Understanding Biofilm
In water systems, tanks, and pipelines, it is estimated that up to 80% of bacteria exist in biofilm form, colonising interior surfaces rather than living as free-floating planktonic cells.
A biofilm is a structured community of microorganisms attached to a surface and enclosed in a self-produced matrix of extracellular polymeric substances (EPS). This matrix — a combination of polysaccharides, proteins, lipids and DNA — gives biofilms their characteristic slimy texture and provides bacteria with extraordinary protection.
How Biofilm Forms
Calcium scaling and biofilm are mutually reinforcing phenomena in water systems.
Biofilm development follows a reproducible sequence:
- Initial attachment — planktonic bacteria make contact with a surface
- Reversible adhesion — bacteria adhere loosely; removal is still possible at this stage
- Irreversible adhesion — the EPS matrix begins to form, anchoring cells permanently
- Maturation — a three-dimensional community develops with distinct architecture
- Dispersal — cells are released to colonise new surfaces, completing the cycle
Even electropolished stainless steel surfaces are vulnerable. Even desalinated, demineralised and Ultra Pure Water (UPW) can support biofilm growth, because oligotrophic bacteria (organisms adapted to extremely low nutrient levels) will colonise any available surface.
Conditions That Accelerate Growth
- Temperature between 20°C and 45°C (optimal range for most pathogens)
- Stagnant or low-flow water
- Nutrients: carbon, nitrogen, phosphorus, trace minerals
- Any wetted surface — natural or man-made
- Dead-end pipes and infrequently used branch lines
Why Biofilm Is Difficult to Remove
The EPS matrix is the primary reason biofilm survives conventional treatment:
- It reduces penetration of biocides by up to 1,000-fold compared to planktonic bacteria
- It provides structural protection against temperature extremes, pH changes and mechanical shear
- It enables intercellular communication (quorum sensing), allowing coordinated resistance responses
- It acts as a nutrient reservoir, supporting survival during periods of starvation
Industrial and Economic Impact
The consequences of uncontrolled biofilm formation extend across virtually every industry that uses water:
| Sector | Primary Impact | Examples |
|---|---|---|
| Maritime | Reduced heat transfer, corrosion, hull fouling | Box coolers, ballast water, sanitary systems |
| Food & Beverage | Product contamination, reduced shelf life, batch loss | Breweries, dairy, meat processing |
| Water Treatment | Membrane fouling, UV reactor blockage, tank contamination | RO systems, UF membranes, storage tanks |
| Energy | Reduced cooling efficiency, increased fuel costs | Cooling towers, heat exchangers |
| Oil, Pulp & Paper | MIC corrosion, pipeline blockage | Storage tanks, process pipelines |
| Healthcare | Pathogen transmission risk (Legionella, Pseudomonas) | Hospitals, care homes, dental units, public buildings |
| Recreation | Health risk, aesthetic deterioration | Swimming pools, jacuzzis, ornamental fountains |
| Agriculture | Dripper blockages, crop & root diseases | Irrigation systems, greenhouses |