What is biofilm and why is it a problem in water systems?

Biofilm consists of microorganisms that attach to a surface and build a protective structure around themselves.

In a water system, biofilm can establish itself on the inside of pipes, tanks, valves and other water-carrying components. It can be very thin and difficult to see, but still affect the microbiological quality of the system.

It is also one of the reasons why a water sample can sometimes look good after treatment, but problems later recur.

Short answer: what is biofilm?

Biofilm is a community of microorganisms that are attached to a surface and embedded in a protective, slimy structure.

In water systems, it can occur on, among other things:

• Pipe walls
• The inside of water tanks
• Valves and fittings
• Filters
• Nozzles and taps
• Heat exchangers
• Other surfaces that regularly come into contact with water

Biofilm therefore does not need to float visibly in the water. It can be attached to the inside of the system.

How is biofilm formed?

Biofilm develops incrementally.

First, microorganisms attach to a surface. Thereafter, they can begin to multiply and produce substances that together form a protective structure around the microorganisms.

Over time, biofilm can develop into a more complex microbiological community.

Water passing through the system can simultaneously carry nutrients and new microorganisms.

This means that the inside of a water system can become an environment where microorganisms establish themselves even when the water initially looks clean.

Why does biofilm occur in water pipes?

Water systems contain many surfaces where microorganisms can attach.

The risk is affected by, among other things:

• Water quality
• Temperature
• How long water remains stagnant
• Flow rate
• The amount of organic material and other nutrients
• Pipe material and system design
• Areas with low or no circulation

A system where water regularly becomes stagnant can therefore have different microbiological conditions than a system with continuous turnover.

This is one reason why biofilm is relevant in everything from properties and industries to tanks, process systems and other installations involving water.

Can you see biofilm?

Sometimes, but not always.

Heavy biofilm can appear as a slippery, slimy or discolored coating.

But biofilm can also be very thin.

This means that a pipe or a tank does not have to look dirty for microbial growth to be present on the surface.

Therefore, sight, smell or taste alone should not be used as proof that a water system is microbiologically clean.

Is biofilm the same as dirt?

No.

Dirt can consist of particles, sediment, minerals or other material that has accumulated in a system.

Biofilm, on the other hand, is biological.

It consists of microorganisms together with the structure that the microorganisms build around themselves.

In practice, biofilm and other coatings can coexist on the same surface.

This can make the situation even more complex.

Why is biofilm harder to manage than bacteria in water?

Microorganisms that are freely present in the water are directly exposed to the treatment being used.

Microorganisms in a biofilm, on the other hand, are located in a protective structure and are also attached to the system's surfaces.

This can mean that biofilm acts as a reservoir for microorganisms.

Even if the amount of microorganisms in the water volume itself is temporarily reduced, there can still be microorganisms remaining in the system.

Therefore, it is sometimes necessary to consider the entire installation, not just the water that passes through it.

Why can bacteria return after disinfection?

There are several possible reasons.

One of them is biofilm.

If a treatment primarily affects microorganisms in the water phase but does not deal with an established biofilm, microorganisms can later spread from the system's surfaces to the water.

This can lead to a pattern where water samples improve after treatment, but microbiological problems recur after some time.

This does not automatically mean that the disinfection has been ineffective.

The problem may be that the system itself contains an established microbiological load.

Where in a water system does biofilm thrive?

Biofilm can in principle form on all water-affected surfaces, but some parts of a system can be more exposed.

Examples are areas with:

• Low flow
• Stagnant water
• Uneven temperature
• Hard-to-reach pipe sections
• Branches that are rarely used
• Tanks where water remains stagnant
• Filters or other surfaces with a large contact area

It is therefore important to understand how the entire water system is constructed when trying to identify the cause of recurring microbiological problems.

What is the significance of temperature?

Temperature affects how different microorganisms can grow.

Different species have different optimal temperature ranges, meaning there is no single temperature that applies to all biofilm.

But temperature is an important parameter in many water systems.

Installations where water periodically stands still and at the same time reaches temperatures favorable for microbial growth particularly need to be managed with well-functioning routines.

Can biofilm affect water quality?

Yes.

An established biofilm can contribute to microbiological load in the water and make it more difficult to maintain stable water quality.

In some systems, biofilm can also affect:

• Odor
• Taste
• Flow
• Technical function
• Corrosion
• The effect of disinfectants

Which effects occur varies greatly between different systems.

Biofilm and Legionella

Legionella is often discussed in connection with biofilm because the bacteria can occur in technical water systems where the right conditions exist.

Biofilm can create an environment where different microorganisms live together and where certain microorganisms may have better opportunities to survive.

This means that the work of preventing Legionella is not solely about bacteria that are currently freely present in the water sample.

The system's temperature, circulation, design and microbiological status are also important factors.

Can ordinary chlorine remove biofilm?

Chlorine is widely used for microbiological control and disinfection of water.

But an established biofilm can be significantly more resistant than microorganisms that are freely present in the water phase.

Organic material and other substances in the system can also consume disinfectants.

The effectiveness of a treatment therefore depends on, among other things:

• Concentration
• Contact time
• Water quality
• pH
• Temperature
• The extent of the biofilm
• The system's design

It is therefore difficult to assess a biofilm problem solely based on which disinfectant is used.

How does chlorine dioxide work against biofilm?

Chlorine dioxide is used in water treatment for both microbiological control and in systems where biofilm is part of the problem.

Chlorine dioxide acts as an oxidant and has different chemical properties than traditional chlorination.

This can make the technology relevant when needing to work with both microorganisms in the water phase and the microbiological load present on surfaces in the system.

However, even here, the result is affected by dosage, contact time, water quality and the extent of the biofilm.

A heavily established biofilm may require more extensive initial treatment.

Sanitation and continuous treatment are not the same thing

It is important to distinguish between sanitizing a problem and preventing it from returning.

A system with established biofilm may require an initial treatment whose goal is to reduce the existing microbiological load.

Thereafter, continuous water treatment can be used to maintain control.

These are thus two different tasks:

• First, to restore the system
• Then, to keep it stable

This is an important principle in the treatment of many technical water systems.

Can biofilm just be flushed away?

Flushing can help remove loose material and improve water turnover.

But biofilm is attached to the surface.

Therefore, ordinary flushing is not necessarily sufficient to remove established biofilm.

In some systems, mechanical cleaning, flushing and chemical treatment are combined depending on the system's design and the extent of the problem.

How do you know if a system has biofilm?

It is not always possible to determine visually.

Recurring microbiological anomalies despite treatment can be an indication that the problem is established somewhere in the system.

An investigation can include, among other things:

• Water sampling
• Assessment of the system's design
• Temperature measurements
• Checking stagnant lines
• Inspection of tanks and components
• Sampling from surfaces

Which methods are relevant depends on the facility and the type of microbiological problem suspected.

How can biofilm be prevented?

There is no universal method, but some basic principles are important.

A well-designed system should, as far as possible, avoid unnecessary stagnant water and areas with poor circulation.

It is also important to:

• Have good water turnover
• Control temperatures
• Maintain tanks and pipe systems
• Have functioning routines for cleaning and disinfection
• Monitor water quality
• Address microbiological problems before they can establish themselves

In systems with continuous microbiological load, continuous dosing of a suitable disinfectant may also be relevant.

How does Xinix work with biofilm in water systems?

Xinix works with solutions for disinfection and microbiological control within FreeBact®.

For larger and continuous water systems, FreeBact® Dosage is primarily used.

FreeBact® Dosage is developed for continuous dosing in various types of water systems, from properties and industries to pools, spas and hospitals.

In a system where biofilm has already been established, the situation first needs to be assessed based on water quality, system design and the extent of the problem.

Thereafter, the correct treatment strategy can be developed.

Common questions about biofilm

Is biofilm dangerous?

Biofilm is not a single substance or a specific bacterium.

The significance of biofilm depends on which microorganisms it contains and in which system it occurs.

In drinking water and technical water systems, biofilm is relevant because it can contribute to microbial growth and make microbiological control more difficult.

How quickly does biofilm form?

There is no general time limit.

How quickly biofilm develops is affected by, among other things, microorganisms, temperature, water quality, nutrient availability, flow and the material of the surface.

Does biofilm only exist in old pipes?

No.

Biofilm can also form in new systems if the conditions are favorable.

Old installations may have more extensive coatings, but the system's age is not the only decisive factor.

Can biofilm be present in a water tank?

Yes.

The inside of tanks is a typical water-affected surface where microorganisms can establish themselves.

The risk can increase when water remains stagnant for longer periods.

Can biofilm be present even if the water looks completely clear?

Yes.

The appearance of water says very little about the microbiological status on the inside of a piping system.

Clear water can pass through a system where biofilm is present on the surfaces.

Does biofilm disappear if you change the water?

Not necessarily.

Draining and refilling a system changes the water volume, but biofilm attached to the tank or pipe surfaces can remain.

Summary

Biofilm is a microbiological layer that can establish itself on surfaces in contact with water.

In a water system, it can be found in pipes, tanks, valves and other components, among other places.

The problem is that the microorganisms are attached to the surface and protected by the biofilm's structure.

This can make them harder to access than microorganisms that are freely present in the water.

Therefore, treatment of recurring microbiological problems often needs to encompass the entire water system, not just the water volume itself.

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Thank you for reading all the way here!
For questions & concerns, please don't hesitate to contact us.

Alexandra Németh, Marketing Manager, Xinix Global AB
alexandra@xinix.se
Mobile: +46 70-78 601 678