Water Treatment by Ozone

How does Ozone in a Swimming Pool work

Ozone oxidises combined chlorine and bromine, freeing them to be continuously re-used. Therefore the use – and cost – of chemicals is greatly reduced.

Ozone destroys algae, viruses and bacteria on contact – with no harmful by-products. It also breaks down harmful chemicals and acts as a flocculent, causing Total Dissolved Solids to be suspended and easily removed by the water filtration process.

Ozone gas

Ozone gas is basically an active form of oxygen that reacts with bacteria, viruses, algae, and other impurities in the water.  At its low concentration levels in the water it has no effect on your skin and eyes. 

Many municipal water purification plants use ozone to treat drinking water. 

When the ozone gas dissolved in water comes in contact with impurities it oxidizes them as chlorine chemicals do. It also causes particles, body oils, and suntan oils, etc. to clump so the filter can remove them more effectively.   

Most ozone purifiers for pools and spas use only about 0.5 amperes when they are running. This is about the same amount of electricity a 60 watt light bulb uses. Since the ozone generator unit only runs when the filter pump is operating the total amount of electricity used is not great.

Ozone Generators

The ozone kit is installed in the existing pool or spa filtration plumbing. There are several basic designs of ozone generators but they all inject the ozone gas into the pool water through a small tube. 

The concentration of ozone gas is strongest at the point of entry for effective purification. An ozone system is not actually "no-chemicals" because you will still need to keep a very low residual level of chlorine in the pool water. 

This is generally only about 20 percent as much chlorine as when no ozone is used. The two basic types of ozone generators are ultraviolet (UV) and corona discharge (CD). 

UV systems use a fluorescent light to create ozone as the sun does above the earth.

CD units use an electrical arc inside a generator to create ozone as lightning does (the fresh smell after a storm). Ozone is the most powerful oxidizer that can be used in a pool or spa, but in most cases you will need to supplement with chlorine.

What is Ozone?

Ozone has been around since the beginning of time. Also called tri-atomic oxygen, ozone is a molecule consisting of three atoms of oxygen, formed when oxygen molecules are broken apart and rejoined again.

The ozone layer in the stratosphere that seems to have an ever widening hole over Antarctica is a 6 mile thick layer of tri-atomic oxygen.

The ozone molecule is a very powerful oxidizer and sanitizer. It destroys anything it comes in contact with, faster and more effectively than anything else available. And when the sanitation is complete, or if ozone finds nothing to oxidize, it returns to molecular oxygen (2 oxygen atoms).

How it is produced in the Stratosphere

Ozone is produced in the stratosphere by two methods.

 UV radiation from the sun will break apart molecular oxygen into individual nascent oxygen atoms. These atoms quickly attach themselves to the first molecule they encounter. When they join with an oxygen molecule, tri-atomic oxygen (ozone) is born.

Another way in which ozone is created is through lightning, corona discharge, occurring in the stratosphere. The electricity breaks apart the molecules and rejoins them in the same manner as UV radiation.

Ozone is produced for swimming pool water in these two methods. In the UV method, air is passed over a UV bulb, and the radiation creates nascent oxygen and then ozone. The molecules are then introduced into the water where they can do their stuff. In the corona discharge method, a small lightning storm is created in an air filled chamber.

Ozone is a sanitizer, but also a gas

Ozone is indeed a powerful sanitizer, but it is a gas.

It is not marketed as a stand alone technology simply because of the production required to have ozone molecules visit every square inch of your pool before it is changed into something other than ozone. In other words, we still have problems with the short life span of ozone, and the distribution of it. Ozone is also not very effective on algae, so a bottledalgaecide or Potassium Tetraborate is necessary.

However, ozone will continue to grab market share for pools. It gives water a better smell, taste and clarity than chlorine alone, and because it produces no byproducts, it doesn't contribute to TDS. Ozone removes certain dissolved metals and rids the pool of soaps, scum, oils and chloramines. It also has synergy with halogens, meaning that when combined, they work even better on certain micro contaminants.

Ozone Chemistry

Ozone is generated when a molecule of oxygen is illuminated by high energy ultraviolet light.

Ozone is formed when three atoms of oxygen are bound together instead of the normal two. The extra oxygen atom makes ozone a highly energetic oxidiser.

Ozone destroys algae, viruses and bacteria on contact – with no harmful by-products. It also breaks down harmful chemicals and acts as a flocculent, causing Total Dissolved Solids to be suspended and easily removed by the water filtration process.

Ozone oxidises combined chlorine and bromine, freeing them to be continuously re-used. Therefore the use – and cost – of chemicals is greatly reduced.

In the process, ozone biologically destroys bacteria, virus and algae and oxidises metals which bond together for easy removal by the filter


What is Ozone?

Ozone is active oxygen, O3. It occurs naturally in the earth's atmosphere to protect us from the sun's harmful rays.

What are some uses of ozone?

Some common uses are: pool and spa water purification, drinking water purification, waste water purification, and air freshening.

How long has it been used to purify water?

Since the late 1800's.

How long has ozone been used to purify pool and spa water and remove odors from the air?

Over 50 years.

How does the ozone used for water purification affect the air we breathe?

The amount of ozone produced by an ozone generator is insignificant to the normal atmosphere we live in. When dissolved in water, ozone is extremely safe. Excess ozone quickly converts back to oxygen. Note: Do not breathe concentrated ozone gas.

Is ozone the same as "SMOG"?

No! "Smog" is air pollution created by combustion polluters. While smog contains small amounts of ozone, it is largely composed of harmful chemicals such as carbon monoxide. In fact, smog and other pollutants may contribute to the damage of the ozone layer.

If I use ozone in my pool or spa, will I help replenish the ozone layer?

No. Because ozone reacts so quickly with contaminants in water and air, it converts back to oxygen within minutes or even seconds. Any ozone molecules that break free from the pool or spa water will convert to oxygen and never reach the atmosphere.

Will ozone hurt me?

No! In the quantities necessary to be effective, ozone is very gentle to humans and equipment in the water. However, you should never breathe concentrated ozone gas.

Does ozone have an odor?

Yes. Depending on the concentration, the odor ranges from slightly sweet to moderately antiseptic.

Will ozone kill bacteria?

Yes. It is one of the most effective, complete bactericides of all earth's measurable elements.

Will ozone kill viruses?

Yes. Ozone kills virtually all known forms of viruses in water and air.

How is ozone different from chlorine?

In the quantities needed for water purification, it has no noticeable odor, taste or color. It is not irritating to humans or equipment. Ozone purifies water and air very quickly and efficiently, 3,000 times faster than chlorine. Ozone leaves no by-products except pure oxygen. In contrast, chlorine leaves a chemical by-product called hypochloric acid and additional salts in water applications.

Will Ozone reduce scum lines and foaming in spas?

Yes. With proper filtration it should completely eliminate them.

How is ozone produced?

Ozone can be produced by ultraviolet (UV) light or by corona discharge (CD).

How does ultraviolet light ozone generation work?

A special lamp gives off a specific wavelength of ultraviolet light which converts oxygen (O2) molecules into ozone (O3) molecules by splitting the oxygen molecules into individual oxygen atoms (O1) which then recombine with oxygen molecules to form ozone. This all occurs instantly inside the ozone chamber in the ozone generator.

How does Corona Discharge Ozone Generation work?

Ozone is produced by passing air through a high voltage electrical discharge, or corona. A minimum of 5,000 volts of electricity is necessary to create the corona. Air or concentrated oxygen dried to a minimum of -60°C dew-point passes through the corona which causes the O2 bond to split, freeing two O1 atoms which then collide with other O2 molecules to create ozone. The ozone/gas mixture discharged from the CD ozone generator normally contains from 1% to 3% ozone when using dry air, and from 3% to 6% ozone when using high purity oxygen as the feed gas.

Can ozone damage my pool or spa equipment?

No. In fact, it is very gentle to spas, pools, and equipment. Applied properly, ozone is more gentle than any other water purifier in existence.

Can the ozone in my pool irritate skin or eyes like chlorine in pools?

No! Ozone is very gentle to skin and eyes.

How long will ozone last in my pool or spa water?

Scientific theory states that Ozone has a half life of about 22 minutes in water. In residential applications, ozone reverts back to oxygen in minutes (ozone breaks down faster in warmer water)

Will water temperature affect ozone?

Wide variations in pool water temperature will affect how well ozone works. An ozone generator should be designed and sized for maximum water temperatures and bather load.

Will ozone affect my pH?

Ozone is pH neutral. It will not adversely affect the pH.

Do I still have to filter the water as often?

Yes. Because impurities are constantly being introduced into the water and the ozone is constantly destroying them, the microscopic remains will need to be filtered out of the water.