Ozone is removed from water in three ways: UV radiation, chemicals, and activated carbon.
Ozone (O3) is a naturally occurring gas found in the earth’s atmosphere composed of three oxygen atoms joined together. Also, ozone is much more reactive than atmospheric oxygen (O2) as it contains an extra oxygen molecule. Ozone can also combine with other substances, creating chemical reactions and forming new compounds.
Before we explore how to remove ozone from water, it is important to understand where it comes from and why we use it in water treatment industries.
Where Does Ozone Come From?
According to the Environmental Protection Agency (EPA), it is thought ozone on land comes from pollution such as vehicle exhausts, power plants, and other industrial facilities that emit pollutants like volatile organic compounds.
But we can’t blame these industries, as ozone also comes from our household and office appliances like laundry machines and printers/scanners, basically, anything you own that uses UV light or electrical discharge can contribute to elevated ozone levels.
Ozone In Water Treatments
We use ozone in water treatment industries to ensure drinking water is safe for human consumption. Ozone water treatment processes can be implemented both commercially and in your workplace or home.
Ozone water treatment industries use ozone’s oxidative strength to reduce the number of contaminants in water. As ozone is an oxidant, it can easily react with other substances, picking up electrons in the process.
In ozone water treatments, ozone is injected into the water from an ozone generator. The ozone instantly starts oxidizing and removing contaminants in the water.
Effective over a wide pH range to remove bacteria, viruses, and parasites.
The treatment process is chemical-free, and no pollutants are created during the ozone water treatment process.
It is a tried-and-true technology, originating from the early 1900’s.
Ozone water treatment is a very fast process, sometimes it only takes seconds.
Cons Of Ozone Water Treatment
High-class equipment, operation costs, and system maintenance can be expensive.
There is a possibility that bacteria can regrow, as no germicidal or disinfection process is involved in ozonization.
Special pre-mixing methods are required as ozone is less soluble in water, which is why chlorine is often used to disinfect drinking water.
Because ozone has a short life span, it is very difficult to transport, therefore it is used immediately on site.
As ozone is a toxic gas, any leakages can cause potential hazards to human health. Oxidation by-products are still being investigated for carcinogens.
Potential fire hazards are also related to ozone generation.
Ozone Removal In Water
As mentioned, ozone is used to remove many contaminants in water to improve the water quality, however, the residual ozone concentration must be monitored to keep the water below a certain limit.
Despite ozone’s short lifespan in water, if residual ozone levels exceed the recommended limit (for example, 0.1 to 0.4 ppm in bottled drinking water), corrosion or contamination may occur, therefore, certain measures are taken to reduce or eliminate the residual of ozone.
If methods are not used to remove ozone from water, it increases health and safety concerns.
The three main ways to remove ozone from water are:
Ultraviolet (UV) Light
Using Activated Carbon
Ultraviolet (UV) Light
Ultraviolet (UV) light is an extremely effective way to decompose and destroy ozone in water, which involves a very simple flow-through process.
In high purity water treatment processes, chemical and heat removal is not as successful, therefore in these environments, UV removal is the choice of method to break down ozone in the water.
When Is UV Light Used To Remove Ozone From Water?
Food & beverage industry
Chemicals are added to water to remove residual ozone. The chemicals used include hydrogen peroxide, sodium bisulfite, and calcium thiosulfate.
This method is used to remove ozone from water outside pure water system applications. Adding chemicals to water is widely used in the drinking water industry.
As chemicals can cause potential hazards should they leak, safety sheets must be completed before using chemicals to remove ozone from water.
When Are Chemicals Used To Remove Ozone From Water?
Drinking water treatments
Using Activated Carbon
Activated carbon is perfect when dealing with small amounts of ozone because it is very effective in removing small residuals of ozone from water.
The carbon decomposes residual ozone in water via a catalytic chemical reaction.
When Is Activated Carbon Used To Remove Ozone From Water?
Commercial building heating systems
Ventilation & air conditioning (HVAC) systems
How Long Does Ozone Last In Water?
As already mentioned, ozone has a very short life span in water. It is estimated that ozone only lasts between 1 and 2 hours when dissolved in water, however, ozone will start to decay the minute it is produced.
On average, ozone concentrations will reduce by half after 20 minutes in water.
How To Measure Ozone Levels In Water?
Ozone in water can be measured using a manual ozone test kit or ozone meter. Ozone is measured in ppm (parts per million), and it is easily correlated to the mV (millivolts) reading on an ORP (oxidation-reduction potential) meter to provide you with an accurate ozone reading.
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