Chlorine Dioxide and Reverse-Osmosis Membrane Compatibility
An evidence-led guide for understanding biofilm in managed water and hygiene systems.
Chlorine dioxide is used upstream of reverse-osmosis systems for biofouling control, but 2026 laboratory studies show that polyamide membranes are not immune to it: concentration, pH and exposure time all govern whether the selective layer is damaged.
The 2026 RSC Advances study
A study first published in RSC Advances on 21 July 2026 (Arliyani et al., Institut Teknologi Sepuluh Nopember, doi 10.1039/d5ra09010e) exposed thin-film composite polyamide reverse-osmosis membrane coupons to chlorine dioxide at different concentrations and pH values, then assessed them by permeate flux, scanning electron microscopy with elemental analysis, and contact-angle measurement.
Higher chlorine dioxide concentration and alkaline pH accelerated degradation: permeate flux rose (a sign of a compromised selective layer), surfaces deformed and cracked, elemental composition shifted and wettability changed. The mildest condition tested, 0.5 ppm chlorine dioxide at pH 6, produced the least structural change and stayed closest to the untreated membrane. The authors describe this as the most favourable balance between preserving the membrane and retaining the disinfectant's operational advantages. Importantly, they note that biofouling itself was not measured; no microbial adhesion or biofilm-growth experiments were run.
Related 2026 membrane evidence
A separate study in the Journal of Environmental Chemical Engineering (Wang et al., April 2026, doi 10.1016/j.jece.2026.122119) treated a fully aromatic polyamide membrane (NF90) with chlorine dioxide for 96 hours at neutral pH. It reported increased pore size and surface roughness, greater hydrophilicity and water permeability up to 63% higher, with solute passage rising more steeply. Unlike chlorination, no halogen incorporation into the polymer was detected even at 250 mg/L as Cl₂; the proposed mechanism was hydrolytic breakage of amide bonds. The authors characterise polyamide degradation by chlorine dioxide as slower than by chlorine, but real.
Read together, the two studies agree on direction: chlorine dioxide attacks polyamide more slowly than free chlorine and by a different route, but it does attack it, and the rate rises with concentration, exposure time and (in the RSC study) pH. Statements that chlorine dioxide 'does not react' with polyamide are not supported by this evidence.
What these studies do and do not establish
They establish that polyamide membrane damage from chlorine dioxide is a function of dose, pH and time, and that low concentrations near neutral-to-slightly-acidic pH caused the least change in laboratory exposure. They give operators a reason to treat membrane compatibility as a parameter to be specified and monitored, not assumed.
They do not establish a safe operating envelope for any real plant. Both were bench studies on coupons with the oxidant in continuous contact; neither ran a pressurised element, a full pre-treatment train, or a biofouling challenge, and neither reported long-term rejection data under operating conditions. Membrane manufacturers' warranty limits remain the governing constraint. ChloroKlean products were not tested, and this guide makes no claim about their compatibility with any membrane; confirm with the membrane supplier and the product's technical documentation before any upstream dosing.
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.
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
- Effects of chlorine dioxide treatments on polyamide membrane properties and filtration performance (April 2026)
Industry Standard - Journal of Environmental Chemical Engineering
External links open in a new window. ChloroKlean is not responsible for the content of external websites.