ChloroKlean BPR Compliant Chlorine Dioxide Disinfectant - UK Supplier

Chlorine Dioxide vs Ozone for Cooling Towers and Drinking Water

Chlorine dioxide (ClO₂) and ozone (O₃) are both strong oxidising biocides used in cooling tower and drinking water treatment. Ozone has a higher oxidation potential and is highly effective at the point of dosing, but has a half-life of around 20 minutes in water and leaves no measurable residual, so secondary disinfection is still required throughout the distribution system. Ozone also forms bromate (a regulated by-product) when bromide is present in the source water (WHO and US EPA guidance). Chlorine dioxide provides a sustained, measurable residual at pH 4-10, penetrates biofilm, does not form trihalomethanes (THMs) or bromate, and avoids the capital cost of on-site ozone generation. For UK cooling towers under HSG274 and for distributed potable water systems, ClO₂ is normally the more practical choice. ChloroKlean Plus L20 is BPR-compliant for PT5 (drinking water) and PT11 (cooling system preservation).

Author
Key Advantage of ClO₂
Provides a sustained, measurable residual across the whole distribution system; ozone does not.
By-products
ClO₂ produces no THMs, HAAs, or bromate. Ozone forms bromate where bromide is present, plus aldehydes and ketones from organic matter.
pH Range
ClO₂ effective at pH 4-10. Ozone effective but consumed faster at higher pH and elevated temperatures.
Regulatory Sources
WHO Guidelines for Drinking-water Quality, HSE HSG274 Part 1, US EPA Stage 1 D/DBPR, DWI guidance, EU BPR 528/2012
UK Compliance
Both can be used under UK GB BPR with correct PT5/PT11 authorisation. ChloroKlean Plus L20 is fully BPR-compliant for water treatment applications.
Comparison Guide

Chlorine Dioxide vs Ozone

Comparing chlorine dioxide (ClO₂) and ozone (O₃) for cooling towers, drinking water, and industrial water treatment. Residual disinfection, capital cost, and bromate formation all matter.

ClO₂

Chlorine Dioxide

  • Sustained residual across distribution system
  • Penetrates biofilm in fill packs and pipework
  • No bromate formation in bromide-containing water
  • No on-site generator required - lower capital cost
  • Effective across pH 4-10
O₃

Ozone (O₃)

  • Highest oxidation potential of common biocides
  • Fast point-of-dose efficacy
  • No residual - secondary disinfection still required
  • Forms bromate when bromide is present in source water
  • High capital cost (on-site generator required)

Detailed Comparison

Detailed comparison of chlorine dioxide versus ozone
FeatureChlorine DioxideOzone
Residual Disinfection

Yes

Measurable residual across distribution

No

Half-life ~20 minutes in water

Biofilm Penetration

Excellent

Penetrates EPS matrix

Surface only

Reacts too fast to diffuse into biofilm

Bromate Formation

None

Does not oxidise bromide to bromate

Yes

Regulated DBP in bromide-containing water

THM / HAA Formation

None

Does not chlorinate organics

None

Forms aldehydes/ketones instead

Capital Cost

Low

Liquid biocide, simple dosing pump

High

On-site generator and contactor required

Energy Use

Low

No on-site generation

High

Continuous electrical generation

Legionella Efficacy

Proven

>4-log reduction documented

Proven at point of dose

But no downstream residual protection

pH Range Effectiveness

pH 4-10

Performance largely independent of pH

Reduced at high pH

Faster decomposition above pH 8

UK BPR Status

PT5/PT11 Compliant

Full GB BPR compliance

PT5/PT11 Available

Also requires PT authorisation

When to Choose Each

Choose Chlorine Dioxide When:

  • You need a measurable residual across long pipe runs
  • Biofilm control in cooling tower fill packs is essential
  • Source water contains bromide and you need to avoid bromate
  • Capital budget rules out an on-site ozone generator
  • ACoP L8 / HSG274 compliance with continuous biocide is required
  • Multiple distributed dosing points need simple, reliable injection

Consider Ozone When:

  • Single point-of-dose application with no distribution network
  • Removal of taste, odour, and colour at a treatment works
  • High organic load requiring strong oxidation before filtration
  • Capital budget for a generator and contactor is available
  • A secondary residual disinfectant is already in place downstream
"Ozone is a phenomenal oxidiser at the point of dosing - but the moment treated water leaves the contactor, you have no protection against biofilm regrowth. In a UK cooling tower running under ACoP L8, that's the wrong trade-off. Chlorine dioxide gives you the same biocidal kick, a measurable residual at every sample point, and none of the bromate risk that comes with ozonating bromide-containing make-up water."
GO

Gavin Owen, Managing Director, ChloroKlean

BPR-compliant disinfection specialist

Why Choose ChloroKlean Plus L20

If you're considering switching to chlorine dioxide, ChloroKlean Plus L20 is purpose-built for industrial and commercial applications.

BPR PT5 / PT11 Compliant

ChloroKlean Plus L20 holds full UK GB BPR compliance for drinking water (PT5) and cooling system preservation (PT11). Direct replacement for ozone in distributed systems.

Regenerative ClO₂ Chemistry

Stabilised, regenerative formulation delivers sustained antimicrobial action at low doses (0.1-0.5 ppm). No on-site generator, no contactor, no ozone destruction unit.

Independently Tested

BS EN 13623:2020 testing confirms >4-log Legionella reduction in cooling water. Documented biofilm penetration in field installations where ozone left residual fouling.

Regulatory and Scientific References

This comparison is informed by the following authoritative sources. Always refer to the latest published guidance.

WHO Guidelines
World Health Organization (WHO)

Guidelines for Drinking-water Quality: Chlorine Dioxide

WHO recognises chlorine dioxide as an effective drinking water disinfectant that does not form trihalomethanes, haloacetic acids, or bromate.

View source
HSE HSG274 Part 1
Health and Safety Executive (HSE)

Legionnaires' disease: Technical guidance for cooling towers

HSG274 Part 1 sets out the technical requirements for biocide selection and residual maintenance in cooling tower systems.

View source
US EPA D/DBPR
US Environmental Protection Agency

Stage 1 and Stage 2 Disinfectants and Disinfection Byproducts Rules

EPA D/DBPR sets limits on bromate (10 µg/L) and other regulated by-products formed during ozonation of bromide-containing source water.

View source
DWI Guidance
Drinking Water Inspectorate (DWI)

List of approved products and chemicals for use in public water supply

The DWI maintains the list of approved chemicals for treatment of water destined for public supply in England and Wales, including chlorine dioxide formulations.

View source
EU BPR 528/2012
European Parliament and Council

Biocidal Products Regulation

Both chlorine dioxide and ozone require PT5 (drinking water) or PT11 (cooling system) authorisation under the UK GB and EU BPR.

View source

Frequently Asked Questions

Replace Ozone with a Simpler, Compliant Alternative

ChloroKlean Plus L20 delivers BPR-compliant, residual chlorine dioxide for cooling towers and drinking water - without the capital cost or complexity of an ozone generator.