About Ozone

While many consumers frequently refer to ozonation as an "alternative sanitizer," is both a sanitizer and oxidizer. It also is the only treatment other than chlorine compounds that is approved by the U.S. Environmental Protection Agency (EPA). Remember, oxidation and sanitation are critical to proper pool and spa water treatment. Failure to consider both of these can result in the growth of pathogens that induce problems such as itchy skin and life-threatening illnesses.

Pool and spa water can have excellent clarity, no odor or taste, and still be contaminated with bacteria, viruses and fungi. True water sanitation can only be judged by various chemical and biological tests.

The public health department usually sets levels for bacteria that it considers safe. Typically, a sanitizer is defined as an agent that can kill 99.9 percent of all growing bacteria.

Billions of bacteria are introduced to pool or spa water each time a bather enters. Outdoor pools and spas also may be contaminated with various pathogens, pyrogens and nuisance organisms.

Ideally, kill time will be short (30 seconds or less) and sanitizer concentration low. Chlorine and ozone meet these criteria.

"There is no single agent that will act as an ideal sanitizer" Several factors influence a sanitizers effectiveness, including concentration, intensity and nature of the sanitizer; kill time; type and number of organisms to be removed; pH; and organic loading. It should come as no surprise that there is not one consummate sanitizer (or product) for each factor listed.

"Oxidation is frequently overlooked in the treatment of pool and spa water" As a general rule, 90 percent of chlorine or bromine in a pool or spa is used to oxidize organic loading (which forms chloramines) and inorganic loading (which can form carcinogenic or pyrogenic compounds).
Technically, oxidation is the process of electron transfer. Atoms or molecules that lose electrons are oxidized.
Think of it in simpler terms: Just as fire reduces wood to ashes, oxidizing agents in water reduce organic loading to carbon dioxide and water. The oxidizer is like the oxygen that feeds the fire and allows it to burn.
The oxidation of organic and inorganic compounds is important for a variety of reasons.
First, sanitizers are neutralized by organic matter in the water. For example, the oxidation of ammonia by chlorine results in chloramines. This depletes the chlorine reserve and causes many undesirable effects, such as odor.
Second, organic matter can provide protection to the very pathogens you want to kill. Their cell coatings can act as barriers to sanitizers that try to disrupt cellular metabolism.
Finally, organic matter provides nutrients that pathogens and nuisance organisms need to reproduce and grow.
Inorganic compounds, pyrogens and metals can cause staining and corrosion as well as reactions that are harmful to bathers. Oxidizing inorganic compounds, pyrogens and metals reduces them to inert compounds that either precipitate or coagulate. Then, the filter can remove them.
Some studies show ozone may be the most powerful oxidizer and sanitizer readily available. Despite this, ozone still is not a stand-alone solution in pool and spa water treatment.
Ozone is very unstable, but this instability also gives ozone its potency and quick reaction time (on the order of 1/10 second with organic contaminants and pathogens).
This high reactivity also causes ozone’s only real drawback - it’s impossible to establish an ozone residual without considerable expense. The typical European corona discharge-type installations don’t comply to the DIN standard or achieve an ozone residual in the pool.
Instead, try using chlorine or bromine as a residual sanitizer and inject ozone via a bypass venturi (commonly called sidestream injection).

"Bacteria and other microorganisms cannot develop a resistance to ozone" There are three primary reasons why ozone is a powerful sanitizer. It is non-selective, it kills by rupturing the cell membrane (also called cellular lysis), and it has a short reaction time.
The term "non-selective" means that ozone will react with any pathogen it contacts. This is not the case with all products termed "alternative sanitizers."
Pathogens cannot develop a resistance to the method by which ozone kills (lysis). In the case of organisms such as algae, ozone only destroys the creatures’ ability to reproduce, and they cannot develop resistance.
Most alternative sanitizers kill by entering the cell and interfering with metabolic processes - essentially poisoning them. Like bacteria that have developed a resistance to antibiotics, most organisms can develop a resistance to those alternative sanitizers.
Before examining the final factor, take a look at how microorganisms die in the presence of a sanitizer.
When exposed to a lethal dose of any sanitizer, microorganisms are killed in equal percentages per unit of time. Therefore, the effectiveness of a sanitizer can be correlated directly to sanitizer concentration (known as a "CT value" in the drinking water industry) and varies from organism to organism.
Ozone is pH neutral. Changes in pH will not degrade its performance and, conversely, it will not affect the pH of the pool or spa.
Considering these factors, ozone is a potent oxidizer. We have found that the time required to kill most pathogens in the pool or spa, in conjunction with chlorine or bromine, will be approximately a few seconds at ozone concentrations of 0.1 - 0.3 mg/L.
Although ozone is a powerful sanitizer, it primarily acts as an oxidizer in the pool and spa environment.
Bather or organic loading exerts an ozone demand that can only be overcome in the bypass loop, which is one of the reasons why ozone should be used with chlorine or bromine.
Ozone reactions result in several outcomes. Simple molecules will be broken down into carbon dioxide and water.
More complex molecules may be broken down into a variety of configurations that precipitate and are removed by filtration.
Byproducts of these reactions may be other oxidants (i.e., hydroxyl radicals, etc.) that can cause further reactions. In short, an initial reaction of ozone with organic molecules may cause dozens of sub-reactions that also are beneficial.
Finally, we find that when used with chlorine or bromine, ozone reacts with the combined forms (i.e., chloramines and bromamines) to produce the free forms of these halogens (hypochlorous or hypobromous acid0 that act as the residual sanitizer.
There are several results from these reactions. First, the oxidation of organic loading deprives pathogens of a primary source of nutrients. Second, it eliminates a potential source of protection (organics can coat a cell and inhibit some sanitizers).
Third, it increases the oxidation reduction potential of the pool or spa water, commonly called ORP.
ORP is measure in millivolts and is a measure of the sanitation/oxidation capability of the water. A reading of 650 mV is commonly considered a nominal minimum for the inactivation of pathogens. This can be achieved by combining ozone and a halogen

"Ozone is an oxidizer and sanitizer, not an alternative sanitizer"
In summary, ozone acts primarily as an oxidizer in the pool and spa environment. It acts as the primary oxidizer when used with chlorine or bromine, thus allowing those chemicals to operate more effectively as sanitizers.
While ozone contributes to sanitation in this role, it is not its main function. So the next time you are discussing ozone, think in terms of oxidation and sanitation, and leave the term "alternative sanitizer" on the shelf.

Contact Prozone Water Products for more information