Ozone Treatment of Water
The discovery and benefits of ozone dates back well over 100 years. Recent developments in technology have allowed a new generation of applications and products, using ozone, to emerge.
What is ozone?
Ozone is a very active form of oxygen. It is formed when oxygen is exposed to a high-energy field causing some oxygen molecules (O2) to break down to oxygen atoms (O). The oxygen atoms (O) then react with the oxygen molecules (O2) to form ozone (O3). Notice that this is a reversible reaction meaning that ozone can decompose back to oxygen.
Is ozone found in nature?
Yes, ozone is formed by lightning.
In nature, ozone is produced by the action of lightning on the oxygen found in the air. The formation of ozone leads to the fresh smell that you find outside after a lightning storm. One type of ozone generator, known as the corona discharge type, mimics this natural process in its ozone generating cells.
Yes, ozone is found in the Earth’s stratosphere.
Also, the ozone layer found in the upper stratosphere protects the earth’s surface from harmful UV rays. UV rays cleave oxygen molecules into oxygen atoms which recombine to form ozone. UV rays also excite ozone molecules causing them to breakdown to oxygen to begin the cycle again. In this way, the energy of the UV rays is absorbed by the “ozone layer” protecting the Earth’s surface from their harmful effects. UV-type ozone generators mimic this natural process.
What can ozone be used for?
The very reactive nature of ozone makes it the ideal oxidant for air and water treatment. Ozone will:
destroy bacteria and viruses
precipitate heavy metals (example iron and manganese) allowing them to be filtered
eliminate color from water (for example, like the yellowish colour caused by tannin)
remove rotten egg smell from water (caused by hydrogen sulfide)
oxidise organic compounds to form compounds that can be easily flocculated and filtered or to form water (H2O) and carbon dioxide (CO2).
eliminate bad odor from air
Applications include pool & spa treatment , home drinking water treatment, irrigation water treatment, smoke odour elimination from air, seafood storage… the list goes on and on.
The collage below shows but a few areas where ozone has been used successfully to improve water and air quality and to improve industrial processes.
Water Treatment by Ozone
Ozone Disinfection For Pool Water
Ozone Treatment For Cooling Towers
Techniques for Dissolving Ozone in Water
Ozone can be dissolved in the water using the following techniques:
This is a simple method diffuser is used for bubbling ozone through the water. The diffuser is connected to the output of the ozone generator.
Online Venturi Injection System
This method is more efficient as compared to the diffuser. In this method the Venturi injector is placed on the main supply line. Just after the Venturi static mixer is installed for the better results. The differential pressure across the Venturi should be atleast 1.0-1.5 kg/c.m for efficient working of the Venturi. For better mixing and absorption the differential pressure must be kept higher.
This method uses recirculation pump, Venturi injector, static mixer, tank diffuser and single pass or multiple pass ozonation tank. In order to provide a counter current flow of ozone and water, the water enters the ozonation tank from the top. The use of separate loop ensures the better mixing of water and ozone.
Pressure Booster Injection System
This is a latest innovation that increases the dissolution efficiency. The pressure differential is created between the inlet and the outlet of the Ventury injector for the ozone injection. The system consist of by pass branch header line with a booster pump, Ventury injector, static mixer, booster pump etc.
A typical ozonation system consist of following components:
Ozone generator is an engineering product that produces ozone molecules for disinfecting water. These generators produces ozone molecules from various methods like corona discharge tube, ultraviolet light and cold plasma.
Ozone contactors with bubble diffusers are used for dissolving ozone into water. These diffuser creates bubbles that transfer the ozone into the liquid phase. The advantage of this bubble diffuser contactors is that, without any additional energy input they can use the pressure of the ozone generator to drive the gas through the diffusers. There is a series of deep multi chamber basin in which the diffusers are located.
Side Stream Injection
This system is splits main flow into a side stream in which the Ozone is injected and then the side stream is mixed into the main flow. The whole system comprises of booster pump, a venturi and nozzles that helps in the introduction of the side stream back into the main flow.
the other components of ozonation system are feed gas system, feed gas system ozone reaction system, ozone controller and concentration monitor, vent ozone destructor and control system.
Advantages Of ozone treatment
Ozone act as the strongest and most effective agent for disinfecting water. The advantages of using ozone in water treatment are:
For powerful germicides like faecal bacteria they act as strong germicides.
By breaking organic constituents, it reduces turbidity of water.
Whole process can be controlled easily. The process is easily controlled.
In the process no chemical is added to the water.
All the inorganic, organic and microbiological problems can be eliminated by ozonztion
It very effective against coliform bacteria and destroys them much faster than chlorine or bromine.
PH can be neutralized by them very easily.
Helps in the destruction of fungus, mold and yeast spores.
All heavy metals are precipitated by them easily
It is capable of conditioning the water naturally without the addition of any chemicals. Water conditioning is achieve by removing excess iron, manganese, and sulfur.
Water color an odor is effectively removed by ozone generator.
There is no scale build up on pipes and water heaters thereby reducing the instances of stains on showers, sinks, bathtubs and toilets.
There is no residue left by it as its byproduct is pure oxygen.
Strongest oxidizer and disinfectant commercially available
Decomposes into harmless oxygen
Ozone reacts with a large variety of organic compounds
Generated and used at point of use
Kills bacteria over 3,000 times faster than chlorine
The applications of ozone span a variety of topics and industries.
Used as a replacement for chlorine and bromine in swimming pools, Ozone is a very effective disinfection agent which even prevents the formation of chlorine and bromine byproducts. For soil remediation, Ozone has been used to clean up sites containing a variety of soil contaminants, including oil and fuel.
Because it’s highly reactive and unstable, ozone does not persist—any ozone not instantly consumed by contact oxidation of organics quickly reverts to oxygen. This makes ozone perfect as a final, no-rinse sanitizer. With no persistence, ozone requires no special disposal system.
Comparison of Various Disinfection Technologies
Ozone Treatment of Water