Ozone can be used to effectively remove (blue-green) algae. However, there is a big difference between removing filamentous(thread) algae and floating algae with ozone.
People sometimes claim that ozone removes algae by oxidising its nutrition (ammonia and nitrate). However, this is extremely wrong. Ammonia barely gets broken down by ozone, especially at low pH values. It’s effect is only worth mentioning at pH values higher than nine. In that case, ammonia will be converted into nitrate by ozone. Ozone can’t further oxidise nitrate, only bacteria can convert it into nitrogen gas under anoxic/anaerobic circumstances. So to summarise, ozone can only oxidise one of the nutrients of the algae (ammonia) and convert it into another one of its nutrients (nitrate). This shows that removing algae with ozone definitely doesn’t happen by oxidising the nutrients.
The basic rule is that ozone oxidises the algae themselves. A high ozone dose and contact time are necessary though, a minimum C/T value of 1,5 should be taken into account. This means that the algae have to be exposed to an ozone dose of 0.3PPM for five minutes for example. How this should be done depends on the kind of algae that’s targeted.
Floating algae
As the name suggests, floating algae float through the water. This means that a pump can take them through the ozone system. To fight the floating algae, we use reaction vessels so the algae are killed outside the water feature. If the system is dimensioned properly, there will barely be any dissolved ozone in the outgoing water. This makes this technique also suitable for water features that contain fish, such as fish farms and ponds.
Filamentous(thread) algae
This is where things get interesting, thread algae can’t be taken through an ozone system because they are attached to the sides of a water feature. This means that, to fight tread algae, dissolved ozone will have to be in the water feature itself. This also means that this method can’t be applied to water features that contain fish because they can’t stand the necessary concentration of dissolved ozone!
Blue-green algae
The same method to treat floating algae can be used to fight blue-green algae (cyanobacteria). However, the contact time and concentration are different, this has consequences for the dimensioning of the ozone system. The same strategy that’s used for thread algae can also be applied if there are no fish in the water feature.
We’ve got extensive experience in treating algae using ozone. We also have experience with ozone in algae farms. Here, the organisms that ‘eat’ the algae are killed and the algae remain unarmed!
If you have any questions about ozone and its applications, please don’t hesitate to contact us! We’re glad to help!