Does Reverse Osmosis Remove Pathogens from Water? Find Out Here!

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The main reason behind the popularity of reverse osmosis water systems is the thoroughness of their filtration process.

Reverse osmosis is hands down one of the best methods for removing various types of contaminants from water.

This also includes contaminants with potentially harmful health effects. But does RO also remove pathogens? Let’s find out!

Key Takeaways

  • Reverse osmosis is great at removing pathogens from water.
  • All pathogen types are addressed with a high level of effectiveness.

Does Reverse Osmosis Remove Pathogens from Water?

So, does reverse osmosis remove pathogens from water? Yes, reverse osmosis does remove pathogens from water. The small size (0.0001 micron) of the pores of the reverse osmosis membrane makes it perfect for removing any types of pathogens.

What is a pathogen in the first place, though? Simply put, this is any type of organism which could introduce a disease to a human being or another living being. This includes some types of protozoa, as well as bacteria and viruses.

Of course, it’s important to consider those separately when thinking about the purification qualities of a water filtration method…

Does Reverse Osmosis Remove Bacteria?

Yes, reverse osmosis systems are very effective at removing bacteria. Very few bacteria can make it through the membrane of a reverse osmosis filter. Even then, the small concentration that makes it to the other side means that they are effectively rendered harmless.

bacteria in water

Does Reverse Osmosis Remove Viruses?

The same goes for viruses. Reverse osmosis is very good at removing various types of viruses like enteric, hepatitis A, norovirus, and others. In fact, it’s probably one of the best approaches for removing viruses available on the consumer market right now.

Does Reverse Osmosis Remove Protozoa (Cysts)?

Finally, when it comes to protozoa, reverse osmosis is also fantastic. It has a very high effectiveness in removing them. You might need to verify that the specific types of protozoa you’re dealing with will be addressed by your RO system, but that should be the case in pretty much all scenarios.

Does Reverse Osmosis Kill Pathogens?

As great as reverse osmosis water purification is, there are also some misconceptions about it. For example, some people falsely believe that it actually kills pathogens. That’s not the case. In reality, they just get rejected. This means that they can’t pass through the RO membrane and they get mixed with the reject water stream.

If you’d want to actually kill pathogens in your water, you’d have to use additional purification methods like UV light.

What Happens When Pathogenic Water Meets an RO Membrane?

When pathogenic water meets a reverse osmosis membrane, only water molecules are able to pass through due to the small size of the membrane’s pores. Almost all contaminants, including pathogens, get rejected. They are mixed with the reject water and sent away.

However, some amount of contaminants can still build up on the membrane over time – remember: RO doesn’t kill them. If the membrane is not cleaned or replaced frequently enough, it may eventually clog or deteriorate. This could lead to pathogens making their way into the filtered water supply eventually.

For this reason, many reverse osmosis system manufacturers will recommend against using their systems for heavily biologically-contaminated water.

Types of Waterborne Pathogens

As we mentioned above, waterborne pathogens can be divided into three main categories. These are bacteria, viruses, and protozoa. All of those are linked to various diseases and health conditions. Some common examples of waterborne pathogens and diseases include:

  • Cholera
  • Typhoid fever
  • coli
  • Hepatitis A
  • Salmonella

Depending on where you live, you might have a higher concentration of some of those. It’s important to get your water professionally tested before investing in a solution like a reverse osmosis system. This will let you know exactly what kinds of pathogens you’re dealing with. And it can help you identify a potentially better solution for filtering your water.

Health Effects

The health effects associated with waterborne diseases can vary. They can range from short-term illnesses to long-term conditions with additional complications. Abdominal and gastrointestinal issues are among the most commonly reported symptoms among people dealing with waterborne pathogens. Other common health effects include:

  • Cramps
  • Diarrhea
  • Constipation
  • Fatigue
  • Excessive sweating
  • Pain in muscles and joints
  • Vomiting
  • Weight loss
  • Dehydration

Even though those symptoms are common for most waterborne diseases, the exact symptoms can vary from one incident to another. If you have noticed any similar symptoms from drinking your home water, you might need to look into a filtration solution.

How Does Reverse Osmosis Work?

Now that we know that reverse osmosis is so great at removing pathogens from water, how does it actually work? Mechanically, it’s pretty simple. Some people assume that this is a complex system involving advanced technology, but the reality is that reverse osmosis is among the simplest types of water filtration available on the market.

The basic idea revolves around a thin semipermeable membrane sheet through which all water diffuses at a high pressure. But only water molecules are able to pass through. Pretty much everything else is too large, gets rejected, and left behind. Those impurities get mixed with the reject water stream and sent away.

As a minor disadvantage to reverse osmosis, the process can result in a lot of wasted water. However, you are often able to reuse that water for other purposes. As long as you’re careful about it and know exactly what you’re dealing with, there is no harm in using reject water for various other applications like household cleaning.

blue reverse osmosis membrane

Other Contaminants Removed by Reverse Osmosis Water Filtration

It’s not just about pathogens. Reverse osmosis is great at removing various other types of contaminants from water, too. This includes, but is not limited to:

  • Aluminum and ammonium (98%)
  • Copper, mercury, nickel, sulfate, sulfite, zinc (97%)
  • Arsenic, barium, cadmium, iron, lead, manganese, magnesium (96%)
  • Selenium (95%)
  • Potassium, sodium (90%)
  • Radium (80%)
  • Nitrates (68%)

As you can see, the process is pretty thorough when it comes to some of the most common types of water contaminants.

And the above list is for the RO membrane alone. However, reverse osmosis systems for home use come with pre and post-filters. Sediment pre-filters are perfect for removing floating particles. And activated carbon is great for removing organic chemicals among other things.

Bottom line: For the average household reverse osmosis should prove more than sufficient.

Limitations: What Is Not Removed by RO?

Even though reverse osmosis is very effective, it’s not perfect. There are some types of contaminants that don’t get effectively removed by the process. This includes certain types of pesticides, such as atrazine. Some organic compounds like benzene also don’t get stripped away. Finally, you might not have a very high success rate with dissolved gases like carbon dioxide, chlorine, and others.

Don’t worry though. That’s what the additional filter stages in an RO system are for. Activated carbon is great for removing pesticides, chlorine, benzene, etc.

If you have any thoughts about the question, does reverse osmosis remove pathogens, please don’t hesitate to leave a comment below!

About the Author Gene Fitzgerald

Gene Fitzgerald is one of the founders of BOS and currently head of content creation. She has 8+ years of experience as a water treatment specialist under her belt making her our senior scientist. Outside of BOS, Gene loves reading books on philosophy & social issues, making music, and hiking.
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