Why Chemical Disinfection Alone May Not Remove Biofilm
An evidence-led guide for understanding biofilm in managed water and hygiene systems.
Killing cells in a biofilm and removing the biofilm are different outcomes. A 2026 food-surface study found that sodium hypochlorite on its own left biofilm structure in place, while hypochlorite combined with microbubbles removed it, illustrating why physical action matters.
The 2026 Journal of Applied Microbiology study
A study published in the Journal of Applied Microbiology on 21 January 2026 (Hou et al., doi 10.1093/jambio/lxag023) grew Salmonella Typhimurium and Staphylococcus aureus biofilms on stainless steel and PVC coupons, two materials common in food-processing plant, and treated them with water, 50 mg/L sodium hypochlorite, 50 mg/L chlorine dioxide, or each sanitiser combined with microbubbles.
The combinations outperformed the sanitisers alone by an additional five to six log reductions. After ten minutes, the hypochlorite–microbubble combination reduced Salmonella on stainless steel to below the detection limit; the chlorine dioxide–microbubble combination reduced it to about 2.6 log CFU per coupon. Residual populations were consistently higher on PVC than on stainless steel, and Salmonella was harder to remove than S. aureus on both materials. Scanning electron microscopy showed no biofilm remaining on coupons treated with the hypochlorite–microbubble combination, whereas biofilm remained on coupons treated with hypochlorite alone or water alone. Staining for extracellular material confirmed that the microbubble combination removed the most matrix.
Kill, reduction and removal are different endpoints
The result that matters most for practice is the microscopy: chemical treatment alone could reduce viable counts while leaving the structure of the biofilm on the surface. Surviving matrix and embedded cells provide a foothold for regrowth and can shield organisms from the next treatment. This is why laboratory endpoints such as inhibition, log reduction and eradication should not be read as interchangeable.
Microbubbles add physical action: shear at the surface and disruption of the matrix, which improves access for the oxidant. The general lesson is not specific to microbubbles. Mechanical cleaning, flow, flushing and surface condition all contribute to whether a biofilm is removed rather than merely damaged, which is why hygiene programmes separate cleaning from disinfection.
What this study does and does not establish
It establishes that, for two food-borne organisms on two materials in the laboratory, adding microbubbles to a 50 mg/L sanitiser produced substantially greater inactivation and visibly more complete biofilm removal than the sanitiser alone, and that surface material affected the outcome. It supports the principle that disinfection chemistry is one component of biofilm control alongside physical removal.
It does not establish that chlorine dioxide is ineffective against biofilm, nor that microbubbles are required. The biofilms were young, single-species laboratory cultures; the sanitiser concentrations and contact times were fixed by the experimental design; and the most complete removal in this study was reported for the hypochlorite–microbubble combination, not for chlorine dioxide. The chlorine dioxide was a laboratory solution; ChloroKlean products were not tested. Findings on food-contact surfaces do not transfer to pipework, cooling systems or spa plumbing without separate evidence.
Evidence and uncertainty
Published biofilm studies are valuable for understanding mechanisms, but their conditions may not match a particular installation. Species, surfaces, deposits and operating conditions should be recorded when interpreting evidence.
For safety-critical systems, decisions should be documented through the relevant risk assessment and management plan.
Choosing the next question
A useful next step is to identify what is known, what is inferred and what needs verification. This avoids treating a general reference as a site diagnosis.
Where a product is considered, confirm the intended use, authorisation and label directions independently of this educational guide.
A proportionate biofilm-management approach
Use this sequence to frame investigation and control; it is not a dosing protocol.
Define the system and risk
Map wetted surfaces, operating conditions, users and relevant legal or sector guidance.
Gather evidence
Review inspection, operational, residual and microbiological records rather than relying on one indicator.
Address contributing conditions
Consider cleaning, hydraulics, nutrients, stagnation and equipment condition alongside any authorised biocide programme.
Verify and review
Document the intervention and review results through the site’s written scheme or hygiene plan.
Expert Insights
"Biofilm control is a system-management question: chemistry, surfaces, flow, cleaning and verification all matter."
ChloroKlean Technical Team
Technical review team
About the Reviewer
Gavin Owen
Managing Director, ChloroKlean
Gavin Owen leads ChloroKlean's technical and commercial operations, bringing over 20 years of experience in industrial chemical distribution and water treatment. He oversees product development, regulatory compliance strategy, and the company's BPR compliance programme across PT2, PT4, PT5, and PT11 product types. Gavin works directly with water treatment professionals, facilities managers, and public health engineers across healthcare, leisure, food processing, and industrial sectors.
Frequently Asked Questions
Common questions about this topic, answered by our technical team.
Scope and safe-use note
- This is general educational information, not a dosing instruction or a product label.
- Use only a biocidal product authorised for its intended product type and follow its label, Safety Data Sheet and site risk assessment.
- Investigate system design, cleaning, monitoring and microbiological findings with a competent person where there is a health risk.
Published evidence about a disinfectant or another product does not establish efficacy, authorisation or an appropriate use pattern for any ChloroKlean product.
Related Resources
Continue exploring our knowledge base and product information.
Biofilm learning hub
Browse the connected biofilm guides.
What is EPS in biofilm?
The matrix that chemical treatment must get through.
Chlorine dioxide and biofilm: the evidence
How to read chlorine dioxide biofilm studies.
Food-safe disinfectant guide
Food-contact disinfection in the UK framework.
PT4 food and feed hygiene
Product-type information for food-contact surfaces.
Sources & References
This article references guidance from the following authoritative sources:
- Biofilms: survival mechanisms of clinically relevant microorganisms
Industry Standard - Frontiers in Microbiology (PMC)
- Legionella and the prevention of legionellosis
WHO - World Health Organization
- ACOP L8: Legionnaires' disease
HSE - Health and Safety Executive
- Biocidal Products Regulation
ECHA - European Chemicals Agency
- Application of combining microbubbles with sanitizers to inactivate biofilm on stainless steel and polyvinyl chloride (21 January 2026)
Industry Standard - Journal of Applied Microbiology
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