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What Ozone Does: There are three requirements for proper water sanitation - Disinfection (biocidal action), oxidation and a residual.
Disinfection is the killing of microorganisms such as viruses, bacteria and algae. Oxidation involves the breakdown of nonliving components such as organic and nitrogen compounds (amines). Residual is the amount of free available biocide in the water that ensures the disinfection is fulfilled.
Ozone works as an oxidizer, breaking down or altering nonliving bather wastes or organics such as body oils, suntan lotions, cosmetics and amines, such as urine and perspiration. Ozone also degrades dead algae and bacteria. However, ozone is not a disinfectant and does not provide a residual. As a powerful oxidizing agent, ozone reacts with organics and amines faster than chlorine and bromine. Ozone causes them to break apart into smaller, more water-soluble molecules, which may even gas-off.
Keep in mind that ozone-reacted amine compounds cannot combine with chlorine or bromine to form chloramines or bromamines. This is important because chloramines are responsible for eye and skin irritations with chlorinated water.
Once ozone is introduced into the water, it quickly reacts with nonliving contaminants to produce harmless oxygen, carbon dioxide and heat. The safety limit for exposure to ozone is .1 ppm over an eight-hour period, while allowed off-gassing from ozone generators is less.
Working With Chlorine and Bromine: When chlorine works as an oxidizer in the absence of ozone, the formation of chlorinated organic compounds and chloramines occurs. At this point, chlorine no longer functions efficiently as a biocide. Additional chlorine is then required to establish a sufficient free-chlorine residual, which is known as "superchlorination" or "shocking."
The altered chlorinated organic compounds form scum lines - greases that clog filters and layers with calcium carbonate, resulting in the formation of soft scale. As the chlorinated compounds accumulate, water quality deteriorates and becomes cloudy and dull. Specialty chemicals such as clarifiers, filter aids, pH adjusters, shock treatments, degreasers and scale inhibitors must then be used to improve water quality.
When chlorine and bromine are used in conjuction with ozone as the primary oxidizer, both can act as disinfectants and a residual. Thus, when ozone is used, the homeowner need only add sufficient chlorine and bromine to maintain the safety residual needed to kill the microorganisms.
Ozone and Chlorine Generators: Ozone works well with pools that have chlorine generators. Chlorine generators use electricity to activate the sodium and chlorine components of salt. This process is known as electrolysis. The final products of this process are hypochlorous acid (HOCI), hydrochloric acid (HCI) and sodium hydroxide (NaOH).
Hypochlorous acid is the killing form of chlorine in pool water. Because ozone performs most of the oxidation work in the water, it can increase the capacity of a salt generator to produce a free chlorine residual. Near the plates of the salt generator, a 10- to 40- ppm concentration of chlorine is generated, which is sufficiently high to oxidize bather waste.
Without ozone, at least 70 percent of the sanitizing hypochlorous acid is immediately used up in oxidation reactions and would not reach the pool water to function as a disinfectant and as a residual. However, if an ozone generator is installed in front of the pool pump, the ozone oxidizes out the organic and nitrogen compounds before reaching the salt generator, and 80- to 90- percent of the hypochlorous acid now can enter the pool water and perform its disinfection and safety residual functions.
This allows the salt generator to run at a lower capacity during normal conditions, while extra capacity is available for chlorine production when the pool water is under heavy loads. The expensive plates of the salt generator will last up to twice as long when run at lower capacity, while any pH climb due to generation of the basic byproduct sodium hydroxide is slowed, greatly stabilizing the pool water chemistry.
The combination of ozone and a salt generator produces high water quality with virtually less user intervention. Ozone performs the oxidationfunction while the chlorine produced by the salt generator provides the disinfectant and a measurable safety-backup residual. The pool owner or manager need only control pH and maintain the proper level of salt.
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