Does Reverse Osmosis Remove CO2?

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Carbon dioxide can be added to water either intentionally (by humans) or naturally.

Low levels of dissolved CO2 in water is not harmful but excessive CO2 levels can lead to health complications, which is why you need to find ways of getting rid of it.

So, does reverse osmosis remove carbon dioxide? Not at all.

Although highly effective in eliminating impurities from water, reverse osmosis does not remove carbon dioxide. Removing carbon dioxide from water can be done by ion exchange.

How Does CO2 Get into Water?

Carbon dioxide usually gets into the water through rainfall. As precipitation occurs, water passes through the air with carbon dioxide traces and absorbs some of it.

Additionally, groundwater picks up some CO2 as it flows through organic compounds such as decaying plants.

When carbon dioxide mix with water, it forms carbonic acid, which can cause corrosion in plumbing systems.

To prevent corrosion, you need to neutralize the carbonic acid by running your water through a filter with limestone chips.

The good news is that, in most cases, carbonic acid in water is naturally neutralized when it passes through limestone rock formations.

What are the Effects of CO2 on Water?

Carbon dioxide makes the water more acidic and increases its pH level.

And although low amounts of carbon dioxide in drinking water do not threaten human health, excessively acidic water has been associated with the erosion of bones and teeth.

High levels of carbon dioxide in water can also lead to digestive issues and corrosion of plumbing systems, as aforementioned.

Excessive carbon dioxide in water can also cause harm to other living creatures like fish.

How is CO2 Removed from Drinking Water?

You can remove carbon dioxide from drinking water using the following:

  • Limestone Chips

The simplest method of removing carbon dioxide from water is passing the water through a tank with limestone chips.

The limestone in the chips reacts with carbonic acid (a mixture of CO2 and water) to produce calcium bicarbonate.

However, it is important to note that not all forms of limestone can serve the purpose. The best types are hard and robust granules that retain their structure.

Excessively soft material can break down and form a solid mass, blocking the filter.

  • Magnesium oxide

Another effective method of removing CO2 from water is using magnesium oxide. The technique can, however, add alkaline salts and hardness to the water.

  • Soda ash sodium carbonate

If your water has high levels of CO2, feed soda ash sodium carbonate into it. The carbonic acid and sodium carbonate react to form sodium bicarbonate.

This method does not add hardness to the water and is very effective when removing carbonic acid from a large volume of water.

Does Reverse Osmosis Water have CO2?

Reverse osmosis water contains carbon dioxide since reverse osmosis does not remove CO2 from the water. The dissolved gas passes through with water molecules during the filtration process.

Also Read: Does Reverse Osmosis Remove Radium?

What Does RO Not Remove?

Reverse osmosis does not remove most organic compounds, chlorine by-products, and dissolved gases like methane, carbon dioxide, and radon.


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Dr. Peter Gleick

Dr. Peter Gleick is an experienced water filtration engineer and technical writer for He is an expert in water purification and filtration, focusing on helping people get clean, safe, and healthy water for domestic use. He has more than 10 years of writing experience and has numerously contributed to leading publications in this field.

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