved sports, this was an ongoing problem and a real handicap. I remember what an amazing feeling and relief it was to breath normally again, thanks to multiple puffs on my Ventolin inhaler.

Compared to other sports, swimming has been found to less likely trigger Asthma. The recumbent exercise of swimming can also produce a greater central blood flow than upright forms of exercise.

Some studies have shown that young asthmatics participating in regular swimming activities resulted in a decrease in the frequency of wheezing days, a decrease in the days needing medication, a decrease in emergency room visits, and an increase in school attendance.

Interestingly, in each of the Olympic Games between 1956 and 1972 there were gold medalists who had Asthma, which just shows not only can you enjoy the benefits of swimming with Asthma, but you can even excel in the sport.

But what if the water quality is poor?

Whether you suffer from Asthma or not, poor water quality can significantly affect your health but especially so for Asthmatics. Some studies suggest that healthy children can have their lung epithelium damaged and promote the development of Asthma as a result of swimming in poor water quality of both indoor and outdoor swimming pools.

What issues with poor water quality should you be concerned about?

Nitrogen trichloride (Trichloramine) is a disinfection byproduct (DBP) produced when chlorine, commonly used as a sanitiser in pools, reacts with urea (ammonia product), which comes from sweat and urine constantly released by swimmers. This chlorine byproduct can cause irritation of a swimmer’s airway, especially if already suffering with Asthma, as well as irritate the eyes.

Haloacetic acids (HAA’s), another DBP formed when chlorine reacts with organic products released by swimmers. Some HAA’s are considered ‘possibly carcinogenic to humans’, according to the World Health Organisation (WHO). 

Are the benefits of the swimming activity outweighed by other risks to one’s health?

It’s no doubt that swimming is a good physical activity for Asthmatics, but only if the water quality is healthy via the correct methods of water treatment that remove not only dissolved chlorine disinfectant byproducts (DBP) but also the gasses too. Such treatment methods include Ozone and Advanced Oxidation Process (AOP).

Written by: John Morrison BSc



Mineral Pools, are they chlorine free?


Mineral Pools, are they chlorine free?

With the craze of ‘mineral’ pools that has hit the pool industry over the last 5 or so years, its important to understand how it all works.

Let’s start with where it all began, the backyard salt (sodium salt) chlorinator. All you had to do was throw in bags of salt and walk away. Ahhhhh that salt water beach feeling! No more manually dosing the pool with chlorine sanitiser either.

Then came along the ‘Mineral’ salt (blends of salts and trace elements, magnesium + potassium + calcium + zinc + copper + iron) chlorinator. It’s driving force the ability of the minerals and trace elements to be dermally absorbed into the skin while swimming to alleviate muscle aches, bring oxygen to the body’s cells, alleviate eczema, relax the nervous system and even soften the water.

Sodium salts or magnesium salts alone are NOT a sanitiser! However, they are both used to make chlorine (sodium hypochlorite), which is a sanitiser.

So how do we make chlorine out of salts? Electrolysis!

The process involves passing salt water (which is a good electrical conductor) through what is called a ‘cell housing’, which houses a cell, made of a series of flat titanium plates coated with iridium and ruthenium and aligned parallel to each other in the cell housing. Electricity is applied to these titanium plates, which separates the chemical bonds of the salts (sodium chlorine/ magnesium chloride) and in the process creates chlorine gas (Cl2), hydrogen gas (h2) and sodium hydroxide (NaOH). The chlorine gas reacts with water (H2O) to form Sodium hypochlorite.

For the chlorinators to work they require specific levels (anywhere from 2500ppm up to 8500ppm) of Total Dissolved Solids (TDS), which a big component of is achieved by the addition of salts. If there is not a sufficient level of TDS the chlorinator will not produce chlorine. If the level of TDS is too high the chlorinator will shut off in order to prevent overload on the cell.

Fresh water chlorination is a whole new kettle of fish! These systems run with very low TDS levels, as low as 1200ppm. They don’t require salt or minerals to be added to the water to produce chlorine, as typically once the pool is filled with water and balanced with chemicals (calcium, alkalinity, acid) the TDS level is sufficient for operation of the fresh water chlorinators to start producing chlorine.

It is a good time to note that a sanitiser level maintained by salt, mineral or fresh water chlorinators (2-4ppm) will not remove inorganic and organic waste products (food source for bacteria), nor destroy chlorine by-products (irritants to the skin and eyes) and does very little for chlorine resistant parasites such as Cryptosporidium and Giardia.

Written by John Morrison BSc



Haloacetic Acids Disinfectant byproduct


Another set of chlorine disinfectant byproduct (DBPs)

Haloacetic acids (HAAs) are formed, along with other Trihalomethanes (THMs) and chlorate, when chlorine is used as a disinfectant in water, which in turn reacts with organic waste products, which are continually being contributed to the water (e.g. by swimmers), to form chlorine disinfectant byproducts (DBPs). This is the exact primary sanitation process that takes place at your local swimming pool.

There are 9 known HAAs, Australia regulates the first 5 of these 9 in drinking water. These levels are compared to that of the World Health Organisation (WHO) suggested levels below:



Health risk

1. Monochloroacetic acid (MCAA)



Group 3

2. Dichloroacetic acid (DCAA)



Group 2B

3. Trichloroacdetic acid (TCAA)



Group 2B

4. Monobromoacetic acid (MBAA)



Group 3

5. Dibromoacetic acid (DBAA)



Group 2B

6. Bromochloroacetic acid (BCAA) Group 2B
7. Bromodichloroacetic acid (BDCAA) <0.1ppm <0.5ppm Group 3
8. Dibromochloroacetic acid (DBCAA) Group 3
9. Tribromoacetic acid (TBAA) Group 3

Below are the International Agency for Research on Cancer (IARC) category group explanations as per scientific studies conducted:

-The category Group 1 is labelled ‘Carcinogenic to humans.’

-The category Group 2A is labelled ‘Probably carcinogenic to humans.’

-The category Group 2B is labelled ‘Possibly carcinogenic to humans.’

-The category Group 3 is labeled ‘Not classifiable as to its carcinogenicity.’

As a result of prolonged exposure to the above HAAs, Increased incidences of tumors in several organs including the liver and kidney, as well as effects to the male sperm and its production were identified in the experimental studies conducted on both rats and mice.

“There are no epidemiological studies of TCA carcinogenicity in humans. Most of the human health data for chlorinated acetic acids concern components of complex mixtures of water disinfectant byproducts. These complex mixtures of disinfectant byproducts have been associated with increased potential for bladder, rectal, and colon cancer in humans [reviewed by Boorman et al. (1999); Mills et al. (1998)].”

Trihalomethanes (THMs) are also regulated in Australia in drinking water, with the limit being <0.25ppm.

A question I am left with is: Why are HAAs and THMs regulated in Australia for drinking water, however they’re NOT regulated in Australia for the commercial pool industry?

Written by John Morrison BSc




Healthy or unhealthy workplace?


“Historically, the heaviest mass inhalational exposures to chlorine resulted from World War I gassing. Currently potential human exposure to chlorine inhalation occurs in a variety of settings in the workplace”. Today’s discussion is the indoor swimming pool!

You know that pungent “chlorine” smell that hits you in the face when you walk into the pool area, it also gets stuck to your skin/hair and swimmers, the sudden shortness of breath, random cough, or maybe the red itchy or dry skin that develops into a rash or maybe that hair loss or those red stinging eyes and even those headaches you get?

Chances are you have experienced one or more of the above during or after swimming, but you shrug it off, just accepting it is all part of the job.

So, say you don’t shrug it off and instead you educate yourself by doing some research; sticking only to credible sources of information. You might come across the following:

“Chlorine species are highly reactive; tissue injury results from exposure to chlorine, hydrochloric acid, hypochlorous acid, or chloramines. Acute, high level exposure to chlorine gas in occupational or environmental settings results in a variety of doserelated lung effects ranging from respiratory mucus membrane irritation to pulmonary edema. Pulmonary function testing can reveal either obstructive or restrictive deficits immediately following exposure, with resolution over time in the majority of cases. However, some of those exposed may demonstrate long-term persistent obstructive or restrictive pulmonary deficits or increased nonspecific airway reactivity after high level exposure to chlorine gas”.

“As with all human and technological intervention, the use of chlorine-based products to disinfect swimming water may lead to a number of unwanted effects, in particular the presence of chlorine-containing compounds in the air. Consequently, chlorination may affect the respiratory health of either those who work as swimming attendants or instructors”.

But let’s say you are just a lifeguard and don’t even get in the water, but you still find yourself developing some health problems. You tell yourself ‘it can’t be the pool; I don’t get in the water’. Well think again!

Research shows whilst you absorb chemical by-products (mono-chloramine and dichloramines) dermally while in the water, you also inhale the gaseous forms of byproducts (tri-chloramines) known as nitrogen trichloride, when reacted with water. They are part of the chlorine by-product group called Trihalomethanes (THM’s).

“Swimming-pool asthma due to airborne nitrogen trichloride can occur in workers who do not enter the water because of this chloramine. The air above indoor swimming pools therefore needs to be assessed and managed as carefully as the water”.

According to Wikipedia, Nitrogen trichloride, trademarked as Agene, was at one time used to bleach flour, but this practice was banned in the United States in 1949 due to safety concerns.

Despite there is plenty of research having been conducted specifically on some health issues associated with swimming pool by-products and their results already published, there is still much more research to be done on other areas of health concerns, which it would seem is also the opinion of our fellow scientists:

“Although the issue of the chlorination of public water supplies has received considerable attention, mainly with regard to the presence of potentially carcinogenic or teratogenic chlorinated by-products, the respiratory hazards of chlorinated swimming water have been less well addressed. Thus, old and even more recent reports on indoor pollution do not deal with the air of chlorinated swimming pools, despite the generally obvious and readily noticeable irritant character of this type of environment”.

Written by John Morrison BSc



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