Since ozone’s discovery in 1785 by Martinus van Marum, and later being named after the Greek word ozein (“to smell”) by Christian Schönbein in 1839, ozone has been touted as a miracle gas with a wide range of uses. It’s been referred to as a medical treatment for everything from skin disease to arthritis to heart disease.
I’m a bit of a sceptical guy though, and I believe that when something sounds too good to be true, it often is…So from my frame of reference as a water treatment service provider, I must admit to having at first taken the use of ozone in water treatment “with a pinch of salt”.
I mean, when I’m told that there’s an easily available, naturally occurring, powerful form of disinfectant which only uses a little bit of electricity to produce a potent disinfecting gas out of the oxygen which is all around us, which doesn’t require hazardous chemicals to be monitored and refilled, and will do the same job as chlorine, but up to 3000 times faster and with over 1.5 times the power, who wouldn’t be a bit cynical?
But as it turns out, ozone is an extremely useful tool for water and air disinfection.
The fact is, it’s used by farmers the world over to make sure their irrigation pipes stay clear of biofilm (the slime caused by bacteria that blocks up the system over time).
It’s used in the cold rooms at our biggest chain store distribution centres, to ensure that those vegetables we all eat are free of pathogens, and to keep those veggies fresh for as long as possible.
Ozone is used by water bottling companies and cooldrink manufacturers like Coca Cola, all over the world, to make sure that the beverages they sell are free of bacteria and fresh tasting.
In water treatment, it’s used to oxidise and remove iron, manganese and tannins in groundwater, as part of pre-filtration.
So how does it work?
Ozone works in a similar way to chlorine, in that it’s an oxidant. Ozone is produced from breaking down an oxygen molecule (O2) into two single oxygen atoms, which then recombine into an unstable three-atom oxygen molecule (O3).
As this ozone molecule is unstable, the extra oxygen atom will take the first opportunity it gets to hook up with (oxidise) another molecule.
For disinfection, oxidation means that it breaks down the cell wall of the organism, in a process called “lysis” which causes the cell wall to rupture and the bacteria or virus is physically destroyed.
If one compares ozone disinfection to disinfection by UV-C light, UV works by interfering with the cell’s RNA structure, which stops it from reproducing, while ozone destroys the cell.
So while disinfection is one result of ozone’s oxidation ability, it can be used to oxidise other contaminants in the water as well.
Iron oxidation is where iron is converted from its dissolved “ferrous” state, into the solid rust particles we see (and can then filter out) in a “ferric” state. So if an iron molecule and the ozone molecule meet, the extra oxygen atom reacts with the iron molecule and dissolved Fe2+ iron becomes the solid, ferric form in water as Fe(OH)3, which can be filtered.
It does the same with manganese, but more ozone is needed to do this job, as well as assist with tannin reduction. We know that iron needs 0.43 mg/l ozone to oxidise 1 mg/l iron, and manganese needs 0.88 mg/l per 1 mg/l manganese, so systems are sized accordingly. There’s a calculator here to help give an idea of the amount of ozone required.
Tannin is the colour in the water which is caused by organic matter such as decayed leaves, and ozone can be used in the removal process.
Ozone has some coagulant abilities and it helps to collect the fine colloidal particles floating in the water which would otherwise be too small to be caught by a filter, into bigger particles which can be filtered, or will settle to the bottom of a tank (flocculation).
Ozone can be generated on-site and added to the water, so it’s an easy way to ensure clean, disinfected water with no chemicals needed.
Swimming pool systems can be converted to ozone. The water is much kinder on the skin and lungs than chlorinated pool water.
The problem with chlorinated water is not the chlorine itself, but the chloramines which are formed when the chlorine combines with ammonia in the water. It’s the chloramines that cause the red eyes, skin irritations, respiratory problems, and give that typical “chlorine” swimming pool smell.
People who spend a lot of time in and around pools (like competitive swimmers, swimming coaches and maintenance staff) enjoy immediate benefits when changing to an ozone disinfection system.
Ozone has been used for primary disinfection in the Olympic swimming pools since 1996, rather than chlorine, for good reason.
There is a caveat to ozone-treated swimming pools though. Ozone has a short half-life, typically less than 30 minutes in water at 20°C, which means that it doesn’t stay in the pool water very long to provide much residual disinfection. Chlorine and bromine are active for much longer and for that reason it’s suggested that a small quantity of one of those are used in addition to the ozone. Bromine is often used together with ozone as it forms bromate, which is a long-lasting residual disinfectant.
If chlorine is used together with ozone, ozone does the “heavy lifting”, and much less chlorine would be used, just to provide a residual. Chlorine use is typically half of that used previously, without the chloramines.
Besides the fact that ozone works so much faster than chlorine, it has one incredible feature that sets it aside from any other disinfectant – when ozone has done its work as an oxidant, it reverts back to oxygen, leaving no trace of environmentally hazardous chemicals behind.
Replacing chlorine with ozone has these immediate advantages:
- No constant buying of chlorine or other chemicals
- No unwanted disinfection by-products
- Ozone is produced on-site using oxygen from the ambient air, or can be produced more efficiently using an oxygen concentrator or bottled oxygen
- It works quickly, much faster than other oxidants
- It reverts back to oxygen when it’s done its disinfecting work
One just has to look at this chart of the results of an ozonation system, taken from one of our remote monitoring customers, to see how quickly ozone raises the ORP (Oxidation/Reduction Potential) reading. There is no question that ozone works, and it does it quickly with no side effects.
If you’re interested in a chemical-free alternative for disinfection, contact us to find out more about an ozone system to fit your needs.