ChloroKlean BPR Compliant Chlorine Dioxide Disinfectant - UK Supplier

    Chlorine Dioxide vs Chloramine for Drinking Water Systems

    Chlorine dioxide (ClO₂) and monochloramine (NH₂Cl, commonly called 'chloramine') are both used as secondary disinfectants to maintain residual protection through drinking water distribution networks. Chloramine is favoured for its low THM and HAA formation and its persistent residual, but has well-documented drawbacks: it supports nitrifying bacteria (which can deplete the residual and degrade water quality), it can form N-nitrosodimethylamine (NDMA, a regulated carcinogen), it is corrosive in some plumbing materials (notably lead-soldered joints and certain elastomers), and it must be removed before kidney dialysis or aquarium use. Chlorine dioxide provides a measurable residual without forming THMs, HAAs, or NDMA, penetrates biofilm in distribution pipework, and is more effective against Legionella and Giardia (neither chemistry is a reliable Cryptosporidium barrier). For UK water systems regulated under DWI guidance and ACoP L8, ClO₂ is increasingly specified where chloramine's nitrification or NDMA risks are unacceptable. ChloroKlean Plus L20 is BPR-compliant for PT5 (drinking water) applications.

    Author
    Key Advantage of ClO₂
    Provides residual without forming NDMA, supporting nitrifying bacteria, or threatening dialysis patients. Stronger biofilm penetration.
    By-products
    ClO₂ produces chlorite and chlorate at regulated low levels. Chloramine produces NDMA (regulated as carcinogenic), some THMs/HAAs, and supports formation of nitrate via nitrification.
    pH Range
    ClO₂ effective at pH 4-10. Chloramine effective pH 7-9; outside this range monochloramine speciation shifts to dichloramine and trichloramine.
    Regulatory Sources
    WHO Drinking-water Guidelines, US EPA Stage 2 D/DBPR, DWI Regulation 31, EU BPR 528/2012 PT5, HSE HSG274 Part 2
    UK Compliance
    Chlorine dioxide is widely used in UK distribution. Chloramine is less common in the UK than the US but is permitted; both are PT5-listed under GB BPR. ChloroKlean Plus L20 is fully BPR-compliant for PT5.
    Comparison Guide

    Chlorine Dioxide vs Chloramine

    Chloramine is used as a secondary disinfectant for distribution residual, but it supports nitrifying bacteria, can form NDMA (a regulated carcinogen), and is unsafe for kidney dialysis without removal. ClO₂ avoids all three issues.

    ClO₂

    Chlorine Dioxide

    • No NDMA, THMs, or HAAs at typical doses
    • Penetrates biofilm in distribution pipework
    • Effective against Legionella; better than chlorine against Giardia (Cryptosporidium still needs UV or filtration)
    • Does not support nitrifying bacteria growth
    • Safe for systems supplying dialysis or aquaria
    NH₂Cl

    Monochloramine

    • Persistent residual across long distribution networks
    • Lower THM and HAA formation than free chlorine
    • Supports nitrifying bacteria - residual depletes
    • Forms NDMA (regulated carcinogen)
    • Must be removed for dialysis and aquaria

    Detailed Comparison

    Detailed comparison of chlorine dioxide versus chloramine
    FeatureChlorine DioxideChloramine
    NDMA Formation

    None

    Does not nitrosate dimethylamine

    Yes

    Regulated carcinogen; EPA limit 10 ng/L (proposed)

    THM / HAA Formation

    None at dose

    Does not chlorinate organics

    Low

    Lower than free chlorine but not zero

    Nitrification Risk

    None

    No ammonia released into water

    High

    Releases ammonia; nitrifiers consume residual

    Biofilm Penetration

    Excellent

    Diffuses into and oxidises EPS matrix

    Moderate

    Better than free chlorine; less than ClO₂

    Legionella Efficacy

    Proven (>4-log)

    Sub-ppm residual sufficient

    Limited

    Slow kinetics; biofilm Legionella often survives

    Cryptosporidium Efficacy

    Limited

    Inactivates oocysts only at high CT; DWI does not accept ClO₂ as a Cryptosporidium barrier in private supplies

    Very limited

    Chloramine ineffective at practical CT values

    Dialysis Compatibility

    Direct safe use rare

    ClO₂ also requires removal for dialysis

    Removal required

    Must be removed pre-dialysis; haemolysis risk

    Lead Plumbosolvency

    Low effect

    Minor impact on lead release

    Significant

    Implicated in lead release events (e.g. Flint, MI)

    UK BPR PT5 Status

    Compliant

    Supplied under GB BPR for PT5 (transitional arrangements)

    Compliant

    Also approved active substance under PT5

    When to Choose Each

    Choose Chlorine Dioxide When:

    • Source water has nitrification history or precursors
    • NDMA compliance is marginal or under regulatory scrutiny
    • Hospital, healthcare, or dialysis facility is on the network
    • Existing distribution has documented biofilm or Legionella issues
    • Lead service line replacement is incomplete (plumbosolvency risk)

    Consider Chloramine When:

    • Very long distribution networks requiring extended residual
    • Existing utility chloramination programme is well established
    • Source water has high TOC making free chlorine THM-prone
    • No dialysis or aquarium customers on the network
    • Local regulator specifies chloramine as the secondary disinfectant
    "Chloramine has a real advantage in residual persistence over very long distribution networks - that is the reason US utilities adopted it. The trade-off is the nitrification cycle and NDMA formation, both of which have become regulatory and operational headaches. Chlorine dioxide gives you most of the residual benefit without the nitrification or NDMA risk, and it actually goes after biofilm rather than passing over it. For UK water systems where Legionella and biofilm control are paramount, ClO₂ is the better fit."
    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 Compliant

    ChloroKlean Plus L20 holds UK GB BPR PT5 compliance for drinking water disinfection. Documented compliance pathway for use in private water supplies and as a secondary residual in distribution.

    No NDMA, No Nitrification

    ClO₂ chemistry does not release ammonia, so it does not feed nitrifying bacteria or form NDMA - two of the most common reasons utilities move away from chloramination.

    Biofilm and Legionella

    Independently tested >4-log Legionella reduction at 0.1-0.5 ppm. Penetrates pipework biofilm where chloramine and free chlorine sit at the surface.

    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 (Chloramines and Disinfectants)

    WHO Guidelines compare chloramine and chlorine dioxide as residual disinfectants, noting chloramine's role in NDMA formation and the nitrification risk in distribution systems.

    View source
    US EPA UCMR / NDMA
    US Environmental Protection Agency

    Unregulated Contaminant Monitoring Rule (NDMA)

    EPA's UCMR programme has tracked NDMA occurrence in US drinking water; chloramination is the dominant precursor pathway. A formal NDMA MCL is under proposal.

    View source
    DWI Guidance
    Drinking Water Inspectorate (DWI)

    Drinking Water Inspectorate - Disinfection Guidance

    DWI guidance on secondary disinfection in UK public supply lists approved chemicals including chlorine dioxide; chloramination is permitted but uncommon in the UK.

    View source
    US EPA Stage 2 D/DBPR
    US Environmental Protection Agency

    Stage 2 Disinfectants and Disinfection Byproducts Rule

    EPA Stage 2 D/DBPR triggered widespread US utility switching from free chlorine to chloramine; subsequent NDMA and nitrification issues are driving renewed interest in chlorine dioxide.

    View source
    HSE HSG274 Part 2
    Health and Safety Executive (HSE)

    Legionella: Technical guidance for hot and cold water systems

    HSG274 Part 2 covers Legionella control in building hot and cold water systems supplied from the public mains. Biofilm penetration and residual reliability are emphasised - both areas where ClO₂ outperforms chloramine.

    View source

    Frequently Asked Questions

    Chloramine forms substantially fewer THMs and HAAs than free chlorine, which is the main reason many US utilities switched in response to EPA Stage 1 and 2 D/DBPR. The trade-off is higher NDMA formation, nitrification problems, and increased lead release where lead plumbing remains.

    Yes. Monochloramine slowly releases ammonia, which is consumed by nitrifying bacteria to produce nitrite and nitrate. This consumes the chloramine residual, can drive nitrite above drinking water limits, and degrades distribution water quality. Chlorine dioxide does not release ammonia and does not support nitrification.

    Yes, at sufficient concentrations. NDMA is classified by IARC as 'probably carcinogenic to humans'. The US EPA tracks NDMA under UCMR with chloramination as the dominant precursor pathway. ClO₂ does not form NDMA.

    Chloramine is less effective than free chlorine at oxidising and stabilising the protective lead(IV) oxide scale on the inside of lead service lines. The Flint, Michigan crisis is the best-known example. Where lead service lines remain in service, secondary disinfectant choice matters - contact ChloroKlean for guidance on transitioning legacy networks.

    Chloramine has slower kinetics against Legionella than chlorine dioxide and limited biofilm penetration. For Legionella-critical applications under HSG274 Part 2, ClO₂ has substantially stronger documented efficacy. See our hospital Legionella case study.

    Yes. Chlorine dioxide can be dosed at the treatment works to provide a residual through distribution. It is widely used in parts of Europe and permitted in UK public supply under DWI approval. Typical residuals are 0.1-0.5 ppm. Contact ChloroKlean for specification.

    Avoid NDMA and Nitrification Risks

    ChloroKlean Plus L20 delivers BPR PT5-compliant chlorine dioxide for drinking water systems - residual protection without nitrification, NDMA, or biofilm Legionella.