Biofilm is one of the more persistent problems found in water distribution systems, process pipework, storage tanks and recirculation loops.
It develops when microorganisms attach to wetted surfaces and build a matrix that helps the microbial community remain attached. Once established, biofilm can contribute to recurring microbiological contamination, poor water quality, reduced hygiene performance and repeated cleaning requirements.
Removing biofilm is therefore rarely as simple as adding more disinfectant. The right strategy depends on the type of system, water quality, hydraulic conditions, pipe material, available cleaning methods and whether the objective is to remove an existing problem or prevent it from returning.
Established biofilm is normally controlled using a combination of physical cleaning or flushing, microbial disinfection and correction of the operating conditions that allowed the biofilm to form. Ozone can form part of this strategy where ozonated water can be circulated through the affected system at a controlled dissolved ozone concentration and contact time.
What Causes Biofilm in Water Pipes?
Biofilm begins when microorganisms attach to a surface in contact with water. Over time, attached organisms produce extracellular material that creates a structured layer on the pipe or equipment surface.
Several conditions can encourage biofilm development:
- Stagnant or low-flow sections
- Dead legs and unused branches
- Long water residence time
- Nutrients or biodegradable organic matter in the water
- Suitable water temperatures
- Rough, corroded or fouled surfaces
- Inadequate cleaning or flushing
- Loss of disinfectant control where a residual is required
- Repeated contamination from upstream equipment or storage
A recurring biofilm problem should therefore be treated as a system problem, not simply a disinfection problem.
Why Is Established Biofilm Difficult to Remove?
Free-floating microorganisms in water are generally easier to expose to a disinfectant than microorganisms embedded within an established surface biofilm.
The biofilm matrix can consume or reduce penetration of an oxidant before the full treatment reaches deeper layers. Mature biofilm can also contain organisms in different physiological states, meaning that treatment response is not necessarily uniform throughout the layer.
This is one reason why a system may temporarily produce acceptable microbiological results immediately after disinfection and then become contaminated again.
Killing microorganisms and physically removing deposited biofilm are not always the same thing.
A successful remediation strategy may need oxidation or disinfection to weaken the biofilm, followed by hydraulic or physical removal of loosened material.
How Can Biofilm Be Removed from Water Pipes?
There is no single treatment method that is best for every system. The appropriate approach depends on system access, water chemistry, materials, temperature, contamination level and whether the objective is remediation or ongoing control.
| Treatment method | Main strength | Typical limitation |
|---|---|---|
| Mechanical cleaning / flushing | Physically removes biomass, sediment and deposits from the system. | Access may be difficult in complex, small-bore or fixed pipe networks. |
| Heat sanitisation | Strong sanitation method in systems designed for thermal treatment. | Energy demand, material limitations and temperature distribution. |
| Chlorine / chlorine dioxide | Established microbial-control technologies; residual protection may be possible. | Performance depends on chemistry, demand, concentration and contact time. |
| PAA / hydrogen peroxide | Widely used oxidation and sanitation options in selected industrial systems. | Chemical handling, residual management and process compatibility. |
| Ozone | Strong on-site oxidation and well suited to controlled recirculation loops. | No persistent residual; ozone demand, contact time and material compatibility are critical. |
Mechanical Cleaning and Flushing
Where pipe access and system design allow it, physical cleaning can remove material directly from internal surfaces.
Methods may include:
- High-velocity flushing
- Pigging or swabbing
- Tank cleaning
- Drain-and-flush procedures
- Removal and cleaning of individual components
Physical cleaning has an important advantage: detached biomass and sediment are actually removed from the system rather than simply disinfected in place.
Heat Treatment
Hot-water sanitisation can be highly effective in systems specifically designed for thermal treatment.
Its limitations can include energy consumption, heat-up and cool-down time, material restrictions and difficulty achieving the required temperature throughout a large or complex pipe network.
Chemical Disinfectants
Chlorine, chlorine dioxide, peracetic acid, hydrogen peroxide and other chemical disinfectants are widely used for microbial and biofilm control.
Their effectiveness depends on concentration, contact time, water chemistry, disinfectant demand and access to the contaminated surface.
The appropriate chemical strategy should therefore be assessed against the actual system rather than assuming one disinfectant will always outperform another.
Ozone Treatment
Ozone is a strong oxidant that can be generated on site and dissolved into a water stream for recirculation through pipework, tanks and process equipment.
When ozone contacts microorganisms and organic material within a biofilm, oxidation can affect both microbial viability and components of the biofilm matrix.
Its suitability depends on achieving sufficient dissolved ozone concentration and contact time at the location where treatment is required.
Where Does Ozone Fit in Biofilm Control?
Ozone is particularly useful where treated water can be circulated through contaminated pipework and the process can be monitored and controlled.
Typical applications may include:
- Process-water loops
- Food and beverage pipework
- Clean-in-place systems
- Storage tanks and transfer lines
- Industrial recirculation loops
- Irrigation and agricultural water systems
- Selected cooling-water duties
- Equipment sanitation loops
Ozone is generated when required rather than stored as a bulk sanitising chemical. After treatment, it decomposes rather than providing a long-lasting persistent residual.
That can be either an advantage or a limitation.
For a controlled recirculation or CIP loop, a non-persistent residual may be desirable. For a long distribution network where lasting protection throughout the system is required, another residual-disinfectant strategy may be more appropriate.
Our CIP application page covers the use of ozonated water for pipework, tanks, process loops and equipment sanitation.
Can Ozone Remove Established Biofilm?
Ozone can contribute to biofilm oxidation and disruption and can reduce microorganisms exposed to treatment, but an established biofilm problem should not be described as though it will simply disappear after one ozone cycle.
A more realistic remediation programme may combine initial cleaning, controlled ozonated-water circulation, sufficient contact time and flushing of detached material.
The effectiveness of ozone treatment will depend on biofilm maturity, pipe geometry, water temperature, organic load, ozone demand, flow velocity, dissolved ozone concentration, contact time and the ability to flush the system afterwards.
There is therefore no credible universal statement such as “ozone removes biofilm in X hours” that can be applied to every water system.
How Can Biofilm Be Prevented from Returning?
Removing an existing biofilm without correcting the conditions that allowed it to develop can lead to recurrence.
Low-flow and unused sections can create favourable areas for microbial growth. Remove redundant branches where possible or include them in routine flushing.
Storage tanks, oversized pipework and poorly used branches can create long residence times and should be reviewed when contamination keeps returning.
Organic material can support microbial growth and increase oxidant demand. Better upstream water treatment can therefore reduce regrowth conditions.
Routine flushing, periodic sanitation, monitoring and a defined disinfection strategy are more reliable than waiting for visible contamination to return.
How Is an Ozone System Designed for Biofilm Control?
An ozone biofilm-control system should be designed around the complete water circuit rather than selecting an ozone generator from pipe volume alone.
Ozcon's Ozone Water Injection Systems are designed around controlled transfer of ozone into water rather than generator output alone.
For biofilm control, dissolved ozone measurement is normally more useful than assuming the delivered water concentration from generator output. ORP can provide useful process information, but it does not directly measure dissolved ozone concentration.
See: Dissolved Ozone vs ORP .
Materials also need to be checked carefully. Seals, pumps, valves, plastics and elastomers may respond differently to ozone depending on concentration, temperature and exposure duration.
See: Ozone Compatible Materials .
What Information Is Needed to Assess a Biofilm Problem?
Before recommending an ozone treatment approach, it is useful to understand the complete water system and what has already been tried.
System Information
- Total pipework volume
- Pipe diameter and approximate length
- Tank volumes
- Recirculation flow
- Operating pressure
- Materials of construction
- Dead legs or stagnant areas
- Existing pumps and circulation arrangement
Water Information
- Water source
- Temperature
- pH
- Turbidity
- Organic load where known
- Existing disinfectant
- Microbiological results
- Contamination history
Treatment Objective
- One-off remediation
- Periodic sanitation
- Continuous biofilm control
- Process-water hygiene
- CIP sanitation
- Reduction of chemical dependency
- Specific microbiological target
- Current cleaning method
Is Ozone the Right Solution for Every Biofilm Problem?
No.
The objective is not to install an ozone generator. It is to understand why biofilm is forming, remove or control it, and prevent it from returning.
Send us the system volume, flow rate, water quality, materials, existing cleaning method and microbiological information available. We can review whether the problem is better approached through flushing, process changes, ozone treatment or a combined sanitation strategy.