Table 4: Ozone effectiveness against common pool micro-organisms |
||||
|---|---|---|---|---|
| Micro-organism | CT Value (ppm minutes) | Per cent inactivation | Temperature | pH |
| Cryptosporidium | 3-10 | 99 | 25 C (77 F) | 6-7 |
| Giardia lamblia | 0.5-0.6 | 99 | 5 C (41 F) | 6-7 |
| Adenovirus | 0.9 | 99 | 25 C (77 F) | 7 |
| E. Coli | 0.02 | 99 | 5 C (41 F) | 6-7 |
| Legionella pneumophila | 0.05-1.5 | 99 | 25 C (77 F) | 7 |
Oxidation is necessary in pools because the organic contaminants consume the sanitizer, make the water cloudy, and potentially pose health concerns with accidental ingestion. Generally, ozone does a better job than chlorine at eliminating organic contaminants because it is 2.2 times more powerful as an oxidizing agent than hypochlorite (ClO−).
Like chlorine and UV, ozone is very effective at chloramine destruction and microbial inactivation. For chloramine destruction, ozone’s mechanism of action is the oxidation of the chemical bonds leading to chloride and nitrate formation. For microbial destruction, ozone’s mechanism of action is oxidation of the cell wall or membrane of the micro-organism, leading to cell leakage and ultimate cell death.
With respect to most bacteria and viruses, less than 1 mg/L (1 ppm) of ozone is needed for a 99 per cent inactivation (see Table 4). Analogous to chlorine, the sensitivity of micro-organisms to ozone is measured by ozone’s CT value—ozone concentration multiplied by the exposure time. Unlike chlorine, however, ozone does not provide a long-lasting residual and, therefore, cannot be used as the primary sanitizer. Owing to its disinfection and oxidation capabilities, ozone makes for a logical complement to chlorine.
The benefits of UV and ozone as destroyers of chloramines and micro-organisms are not lost on major international authorities on water sanitization, including the CDC, EPA, and WHO. All of these organizations recognize and recommend UV and ozone as supplementary technologies to chlorine for drinking water and pool water treatment.
Taking UV and ozone to another level
Microbial inactivation studies, employing a combination of UV and ozone, have been reported for decades in water treatment.
In these research investigations, which span multiple water treatment applications, researchers have observed a synergistic effect when UV and ozone are used in combination for disinfection and oxidation purposes. That is to say, the observed results were greater than the expected contributions of their parts. The synergistic action, as observed by many investigators, has been attributed to the formation of hydroxyl radicals when UV light interacts with ozone. The use of hydroxyl radicals in water treatment is commonly referred to in scientific literature as ‘advanced oxidation.’
Ozone has to be removed before going back into the pool. UV really does not have an application in swimming pools or spas due to the turbidity of the water. Before taking a leap into ozone or UV read ALL the positives and negatives regarding the system. Do not attempt to apply single pass drinking water regulations for UV and follow the Ozone mfg recommendations on Linked In. Ozone is not allowed in pool or spa water it must be removed by GAC granular activated carbon.