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Does Reverse Osmosis Remove Coliform Bacteria?

Does Reverse Osmosis Remove Coliform Bacteria


Coliform bacteria are not necessarily harmful themselves, but they can be found with harmful bacteria, viruses, and parasites. The simple coliforms might be acceptable to a level in certain cases, but e-coil presence should be zero in any case. 

No matter what the reasons behind removing bacteria from water are, if you’re looking for reverse osmosis efficacy, then, yes, its small micron membrane can trap the various bacteria, including coliform, up to 99% effectively.  

However, how to ensure it’s the best removal method for you? In this blog, I’ll be sharing everything you need to know about it.

Will Reverse Osmosis Remove Coliform Bacteria

Before discussing the removal of coliform bacteria, I would like to discuss shortly what they are actually harmful to us. 

Coliform bacteria, the indicators of water quality, their presence is a sign of fecal contamination with other pathogens. They are found in the environment, particularly in the intestines and waste of warm-blooded animals, including humans. So, if your water has tested positive for coliform and E. coli, it alarms the high risk of waterborne. 

Total coliform bacteria can present with multiple pathogens, such as E. coli strains, salmonella, shigella, campylobacter, vibrio, and norovirus, which can cause diseases such as diarrhea, abdominal cramps, vomiting, and other various infections.

Fecal Coliforms + Escherichia coli (E. coli) = Total Coliforms

Reverse osmosis (RO) is an effective treatment system that can remove a variety of microorganisms such as e-coli, salmonella, shigella, campylobacter, vibrio, norovirus, and amoeba as a part of total coliform from your drinking water. 

Reverse osmosis has an RO membrane, which is important as the heart of the human body. Although it is very small, typically ranging from 0.0001 to 5 microns (micrometers), but can filter out small to large impurities, ensuring safe water. In contrast, bacteria, specifically coliform, range from 1.0-2.0 micrometers long, which are significantly larger than the pores in RO membranes. 

When water is allowed to pass through an RO system, it is passed from multiple stages, which include pre-filters such as sediment and ion exchange, and then to the post-filters like activated carbon media. During this multi-filtration, all the impurities, including total coliform, are filtered out up to 99.999%, resulting in clean and safe water. 

However, all RO membranes are not made equal, and some may have slightly different specifications. If bacteria are your main concern, consider choosing a small RO membrane. 

Reverse Osmosis With UV Light: Our Recommendation

It is important to note reverse osmosis will only trap the bacteria instead of killing them, which is a point important to consider while looking for a reverse osmosis water filter system. Therefore, in the case of water filtration systems, we will suggest using reverse osmosis systems with UV lights. 

Basically, UV in a reverse osmosis system works as disinfection. It kills and inactivates microorganisms, including bacteria, viruses, and parasites, by disrupting their DNA or RNA structure. The integration of reverse osmosis with UV light technology provides an extra layer of protection against harmful bacteria such as coliform and viruses, making it an ideal choice for top-notch water quality. 

Usually,  UV lights are installed before the water enters the RO membrane.  As the water flows through the UV chamber, the microorganisms absorb the UV energy, which damages their DNA or RNA. Thus, the process makes it impossible to grow or cause infections. 

After passing the UV filter, the water is allowed to pass from an RO membrane, ensuring your water is not only purified but also microbiologically safe.

Pros of Reverse Osmosis with UV

  • Water free from chemicals and microbiological.
  • Multi-stage filtration
  • Chemical-Free disinfection
  • Minimal Maintenance

Cons of Reverse Osmosis with UV

  • Expensive 
  • Wastewater is Produced 
  • Consume electricity, which adds to operational costs.

Alternates: Simple Ways to Remove Coliform From Water

Most Americans rely on bottled water, but you can’t spend your life investing in them. If your water has coliform bacteria, there are various methods to get rid of it, including reverse osmosis. 

It may be possible you’re an owner of a private well or getting water from a public water supply, both are at higher risk of coliform. First, wherever possible, you should get rid of the source of the contamination before thinking about ways to remove bacteria from the water.  

You should be aware of how coliforms enter your groundwater and what are the possible ways to avoid them. 

Various simple ways that you can do at home for coliform removal are as follows. 

1. Boiling Your Water For 15 Minutes

Boiling Your Water

Boiling water is the most traditional and effective way to kill bacteria such as coliform and various pathogens, ensuring safe water to drink. This method is simple and can be used in emergencies when other treatment options are not available.

You need to boil the water for 10-15 minutes until the water temperature rises and produces steam. The heat energy can disrupt and denature the proteins and enzymes within the coliform bacteria cells and make them non-functional.

Remember, boiling is effective for coliform bacteria and many other microorganisms but does not remove any physical particles or chemical contaminants that may be present in the water. 

2. Disinfect Your Water By Chlorination

Chlorination is commonly used in municipal water treatment. Adding chlorine, usually in the form of household bleach (sodium hypochlorite), to water can disinfect it and kill coliform bacteria. 

You need to add a high concentration of chlorine in the water to prevent bacterial and pathogenic contamination. When chlorine is added to water, it forms ions that can penetrate the cell membrane and damage the coliform bacteria.

Importantly, the chlorination depends on the concentration of chlorine added, the duration of the chlorine contact with the bacteria in water, pH, and the presence of other water impurities. It may not remove all the cellular debris of bacteria from the water. Therefore, we suggest using additional filtration to improve the water quality. 

3. Use Distillation

water distillers

Distillation is another effective method for killing coliform bacteria, other microorganisms, and various other impurities. It begins with the boiling of water, where it produces steam and changes into a clean liquid, distilled water. 

As the water boils, the heat causes the breakdown of the genetic material (DNA or RNA) of coliform bacteria present in the water. 

During the process, the steam produced from the boiling water is separated from the contaminants, including the inactivated coliform bacteria, which are left behind. Plus, The steam is condensed, converted into liquid, and can be collected in a separate container. 

Water distiller units can be installed at the point of use or floor unit like water dispensers. Being an efficient and effective water distiller might be an ideal choice for various people. However, it requires a significant amount of energy and a slow process as compared to some other water treatment methods.


Reverse osmosis is highly effective method that can remove a wide range of contaminants, including bacteria, viruses, and other microorganisms. In general, RO systems has microscopic pores that are too small to allow bacteria to pass, making them capable of removing coliform bacteria from water. 

In summary, RO is a powerful water purification technology but some additional disinfection methods, such as chlorination or ultraviolet (UV) treatment, can assit to ensure complete and reliable water purification, especially in situations where water quality is a primary concern. 

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