Biofilm and Legionella FAQ
What are Biofilms?
Biofilms can be thought of as bacterial slime layers but in reality, they are biological systems in which the bacteria organize themselves into a coordinated functional community.
Why Are Biofilms Important When It Comes to Legionella?
Biofilms not only have the potential to harbor Legionella, but also provide a fertile breeding ground for it and other harmful bacteria. Over 90% of Legionella in plumbing systems are found in biofilm. There is no good approach to fighting Legionella that doesn’t involve targeting biofilm. Two scientific papers describe the relationship of biofilms and Legionella as:
Consider this: To grow Legionella as a pure culture under lab conditions, you must provide strict environmental conditions and carefully provide several different nutrients. But it is relatively easy to grow Legionella in a biofilm because it has the proper conditions and a supply of nutrients from the microbes found in the biofilms.
With Regard to Legionella, Where Are Typical Biofilms Found?
In the context of Legionella, the cause of Legionnaires’ Disease, a biofilm is often encountered as a collection of cells that have adhered to the inside of a pipe or other equipment that touches water. This can include water softeners, fountains, pumps, water heaters, and most devices that are connected to a building’s plumbing system.
What Are Important Factors in the Development of Biofilms that Can Harbor Legionella?
There are four key factors that can foster the development of Legionella in biofilms:
- Stagnant water
- Warm water temperature
- Low disinfectant levels
- Smoothness of internal piping surfaces
That is not to say that biofilm cannot form in the absence of these conditions. But these conditions tend to encourage even greater biofilm growth when present.
Do All Biofilms Contain Legionella?
No, it is possible to have biofilm that does not contain Legionella. However, most Legionella outbreaks have been correlated with the presence of biofilms. And biofilms can provide a good breeding ground for Legionella if it is introduced to the system. Notably, Legionella is a naturally-occurring bacteria found in ground water and streams, so the chances of it being introduced to any water system can be significant.
Is Heat Treatment a Good Option for Eliminating Legionella in Biofilms?
Unfortunately, Legionella in biofilm is often protected from Legionella remediation measures such as heat treatments since biofilm doesn’t conduct heat well. Moreover, very high levels of heat can cause harm to the elements in a plumbing system making biofilm grown accelerate due to rough piping surfaces. Therefore, heat treatment is not a preferred solution for Legionella in biofilms and in the long-term can make controlling biofilm and Legionella harder.
Can Legionella in Biofilms Be Eradicated with a Hyperchlorination or Superchlorination?
Legionella in biofilm is protected from Legionella remediation measures such as hyperchlorination or superchlorination due to the characteristics of the biofilm. Notably, chlorine doesn’t penetrate biofilm well. And usage of high chlorine levels on a sustained basis often deteriorates the plumbing system making a more area for biofilm to grow in the future. For this reason and another mentioned below, hyperchlorination or superchlorination is not a preferred solution for Legionella in biofilms.
Can Hyperchlorination or Superchlorination of Biofilms Increase the Amount of Legionella in Present in the Plumbing System?
Yes, studies have shown that biofilms exposed to high chlorine levels later demonstrated a significant elevation in bacterial concentrations at the end of cleaning cycle compared the initial level. Said another way, the presence of a high-chlorine concentration does not treat biofilm formation and actually supports an increased amount of bacterial growth during the regrowth period. In addition, in the long-term, the environmental conditions in plumbing systems imposed by a higher chlorine residual encourages the development of a highly resilient biofilm. These high levels of chlorine also deteriorate the piping making plumbing systems more susceptible to biofilm growth.
What is the Best Way to Treat Legionella that is Present in Biofilm?
There are several short-term and long-term treatment options for Legionella remediation that are highly effective in controlling Legionella and providing excellent water characteristics. However, there is no one-size-fits-all solution, as each solution has different safety and financial considerations.
That is why is it important to work with a truly independent Legionella consultant such as Nancrede Engineering. Nancrede Engineering will find the most cost-effective Legionella control solution based on your facility’s unique characteristics. Contact Nancrede Engineering to learn more.