Does Reverse Osmosis Remove Legionella? (How to Treat)

Reverse osmosis removes Legionella from water. As Legionella bacteria causes Legionnaires’ disease, which is serious pneumonia.

The bacteria are spread through tiny water droplets, and they can infect people who breathe in the contaminated water. RO systems are often used in commercial and industrial settings, such as hospitals and office buildings, to purify water for drinking and cleaning.

Does Reverse Osmosis Remove Legionella?

Yes, reverse osmosis removes legionella. Reverse osmosis forces water by a semipermeable membrane, which eliminates the bacteria and other impurities from the water. As a result, reverse osmosis effectively removes Legionella from water and protects people from Legionnaires’ disease.

What Is Legionella?

Legionella is a genus of Gram-negative bacteria that includes the species L. Pneumophila, which causes legionellosis ( Legionella pneumonia-type disease) and Pontiac fever (a mild flu-like illness).

A silver stain or a culture in buffered charcoal yeast extract agar may be used to reveal Legionella. The bacteria are found everywhere, including in soil and aquatic environments, where at least 50 species and 70 serogroups have been identified.

However, the bacteria in question are not transmissible from person to person; further, most persons exposed to the germs do not become ill. Cooling towers that are not adequately maintained are the source of most incidents. The side chains of the cell wall contain the bases that determine the somatic antigen specificity of these bacteria.(1)

Does Reverse Osmosis Remove Legionella?

History Of Legionella

Legionella was identified following an outbreak among attendees of a 1976 American Legion convention in Philadelphia. Those infected had pneumonia that came to be known as Legionnaires’ disease.

The first cases of Pontiac fever were discovered in 1968 in Pontiac, Michigan, among those who worked at and visited the city’s health department. It wasn’t until after the 1976 Legionnaires’ disease outbreak in Philadelphia that public health experts proved that legionellosis and pneumonia are linked.

The number of reports to the CDC has been steadily increasing since 2000. In the United States, almost 10,000 cases of Legionnaires’ disease were reported by health departments in 2018. This figure, however, may understate the true number of Legionnaires’ disease cases because it is frequently misdiagnosed.

According to a study, the number of Legionnaires’ disease incidents maybe 1.8 to 2.7 times higher than recorded. The majority of illness occurs during the summer and early fall, but they may happen at any time.

What Causes Legionella In Water?

Legionella is bacteria that can be found naturally in bodies of water, such as rivers and lakes, where they tend to exist at low levels and do not cause illness.

Today far more is known about the elements contributing to Legionella’s development and spread than 40 years ago. There have been several fresh cases of Legionnaires’ disease discovered throughout the country, demonstrating that there is still a lot to learn.

Legionella growth can be triggered by Legionella-contaminated water when water supply systems are inadequately maintained, resulting in an environment that promotes Legionella development.

What Causes Legionella In Water

The following are some of the main factors that can contribute to the development of Legionella in a water distribution system:

Excessive water age

The longer water sits in a system or piping, the more likely the water disinfectant will dissipate, allowing germs to develop.


Biofilms, a sort of slime produced by bacteria, protect Legionella from heat and disinfectants when they form on the interior wall of water supply pipes.

Lukewarm water

Legionella thrives in temperature ranges of 77 to 108 degrees Fahrenheit, maintained with lukewarm water.

Dead legs

A “dead leg” occurs when there is no or little water flow in the pipes.

Insufficient disinfectant

Effective water disinfection methods are required to control Legionella in a water system. For example, water authorities use chlorine to disinfect drinking water by creating long-lasting residual disinfection.

Inadequate corrosion control

Corrosion can occur in pipes within a water system, depending on a variety of water quality factors such as disinfectants, temperature, and pH levels. Inadequate corrosion resistance is the greatest conducive condition for Legionella proliferation in water.

Cross connections

Connections between potable and non-potable water can lead to the entry of Legionella into the potable water supply system.

How To Treat Legionella In Water:

Here are different immediate legionella remedies:

  • In the event of an epidemic, short-term solutions such as heat and flushing are frequently successful. This approach is most effective if healthcare workers oversee it. Infection prevention experts must track the temperature at the tap and the length of time it takes to flush.
  • A mechanical chlorinator introducing chlorine-containing compounds to the water is hyper chlorination. It also raises chlorine levels for one to two hours in the water system, long enough to destroy germs. This approach is effective in the treatment of acute or sudden infections. Because chlorine concentrations must be constantly monitored, Legionella quickly re-enters the water distribution system if chlorine levels fall below disinfection standards.

For long-term remediation, some modalities have been employed, which include:

  • In a copper-silver ionization system, a flow-cell chamber with sacrificial copper and silver electrodes is linked to the water supply. The electrodes are linked up, and a direct current is sent between them, allowing ions to be released in a controlled way. Negative ions adhere to negatively charged sites on microorganism cell walls, forming electrostatic connections. These bonds might stress the cell wall, resulting in inefficient nutrient absorption. To summarize, the combination of heat and acid causes protein denaturation, leading to cell death and destruction. According to a comprehensive 2011 analysis of all current treatments, copper-silver ionization appears to be the most effective technology for controlling legionella infection in hospital water systems.
  • Chlorine dioxide is a simple-to-produce manufactured gas that, according to studies from Europe and a famous American university hospital, takes more than a year to be effective against Legionella. It dissolves into chlorite and chlorate, both of which are water-restricted compounds. Chlorine dioxide requires on-site production and is therefore costly to produce. The costs of training, sampling, and testing in a lab are exorbitant.
  • Chlorine-free Monochloramine, a chemical produced by adding chlorine to a solution containing ammonia, is regarded as successful in combating Legionella in biofilms of model plumbing systems. Two different case-control studies of Legionella have suggested that hospitals in areas with domestic drinking water treated with Monochloramine were less likely to report Legionnaires’ disease cases. Free chlorine and Monochromeamine were found in a 2002 CDC study to be comparable disinfectants in a model plumbing system with biofilm-containing legionellosis and other germs.


Reverse osmosis can be an effective method for removing Legionella from water systems, but it is not the only measure that should be taken to protect against the bacteria. It is important to have a comprehensive water management plan that includes regular testing and maintenance of all water systems.


This is my blog about the ways and solutions that can help you improve your health by taking more value from drinking water. As improving health means a lot to me, I decided to create the Water On Top project with the purpose to reveal the benefits of water, the finest products to take our daily water to another level, and much more great stuff about water that I believe is on top of our nutrition.

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