How to Remove and Prevent Biofilm in Water Systems
Maintaining the safety of building water systems, including the prevention of bacteria like legionella is of critical importance. Failure to do so can lead to infections that pose serious health risks to those exposed to such water systems.
One important factor influencing the spread of bacteria within a water system is the presence of biofilms. This article, written by the water safety specialists at Water Treatment Services explores the nature of biofilms, their formation and impact on water pipes, tanks, and other items of plant and equipment that use water. It highlights the risks associated with biofilms and emphasises the significance of prevention and early intervention as a key control strategy. Additionally, the article discusses chemical treatments and routine water management practices necessary to control and eliminate biofilms, to ensure the safety of water systems for all users.
Do biofilms increase legionella risks?
It’s crucial to maintain hot and cold water systems so they are safe for people to use. If this does not happen, those water systems can lead to infections caused by bacteria that have been allowed to colonise the system. Legionella is a classic example of a bacterium that can be controlled and kept at safe levels, yet can cause serious illness if allowed to multiply and spread. Legionella is associated with Legionnaires’ disease, a type of pneumonia that can be fatal in some people.
One area that determines how easy it is for legionella and other bacteria to spread throughout a water system concerns the presence of biofilms. In this article, we’ll look more closely at what these are and how to tackle them.
What are biofilms?
In simple terms a biofilm is a collection or colony of micro-organisms that attaches to something else. In this case, it could be the interior surfaces of a water pipe, inside a water tank, on heat exchange surfaces, or inside a cooling tower. In such circumstances biofilm requires water to develop. The fact that it is out of sight within a water system means that it has the potential to grow and spread throughout the system unseen.
Biofilms are slimy, giving them the power to attach to all manner of surfaces as we’ve noted. While legionella bacteria can exist in natural water sources, its presence in manmade water sources poses greater risk. If biofilms are present, legionella and other bacteria use it as a source of protection and nourishment. The biofilm helps to protect the bacteria from attack, and also helps it to multiply; it can potentially spread through an entire water system with the help of biofilm. This can lead to an outbreak of Legionnaires’ disease among those exposed to the water system.
It’s obvious, then, that preventing and removing these biofilms is a key part of the process of maintaining a water system and ensuring it is safe to use.
Prevention is better than cure
We’ve all heard this before. In this case, early stage prevention of biofilms is far better than removal, although ongoing control within a water system is of paramount importance to maintain clean water conditions and good heat transfer properties.
The first step is to prevent the water conditions that would encourage the formation of biofilm. For example, biofilms need nutrients to establish and grow, so it is vital to ensure the incoming water supply is safe to use and that the water system itself is as clean and safe as possible. Older pipework, for instance, may have increased levels of sediment in it compared to new pipes. Keeping the water system clean and well maintained is key to making sure there are fewer nutrients that would encourage biofilms to form.
They also require water to grow, as we noted earlier. We obviously cannot prevent that from being present in a water system, but we can make sure there is no stagnant water sitting in disused pipes that are connected to the system. Removal of these disused elements that promote stagnation helps to remove the risk. Similarly, infrequently used taps, shower heads, and pipework can lead to a build up of biofilm in those areas. If removal isn’t possible, there should be a plan to flush through the infrequently used parts of the water system regularly to reduce the risks.
Another easy step to take to reduce the chance of adding nutrients to the water is to make sure water storage tanks are properly covered, so that nothing can drop into the water from above. Checks like these can form part of the regular maintenance checks that should take place to keep the legionella risk as low as possible.
Using chemical treatments to remove biofilm
Even if you follow all the above steps and regularly flush through the waters systems, take samples from various outlets, and refresh your legionella risk assessment, you may still need to treat the water to prevent the formation of biofilm to ensure it is safe for use.
Regular disinfection of the water is typically conducted to ensure it is safe for use. Chlorine dioxide (ClO2) is the most common chemical treatment used for this purpose as it is highly effective against biofilm. There is however a limit to how much can be used while still maintaining a safe water supply. There is a balance between usage and what needs to be added to the water to successfully remove the biofilms.
The Health and Safety Executives’ guidance document HSG274 Part 2 dealing with the control of legionella bacteria in hot and cold water systems includes a specific section on the use of biocide treatments. It mentions the importance of keeping hot and cold water at the appropriate temperatures, as this can ensure each water source either kills the legionella bacteria through heat or reduces it to a dormant state.
HSG274 also mentions copper and silver ionisation as a method for controlling biofilms and removing existing ones. It does this by releasing ions into the water and has been shown to work well with managing biofilm formation. Further information on chlorine and silver stabilised hydrogen peroxide is also given in the document which makes a very useful reference point if you’re considering chemical treatments for the control of biofilm.
Focusing on routine water treatment to control biofilm
Any legionella risk assessment should indicate whether regular dosing of the water system to combat and control biofilms is required, along with maintaining legionella and other bacteria at safe levels. While water testing is not always required, it is best to test if you are treating the water. This helps to ensure any chemicals are being dosed at the correct levels. If identified bacterial levels are higher than they should be, adjustments may be required to the chemical dosing levels. It’s an indication that efforts to remove biofilms – and indeed bacteria – are not working as they should be.
Who has responsibility to control legionella in buildings?
Managing the risk of legionella in a building you own or manage is your responsibility. In the UK, the law is clear and says you must do all you can to limit the presence of legionella, and by association, biofilms in the water supply. If you are in any doubt over what you should do, or you do not possess the required expertise and training to be able to conduct your duties effectively, you can employ someone to do this for you. This is often preferable for larger businesses or buildings with complex water supplies.
This ensures that someone with the relevant training and knowledge can assess the treatment required to remove and control biofilms within the water system. They’ll be able to handle regular testing when required, as well, to make sure the chemical treatments are working as they should be.
Expert legionella and water safety solutions
Water Treatment Services offer a range of specialist legionella and water management solutions to support those responsible for the safety of water systems including business owners, landlords, the statutory duty holder and responsible person.
Contact us today to learn how our water safety specialists can help you manage your water systems, maintain regulatory compliance and so keep people safe.
With offices in London serving the South and South East England, Manchester (North West), Birmingham (Midlands), Bristol (South East England and Wales), Leeds (North and North East) and Glasgow (Scotland), supported by regional teams of specially trained technicians and engineers we can offer specialist Authorising Engineer support, legionella risk assessments, training, water quality analysis and other risk management solutions throughout the UK and Internationally.
Contact us today to learn how our water safety and legionella management solutions can help you.
