All chlorine is the same right?  You will be “shocked” that this is not the case.

This is part 2 of a multi part blog series on swimming pool chlorine sanitizers.

What is chlorine exactly?  Thanks for asking!  Hold onto your pool floatie because it is COOL!

Chlorine is a ‘halogen’.  Halogens are a family of naturally occurring elements which include fluorine, chlorine, bromine, iodine, and astatine. These elements are highly reactive and can be toxic to microorganisms. Exposure to potentially harmful organisms in recreational water can cause problems ranging from mild illness to death.

Both chlorine and bromine are used routinely to sanitize recreational water venues. Proper water sanitation is of utmost importance to help protect public health by preventing the transmission of disease.

Sanitation vs. Oxidation

Sanitation refers to killing or inactivating potentially harmful microorganisms. The principal objective of applying any type of sanitizer to a pool or spa is to control the growth of these microorganisms and help prevent disease outbreaks.

Oxidation refers to chemically changing contaminants in the water to make them easier to remove. Routine oxidation is necessary to remove the buildup of organic matter and bather waste.

Types of Pathogens

Bacteria are microscopic, single-celled organisms. Most are harmless, but some can cause serious illness. For example, E. coli O157:H7 is a leading cause of food and waterborne illness. In some people (particularly young children and the elderly), this strain of E. coli can cause hemolytic uremic syndrome which can lead to kidney failure. Another problematic bacterium is Pseudomonas aeruginosa. This organism is spread through contact with contaminated water and can cause rashes or earaches (“swimmer’s ear”). These pathogens are not resistant to chlorine treatment and can be controlled with the proper sanitizer level.

Viruses are genetic material surrounded by a protein coat called a capsid. They are smaller than bacteria and need a host to survive. An example of a virus spread through recreational water is Norovirus, which can cause viral gastroenteritis. Outbreaks are most common in semi-closed communities such as cruise ships. Viruses can be controlled with a chlorine sanitizer.

Protozoa are microscopic, single-celled parasites which are larger than bacteria but too small to be seen with the naked eye. They are typically more resistant to halogen sanitizers. Cryptosporidium parvum, for example, is protected by an outer shell which allows it to survive in a halogenated environment. Cryptosporidium parvum is spread by swallowing contaminated water and can cause gastrointestinal distress.

Contact Time

Contact time (or CT value) refers to the concentration of the killing agent in relation to the time the microorganism.

is exposed to that killing agent.  Mathematically, the equation is written as follows:

Contact Time = Disinfectant Concentration (ppm) x Exposure Time (min)

Here is an example – let’s say a certain microbe has a CT value of 10.  This means that 10ppm of disinfectant will kill the microbe in 1 minute.  It also means that 1ppm of disinfectant will kill the microbe in 10 minutes.  So, the CT value remains the same.  If a lower concentration of disinfectant is used, then the killing time will be longer.  Conversely, if a higher concentration of disinfectant is used, then the killing time will be shorter.  The important thing to remember is that microbes with larger CT values are more difficult to kill.

Stay tuned for our next blog on sanitization with chlorine and what that means for you and your family fun.

Got questions, we’ve got answers –

chlorine blog post 2


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