Ozone gas is 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 local 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 minimal.
An ozononator 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.
Copper-silver ionization is brought about by electrolysis. An electric current is created through copper-silver, causing positively charged copper and silver ions to form. Copper-silver ionization brings us back to basic chemistry: an ion; an electrically charged atom, has a positive charge when it gives up an electron and a negative charge when it takes up an electron. A positively charged ion in called a cation and a negatively charged ion is called an anion. During ionization, atoms turn into cation or anions. When copper-silver ionization is applied, positively charged copper (Cu+ and Cu2+) and silver (Ag+) ions are formed.
The electrodes are placed close together and the water that is disinfected flows past the electrodes. An electric current is created thus causing the outer atoms of the electrodes to lose an electron and become positively charged. The larger part of the ions flows away through the water, before reaching the opposite electrode. Generally the amount of silver ions at a copper ion rate of 0,15 to 0,40 ppm lies between 5 and 50 ppb. The ion concentration is determined by the water flow. The number of ions that is released increases when electric charges are higher. When copper ions (Cu+) dissolve in water they are oxidized immediately to form Cu2+ ions. Copper can be found in the water in free form. It is commonly known to bond to water particles. Copper (Cu+) ions are unstable in water unless a stabilizing ligand is present. Again, you will need to maintain a modest chlorine residual.
Another alternative is biguanides. Sold under brand names such as Baquacil or SoftSwim, it uses a hydrogen peroxide based oxidizer. It is important that you do not mix biguanides with chlorine. Mixing even a small amount of Chlorine in a Biguanide treated pool can cause extreme reactions. Ever seen an Orange Pool?
Biguanides have lost some of their popularity due to difficulties maintaining pools in various situations. For many pools, Biguanides makes pool chemical care simpler and easier. For some pools, however, there can be issues of cloudy water and persistant algae. Biguanides are also known to gum up your pool filter, requiring annual cleaning of your filter media.