Chlorine dioxide (ClO₂) is an oxidising biocide used in labelled water and surface applications. Efficacy depends on the product, target organism, concentration, contact time and conditions. It forms no chloramines and generally very little THM or HAA; chlorite and chlorate require control and measurement.
Reviewed by Gavin Owen, Managing Director, ChloroKlean. Confirm use and dosing against the product label, applicable guidance and a site-specific risk assessment.
Chlorine dioxide disinfects by selective oxidation: it strips electrons from the cell walls and key proteins of microorganisms, causing rapid cell death. Because it oxidises rather than chlorinates, it behaves very differently from traditional chlorine.
Chlorine dioxide is an oxidising biocide that acts on microbial cell components. Its by-product profile depends on product purity, dose and water chemistry; chlorite, chlorate and other by-products require control.
ClO₂ can act on biofilm matrices under validated product-label conditions. Results depend on cleaning, concentration, contact time, demand and verification.
Its activity is generally less pH-dependent than free chlorine, but the validated range and efficacy conditions are product-specific.
Chlorine dioxide forms no chloramines and generally very little THM or HAA. Chlorite, chlorate and other by-products require control through dosing and measurement.
Chlorine dioxide is not the same as chlorine. It is a more selective oxidiser, is generally less pH-dependent than free chlorine and can act on biofilm under validated conditions. It forms no chloramines and generally very little THM or HAA, while chlorite and chlorate require control.
For a side-by-side breakdown of efficacy, by-products, pH range and cost, see the full comparison.
Chlorine dioxide is authorised across several Biocidal Products Regulation (BPR) product types and used throughout UK water treatment, healthcare, leisure and food sectors.
Potable-water treatment uses where the product label covers the target organisms and conditions.
PT11 includes open and closed cooling/process systems. Assess ChloroKlean Plus L20 only where current label and technical documents support the use, considering design, inhibitors, glycol, materials, operating conditions, dosing and monitoring. No routine recommendation for inhibited closed heating/chilled-water loops without expressly supported current instructions and written compatibility evidence; assess external evaporative spray water separately from the enclosed process loop.
Slime and biofilm control in paper mills, biogas plants and other industrial process water systems.
Surface and water disinfection in swimming pools, spas and public leisure environments.
Safe use depends on selecting a product with a lawful GB BPR supply route, including any applicable transitional route, for the intended use; following its label and Safety Data Sheet; controlling exposure; and verifying relevant residual and by-product limits.
Use only a suitable PT5 product and follow its label plus the applicable drinking-water regime.
Activity is less pH-dependent than free chlorine, but efficacy still requires product-specific validation.
Forms no chloramines and generally very little THM or HAA; chlorite and chlorate require control.
This article references guidance from the following authoritative sources:
WHO - World Health Organization
HSE - Health and Safety Executive
HSE - Health and Safety Executive
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ChloroKlean is a UK principle stockist of BPR-compliant chlorine dioxide products. Contact our team for product selection and dosing guidance.