Ozone
Due to its oxidation and disinfection capabilities, ozone has many uses in water treatment.
Think of ozone as oxygen’s hyperactive cousin. Molecular oxygen is a stable molecule consisting of two atoms (O2), while ozone is unstable and has three oxygen atoms (O3). It’s this instability which gives it its great oxidation and disinfection powers.
It can be used to oxidise iron, manganese, hydrogen sulphide and tannins during the filtration process, and it’s used as a disinfectant for treated water.
It has a very short half-life and breaks down rapidly. Any ozone not used for oxidation or disinfection returns to oxygen, within minutes.
Rainwater tanks are extremely vulnerable to pathogens, due to the nature of the collection area. These can originate from the droppings of birds, squirrels or other rodents, and geckos or other animals making their way into the tank or in the gutters.
If one is collecting rainwater for use in the house, the system should be sealed as much as possible, with the minimum of a leaf catcher on the gutter downpipe and preferably a “first flush” diverter to keep larger debris out of the tank. Even with good pre-filtration though, it’s easy for bacteria, viruses or protozoa to get into the tank.
Ozone is a great choice for disinfection as it doesn’t produce the same unwanted disinfection by-products as chlorine does. It’s a much stronger and faster-acting disinfectant than chlorine, and it kills chlorine-resistant pathogens like cryptosporidium and giardia protozoa.
It’s not as affected by suspended solids (turbidity) in the water as a germicidal UV light is, and it actively helps to improve the clarity of the water in the tank by assisting with the coagulation and flocculation process. This allows suspended solids to settle to the bottom of the tank, or to be more easily removed during filtration.
Not only does it disinfect the water, but it acts to oxidise metals and organic pollutants as well, which helps to improve the odour and taste of the water.
Ozone is unstable and it can’t be stored and transported, so it’s generated on-site by using an electrical process to convert oxygen to ozone.
The ozone then needs to get into the water, and this is achieved either by bubbling the ozone into the tank water with an air stone or with a venturi.
The air stone “bubbler” system runs on a timer, and the unit will switch on and off intermittently during the day. It’s a quick installation and a great way to get “peace of mind” that the water you’re using in the house has been disinfected.
Ozone in Swimming Pools
We also use ozone to disinfect swimming pools. It doesn’t completely replace chlorine, but it will significantly reduce the chlorine requirement. A reduction of between 50% and 90% in chlorine use can be expected. Ozone has a very short half-life, and to make sure that all areas of the pool are protected, it’s advisable to still maintain a small amount of free chlorine.
When chlorine reacts with ammonia in the water it forms chloramines, which cause the red eyes, skin irritations, respiratory problems and typical pool smell which goes with a chlorinated pool. By using ozone, the chloramines are reduced, and the water is easier on the skin, eyes and lungs. Ozone is a good choice for pools which see a lot of use – swimming schools, public pools and school pools.
Swimming trainers and other people who spend a lot of time in the water will enjoy the benefits of lower chloramine levels.
Ozone generators are sized according to the size of the tank, pool, or the intended use. Contact us for details on which system will be appropriate for your needs.
Ozone is used as part of the process in removing iron from borehole water:
