Ozone is used to supplement disinfectants like chlorine or bromine in pool or spa water. Ozone (O3) is a colorless, odorless gas used for water sanitation. Ozone consists of three atoms of oxygen and is a highly reactive form of oxygen. Ozone is one of the strongest known oxidizers, capable of annihilating organisms by cutting open the cell wall, a process known as cell lysing. Ozone is used to purify water by oxidizing contaminants.
Contents
- How is Ozone Produced?
- What is an ozonator?
- How to Measure Residual Ozone in Water?
- What are the Limitations of Hydroxyl Radicals and Ozone in Pool Water?
How is Ozone Produced?
Ozone can be produced through two methods: UV and CD. In the UV method, UV rays split an oxygen molecule into two oxygen atoms. The unstable oxygen atom combines with any nearby oxygen molecules, resulting in ozone. This process occurs at a specific wavelength of 185 nm. In the CD method, ozone is generated by a dielectric, which is similar to a car’s spark plug. When electricity is applied, a continuous spark or corona is created. When air containing approximately 21 percent oxygen, or even pure oxygen, is exposed to the corona discharge, ozone is formed.
What is an ozonator?
An ozonator is a device using electricity and oxygen to create ozone and deliver it to a body of water for sanitizing purposes.
How do Ultraviolet Ozonators Work?
Ultraviolet (UV) ozonators work by passing air over UV lamps, which split the oxygen molecules in the air. The resulting oxygen atoms aim for stability. These UV lamps emit light at 185 nanometers (nm) and have been used for years to generate ozone from ambient air. However, UV systems produce less ozone concentration than CD systems.
What is Corona Discharge?
Corona discharge is a method of producing ozone by passing electricity through oxygen and water.
How is Ozone Dissolved in Water?
Ozone is a gas and must be dissolved in water to function. The solubility of ozone in water depends on several factors, including the size of the bubbles, the concentration of ozone, the water temperature, the contact time, the water balance, and the TDS. If ozone is not dissolved into the water, it will not kill and oxidize. For instance, when all the ozone produced created one bubble that burst at the top of the water, not much ozone dissolves in the water. However, when the same amount of ozone produced a million bubbles, a lot of ozone dissolves in the water.
How to Introduce Ozone into Water?
Ozone is introduced into water through several methods including the usage of an air pump and a diffuser stone, employing a special Venturi injector, or utilizing contact chambers that allow 2-4 minutes of contact before returning. In certain setups, ozone is added to a side stream of the circulation system using a separate booster pump. The side stream water is drawn from the main circulation line, post-filter and pre-heater. The ozone is applied to this side stream, and the ozonated water is returned to the main circulation flow. This happens after the water has passed through the heater, but before any additional disinfectants are injected into the water.
What is the role of Ozone in water treatment?
In water treatment, ozone directly oxidizes or eliminates contaminants such as chloramines, combined chlorine, disinfection by-products, organic materials, microorganisms, and micro-contaminants. Ozone also decomposes into the significantly more potent hydroxyl radical (•OH), which rapidly oxidizes and decomposes organic materials.
How Does an Ozone Unit Impact Water Chemistry?
An ozone unit impacts water chemistry by assisting in the process of flocculation of particles in the water. Through this process, the particles in the water become easier for the filter to remove. However, it is important to note that ozone has a neutral pH and does not significantly affect other water balancing parameters. Regular pool maintenance, such as shocking the pool, brushing and vacuuming, is still necessary.
How is Ozone Introduced in Some Installations?
In certain setups, ozone is added to a side stream of the circulation system. This process uses a separate booster pump. This process is facilitated by a separate booster pump. The side stream water is extracted from the main circulation line after it has been filtered but before it is heated. The ozone is then applied to this side stream. Following this, the ozonated water is reintroduced into the main circulation flow. This reintroduction takes place after the water has been heated but before any disinfectant is injected.
What are Some Additional Ozone Injection Systems?
Besides venturi injection, some systems may use a contact column. This device ensures thorough mixing and extended contact duration, which helps to prevent gaseous ozone from reaching the pool or spa area. In certain setups, ozone is added to a side stream of the circulation system using a separate booster pump. Commercial pools using ozone as a sanitizer require additional equipment, including a contact tank, mixing tower, injector, booster pump, ozone monitors, and other components.
How to Measure Residual Ozone in Water?
Residual ozone in water is measured using test kits, test strips, or electronic probes. However, achieving a residual of ozone is difficult. When a residual is present, it indicates that all oxidizer and sanitizer demands have been met.
What is the Ideal Residual of Ozone?
Some manufacturers recommend maintaining an ideal ozone residual level between 0.01 to 0.05 ppm. However, others emphasize the importance of the dosage level, agreeing that a dosage of 0.1 to 0.4 ppm of ozone is appropriate.
What is the Half-Life of Ozone?
Under laboratory conditions, ozone has a half-life of 3 to 18 minutes. In pool or spa water, ozone lasts from a few seconds up to 30 minutes. This duration depends on the sanitizer demand and the type or amount of other sanitizers or oxidizers used.
What are the Limitations of Hydroxyl Radicals and Ozone in Pool Water?
The limitations of hydroxyl radicals in pool water are that they persist for 10 microseconds or less, which eliminates the risk of any reaching the pool. The limitations of ozone in pool water are that its half-life is influenced by pH and decreases as pH increases. Ozone also reacts with chlorine, making it unavailable for hydroxyl radical generation. In most pool or spa water, ozone’s half-life typically ranges between 5 to 10 minutes.
What Should You Know About Using Ozone in Pools and Spas?
Ozone is used to supplement disinfectants like chlorine or bromine in pool or spa water. However, it is crucial that bathers are not exposed to ozone in the water. UV lamps, available in low and medium pressure output levels, are used in this process. Due to their lower power density, low pressure lamps necessitate a greater number of units to accommodate high flow rates. Medium pressure lamps, despite having a lower effective UV light output, require fewer lamps due to their higher power density. These lamps have a long lifespan, lasting between 4,000 to 9,000 hours.
Can Ozone Stand Alone?
No, ozone cannot stand alone. Ozone doesn’t provide a lasting residual to the water due to its short half-life. Also, the typical concentration, residual, or dosage rates of ozone used in U.S. pools and spas are not sufficient to eliminate algae. Ozone is a highly reactive form of oxygen with three atoms, represented as O3. It is one of the strongest known oxidizers, 25 times faster at killing than hypochlorous acid, the most potent form of chlorine. However, ozone is unstable and reacts immediately, breaking down and leaving minimal residual to combat algae on pool walls. This requires a residual of chlorine, bromine, or another sanitizer. Furthermore, the usual concentration, residual, or dosage rates of ozone used in U.S. pools and spas are not sufficient to eliminate algae. Therefore, ozone does not have the potential to stand alone as a sanitizer in pools and spas.
Why is Ozone Depletion Important?
Ozone depletion is important because all ozone has to be depleted before the circulation water returns to the pool. This is because ozone, being heavier than air, collects at the water’s surface, causing discomfort to the eyes and respiratory systems of swimmers. Therefore, the method of ozone-to-water contact is crucial. Ozone is a highly reactive form of oxygen that is used to purify water by oxidizing contaminants. However, ozone is unstable and reacts immediately, breaking down. When not properly depleted, it causes discomfort to swimmers. It is also important to note that it is not possible for ozone to stand alone because it doesn’t leave a long-lasting residual to the water, given its short half-life. Therefore, it is crucial to ensure that all ozone is depleted before the water returns to the pool.
