What Ozone Does and DOESN’T Remove From Water

Ozone has the ability to remove hydrocarbons from water.

Ozone water treatment is certainly lesser known than other mainstream treatment methods like chlorination, however, it has certain advantages in that it can interact with both organic and inorganic substances. What substances are resistant to ozonation, or, more importantly, what are some surprising contaminants that ozone can help remove from water? This question led me to look more in-depth into the topic and write this article.

Ozone breaks down both organic and inorganic substances including metals, bacteria & hydrocarbons, however, it cannot remove salt from water. Ozone is a strong oxidizing agent which enables it to break down organic molecules as well as precipitate inorganic materials out of solution.

Ozone Breaks Down Petroleum

Ozone breaks down Hydrocarbons into water, oxygen and carbon dioxide. Perhaps the important fact about ozone and what sets it apart from other effective treatment methods like reverse osmosis is its ability to break down hydrocarbons without any risk to its functionality.  The way ozone breaks down dissolved hydrocarbons efficiently utilizes its powerful oxidation properties in a similar manner to the way it brings metals out of solution. The hydrocarbons which are generally made of a combination of Carbon, Hydrogen and Oxygen atoms are broken down through oxidation and removed from the solution in the form of carbon dioxide, water and oxygen. Ozone is efficient at breaking down all BTEX hydrocarbons (Benzene, Toluene, Ethylbenzene, Xylene) these are common hydrocarbons found in crude oil. An example of how Benze is broken down when oxidized by ozone is highlighted below:

C6H6 + 11 O3 —- > 6Co2 + 3 H2O + 11 O2

Most Microorganisms Are Susceptible To Ozone

Most bacteria and other microorganisms are susceptible to ozone oxidation

Ozone oxidizes fragile cell membranes of microorganisms like bacteria and viruses. The oxidation of cell membranes breaks down the membrane’s semi-permeable qualities leading to intracellular leakage and eventually death. This susceptibility of cell membranes to ozone oxidation is exploited on a mass scale when treating water, sufficient ozone is produced and applied to the water to remove bacteria and viruses from water sources that would have otherwise been unpotable.

The way ozone destroys microorganisms through oxidation is very similar to that of chlorination, although being a stronger oxidant than chlorination it is technically more effective with fewer microorganisms resistant to its effects. I wrote an article comparing these common treatment processes Is Ozonation Better Than Chlorination? 5 Key Comparisons.

Most Metals Are Removed From Solution

Metals are removed from water through ozonation when they are oxidized from a soluble to an insoluble state and then filtered out. Although this doesn’t necessarily work for all dissolved metals, an example of this is when dissolved manganese ions are exposed to ozone they form insoluble manganese dioxide (MnO2) which precipitates as a solid. This solid is easily filtered out of the water, if ozone hadn’t been applied to the water, the dissolved manganese would have flowed straight through the filter so essentially, the ozone enables the metals to be filtered out.

This ability to interact and remove both organic and inorganic contaminants like metals really set it apart from other treatment methods as a complete solution when combined with a simple post-treatment filtration system. There is an article about ozone and its many benefits What is ozonation, and how does it help purify water?

Salt Is Impervious To Ozone

Salt cannot be oxidized out of solution by ozone

Unfortunately, ozone is not perfect, it cannot desalinate water like more specific processes such as reverse osmosis and distillation. Despite interacting with many metals and oxidizing them out of solution, sodium and chloride are both resistant to ozonation. Minor reactions have been observed with Sodium (Na) sporadically forming NaO, however, as a general rule, most salts like Sodium (Na) and Potassium (K) have no insoluble oxidation state/number and therefore cannot be oxidized out of solution in the same way as metals like iron (Fe2+ soluble & Fe3+ insoluble) and lead (Pb3+ soluble & Pb4+ insoluble).

Ozone Does Not Soften Water

In a similar manner to salt, Ozone does not help remove ‘Hard’ ions like calcium and magnesium. Both Calcium and Magnesium have a tendency to leave residual buildups in plumbing, appliances and the human body when they are evaporated out of solution. These buildups cause both annoyance and decreased efficiency, which leads to many households using water softeners to remove them from solution. Calcium and magnesium like sodium and potassium cannot simply be oxidized out of solution in the same manner as iron and lead and therefore ozone has a negligible effect on them. These hard ions do not pose any safety risk, more just annoyance and increased maintenance!

Ozone Helps With Bad Tastes & Odours

Putrid smells are often resolved through ozonation

Bad tastes and odours are often a sign of poor water quality along with just being downright unpleasant. Ozone is incredibly effective at removing or reducing most strange tastes and odours present in water. Most bad tastes and smells coming from water are caused by some sort of contamination, be it organic; like bacteria or inorganic in the form of Sulfur (SO2). As mentioned above, ozone oxidizes organic molecules in the membranes of microorganisms leading to their death, however, it also has the ability to oxidize pungent gasses like sulphur dioxide. Sulphur dioxide is oxidized into pure elemental sulfur which can then be removed from the solution through post-treatment filtration.

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