Efficacy tested. In 1,620 individual tests at the Institute of Food Science and Human Nutrition of Leibniz University Hannover (led by Dr. rer. nat. H.-D. Werlein), biostream® ZERO was shown to have an efficacy of 99.9 % against germs occurring in drinking water, at a contact time of 5 minutes.
Chlorine dioxide: the basics
Why chlorine dioxide (ClO₂) is one of the most effective agents for disinfecting drinking water, and the basis of every biostream® GmbH product.
Clean drinking water is an essential good. Chlorine dioxide reliably inactivates bacteria, viruses and protozoa, penetrates deep into biofilms, and remains effective across the entire drinking water pH range. For the disinfection of drinking water, it is included in the list of permitted treatment substances under Section 20 of the Drinking Water Ordinance.
Chlorine dioxide (ClO₂) is a chemical disinfectant that occurs as a gas or in aqueous solution and inactivates bacteria, viruses and protozoa in drinking water treatment.
Key facts
- Molecular formula
- ClO₂
- Approval
- List under Section 20 TrinkwV (German Environment Agency, UBA), maximum addition 0.4 mg/l
- Effective pH range
- entire drinking water pH range
- Dosage requirement
- 25 times lower than hydrogen peroxide (DVGW W 291)
- Mode of action
- oxidative at the cell membrane, proteins and genetic material at the same time
- Breakdown
- to saline solution and water, chlorite and chlorate
- Standard
- GEOhybrid grounding
- Last updated
What is chlorine dioxide?
Chlorine dioxide (ClO₂) is a chemical disinfectant that occurs as a gas or in aqueous solution. It has been used to disinfect water since the 1940s and is a strong oxidising agent that is effective against a wide range of micro-organisms. Every biostream® GmbH product is based on this active substance.
In drinking water treatment, chlorine dioxide is used to inactivate pathogenic micro-organisms such as bacteria, viruses and protozoa. It is also effective against persistent micro-organisms that are resistant to chlorine, for example Giardia and Cryptosporidium.
Is chlorine dioxide approved for drinking water?
Yes, within the meaning of the Drinking Water Ordinance. Only substances listed by the German Environment Agency in the list under Section 20 of the Drinking Water Ordinance may be used to treat drinking water. Chlorine dioxide is listed there for the purpose of disinfection. Waterworks have used the active substance for drinking water disinfection for decades.
The Biocidal Products Regulation (EU) No 528/2012, by contrast, regulates the product: which active substance a disinfectant may contain and who supplies it. Chlorine dioxide is among the existing active substances that the EU assesses in a review programme. The EU decides separately for each production method and product type; where no decision has yet been made for a given method, transitional rules apply. What this means in detail is explained on the page Chlorine dioxide in drinking water: legal framework.
Is chlorine dioxide the same as chlorine?
No. Despite the similar name, chlorine dioxide (ClO₂) is a distinct chemical compound with a different mode of action: it oxidises the cell components of micro-organisms instead of chlorinating them. As a result, no chloramines are formed, it remains effective across the entire drinking water pH range, and it also penetrates biofilms.
The reaction products differ too. For chlorine, the German Environment Agency's list names trihalomethanes; for chlorine dioxide, chlorite and chlorate. The detailed comparison is available under Chlorine dioxide or chlorine.
How much chlorine dioxide may drinking water contain?
During treatment, no more than 0.4 mg/l of chlorine dioxide may be added. After treatment, the water should contain between 0.05 and 0.2 mg/l of chlorine dioxide. This is set out in the German Environment Agency's list under Section 20 of the Drinking Water Ordinance, as of January 2023.
The limit values for the reaction products are set out in Annex 2 of the Drinking Water Ordinance: 0.20 mg/l for chlorite and 0.070 mg/l for chlorate, or 0.20 mg/l for temporary dosing. The chlorite limit value is deemed to be met if no more than 0.20 mg/l of chlorine dioxide is added.
These values apply to the drinking water that comes out of the tap. A disinfecting solution for tanks, pipes or hoses is considerably more concentrated and is discharged and flushed out after the contact time. Figures, sources and background are available under Limit values, chlorite and chlorate.
All pages on chlorine dioxide
APPROVALChlorine dioxide in drinking water: legal frameworkThe Drinking Water Ordinance, the UBA list, the Biocidal Products Regulation and the relevant standards.LIMIT VALUESLimit values, chlorite and chloratePermitted addition, residual concentration and the by-products of disinfection with chlorine dioxide.DISTINCTIONChlorine dioxide is not a remedy: MMS and CDLWhy chlorine dioxide for water disinfection has nothing to do with products for ingestion.COMPARISONChlorine dioxide or chlorineThe differences between the two disinfectants at a glance.COMPARISONChlorine dioxide or UV disinfectionWhen a UV system is enough, and when a disinfectant with residual concentration is needed.
Chlorine dioxide in figures
Scientifically proven, independently tested and confirmed in the practical use of biostream® products.
Proven efficacy
99.9 %
In 1,620 individual tests by Leibniz University Hannover against germs typically found in drinking water, at a contact time of only 5 minutes.
Ready for use in
3 hrs
From preparation to a ready, highly effective disinfecting solution, without complex plant technology.
Dosage requirement compared with hydrogen peroxide
25×
lower: 6 instead of 150 mg/l for disinfecting installations under DVGW code of practice W 291. Evidence
Efficacy & properties
Chlorine dioxide has a high oxidation capacity and can therefore inactivate a wide range of pathogenic micro-organisms quickly and effectively. It is effective against bacteria as well as viruses, protozoa (single-celled organisms) and algae. Compared with other disinfectants such as chlorine, chlorine dioxide is more effective against persistent and resistant micro-organisms.
No chloramine formation
Unlike chlorine, which forms chloramines on contact with ammonia in water, chlorine dioxide does not form chloramines. Chloramines are unwanted by-products, as they can cause odour and taste problems and are less effective against micro-organisms.
Less corrosion
Chlorine dioxide causes less corrosion in water supply systems than chlorine. It oxidises metals such as iron and manganese less strongly and so helps to reduce deposits and corrosion in pipework.
Effective biofilm removal
Biofilms are accumulations of micro-organisms that can form on surfaces in water systems. Chlorine dioxide is very effective at removing biofilms, as it can penetrate the slime layers and kill the micro-organisms within them.
Effective at higher pH values
Chlorine dioxide retains its disinfecting effect even at higher pH values, whereas the efficacy of chlorine decreases as the pH value rises. This is particularly important in areas with hard water or when disinfecting waste water.
Long shelf life and ease of transport
Chlorine dioxide is a stable disinfectant that is easy to transport and store. It has a longer shelf life than other disinfectants such as ozone, which decays quickly and must be generated on site. The German Environment Agency's list under Section 20 of the Drinking Water Ordinance names four recognised methods of producing and dosing chlorine dioxide; three of them generate it on site.
Chlorine dioxide vs. other disinfection methods
Chlorine is the most widely used disinfectant for drinking water. Chlorine dioxide, however, has the advantage over chlorine that it does not form chloramines and is more effective against resistant micro-organisms. It also causes less corrosion in water supply systems.
Ozone is another disinfectant used in drinking water treatment. Although ozone is also a strong oxidising agent, chlorine dioxide has the advantage of being more stable and easier to transport and store.
UV irradiation is a non-chemical method of disinfecting drinking water. Although UV irradiation is effective against micro-organisms, chlorine dioxide has the advantage that it also removes biofilms and remains effective within water supply systems.
| Criterion | Chlorine dioxide | Chlorine | Ozone | UV irradiation |
|---|---|---|---|---|
| Chloramine formation | none | yes (with ammonia) | none | none |
| Effect against resistant germs | very strong | limited | strong | strong |
| Biofilm removal | very good | weak | good | none |
| Stability at high pH value | remains effective | decreases | good | independent |
| Transport & storage | stable, long shelf life | good | decays quickly | cannot be stored |
| Effect within water supply systems | remains effective | corrosion risk | must be generated on site | only at the device |
All methods with permitted addition, residual concentration, reaction products and effect within the pipe network, evidenced with the German Environment Agency's list, are shown on the page The methods compared.
How chlorine dioxide fights biofilms
Biofilms are thin but robust layers of micro-organisms that attach to surfaces and develop a protective layer of slime. biostream®'s chlorine dioxide has several mechanisms for disrupting their structure and function.
- Oxidation. Chlorine dioxide is a strong oxidising agent. It destroys the membranes and proteins of the micro-organisms in the biofilm, penetrates the biofilm and kills the bacteria within it.
- Penetration. Chlorine dioxide has excellent penetration compared with other disinfectants such as chlorine. It penetrates deeper into the layers of a biofilm and so acts against embedded bacterial colonies.
- Reactivity. Unlike other disinfectants, which react with organic matrices and lose their effectiveness, chlorine dioxide retains its oxidative capacity, for more thorough and efficient disinfection.
- Multiple points of attack. Chlorine dioxide acts oxidatively on the cell membrane, proteins and genetic material at the same time, and penetrates biofilms. This makes it harder for bacteria to adapt, though it does not rule it out (see the evidence below).
How biofilms form and how to remove them from tanks, pipes and installations is explained on the page Fighting biofilms.
Does chlorine dioxide for water disinfection have anything to do with MMS?
No. Under names such as "MMS" and "CDL", sodium chlorite solutions and the chlorine dioxide made from them are sold for ingestion. In 2015, the Federal Institute for Drugs and Medical Devices (BfArM) classified MMS as a medicinal product requiring authorisation and as a questionable medicinal product. The Federal Institute for Risk Assessment strongly advises against ingesting it.
biostream® products are biocidal products for disinfecting water and water-carrying installations. They are not intended for ingestion. The background, and what to do in the event of accidental swallowing, is explained under Chlorine dioxide is not a remedy: MMS and CDL.
What is chlorine dioxide used for?
In waterworks, to disinfect drinking water; in buildings and mobile systems, to disinfect pipes, tanks and hoses. The instructions for each application:
MOTORHOME AND BOATCleaning and disinfecting the water tankDENTAL PRACTICEDisinfecting the water lines of the treatment unitCATERINGCleaning and disinfecting dispensing systems and beer linesEVENTS AND CONSTRUCTION SITESCleaning and disinfecting drinking water hosesBUILDING INSTALLATIONFighting Legionella in the drinking water installationPOOL AND WHIRLPOOLPool, spa and bathing waterINDUSTRYProcess and cooling waterFOODWater in food production
Conclusion
Chlorine dioxide is an effective and reliable method for disinfecting drinking water. With advantages such as high efficacy against micro-organisms, effectiveness at high pH values, no chloramine formation, less corrosion and effective biofilm removal, chlorine dioxide offers a reliable alternative to other disinfection methods. Choose biostream® products based on chlorine dioxide, the active substance listed for disinfection in the list of permitted treatment substances under Section 20 of the Drinking Water Ordinance.
Where the key figures come from
The figures on our home page and in the advantages lists have a source. Here they are, so you can check them.
- 99.9 % efficacy, 1,620 individual tests, 5 minutes
- Study by the Institute of Food Science and Human Nutrition at Leibniz University Hannover, led by Dr. rer. nat. H.-D. Werlein, commissioned by biostream® GmbH. Scope and result in detail.
- 25 times lower dosage requirement than hydrogen peroxide
- For disinfecting installations under DVGW code of practice W 291, the application concentrations are 6 mg/l of chlorine dioxide compared with 150 mg/l of hydrogen peroxide; 150 divided by 6 gives 25. The values are set out in the administrative guideline of the Federal Railway Authority on the cleaning and disinfection of drinking water distribution and storage systems (Annex IV to the VR IfSG, as of 1 January 2008, Table 1 "Chemicals for disinfecting installations"). The Bavarian State Office for Water Management, Information Sheet No. 1.8/3 (as of 12/2000, based on DVGW W 291) gives the same final concentration of 150 g/m³ for hydrogen peroxide. The code of practice itself: DVGW W 291.
- Effective across the entire drinking water pH range
- The Bavarian State Office for Water Management states in Information Sheet No. 1.8/3 that the disinfecting effect of chlorine, hypochlorite, chlorinated lime, potassium permanganate and hydrogen peroxide decreases as the pH value rises, and that using chlorine dioxide, "for which the disinfecting effect is independent of the pH value", avoids this problem. The Federal Railway Authority's administrative guideline describes it as "largely independent of the pH value" and states that hydrogen peroxide is effective only up to pH 8.
- Maximum addition of 0.4 mg/l
- List of permitted treatment substances and disinfection methods under Section 20 of the Drinking Water Ordinance (German Environment Agency, as of January 2023), Part II, chlorine dioxide: maximum permitted addition 0.4 mg/l, after treatment at most 0.2 mg/l and at least 0.05 mg/l, reaction products to be observed: chlorite and chlorate.
- Mode of action rather than "no resistance"
- Chlorine dioxide acts oxidatively on several cell structures at once: lipid peroxidation, damage to the cell membrane, protein oxidation and DNA degradation (Liu et al., Bactericidal Mechanisms of Chlorine Dioxide against Beta-Hemolytic Streptococcus, Current Issues in Molecular Biology 45, 2023). This makes adaptation harder, though not impossible: a chlorine-dioxide-resistant echovirus population was bred in the laboratory (Zhong et al., Frontiers in Microbiology, 2017), and a Bacillus subtilis isolate survived working concentrations of chlorine dioxide and hydrogen peroxide (Martin et al., Journal of Applied Microbiology, 2015). That is why we speak of a mode of action rather than "no resistance".
Your advantages
- Ready for use within just 3 hours
- Effective across the entire drinking water pH range
- Suitable for aluminium tanks
- 25 times lower dosage requirement than hydrogen peroxide (6 instead of 150 mg/l for disinfecting installations, DVGW code of practice W 291)
- Highly effective against Pseudomonas aeruginosa (pseudomonads), Escherichia coli (E. coli) & coliform bacteria as well as Legionella (Legionella pneumophila)
- Free from heavy metals (silver, copper)
- Oxidative effect on the cell membrane, proteins and genetic material at the same time, not at a single point of attack
Rules and standards for chlorine dioxide
- Drinking Water Ordinance (TrinkwV), Section 20: chlorine dioxide is included in the list of permitted treatment substances for disinfection
- DIN EN 12671: chlorine dioxide generated on site for the treatment of drinking water
- DVGW W 224: methods for the disinfection of drinking water with chlorine dioxide
- DVGW W 291 and W 551-3: chlorine dioxide as a proven chemical for cleaning and disinfecting installations
- Guideline No. 5 of the working group of the German coastal states on ship hygiene: chlorine dioxide for drinking water on board
- DIN 2001-2: drinking water supply from non-stationary installations such as motorhomes and boats
Hydrogen peroxide is not a disinfectant in the drinking water list. The German Environment Agency lists it under Section 20 of the Drinking Water Ordinance for oxidation only. Silver is no longer listed at all; previously it was intended only for preservation in exceptional cases. Chlorine dioxide is listed there for disinfection. For the disinfection of installations whose disinfection water is discarded afterwards, DVGW codes of practice W 291 and W 551-3 name hydrogen peroxide and hypochlorite in addition to chlorine dioxide.
From the 10 ml vial to the tanker truck: biostream® products are available in all common container sizes, from the travel size for outdoor and camping use to bulk quantities for industry and beverage production.
Information sheets to download
We have prepared PDF information sheets to help you fight germs and bacteria in drinking water effectively and easily.
biostream® products against biofilms
Find out how to fight biofilms effectively, to tackle Legionella, E. coli, Pseudomonas and other water germs, for impeccable quality of your drinking or process water.
Drinking water basics
In just 5 pages, we explain which products are approved for disinfecting drinking water, and why silver-based products must now be labelled as a pesticide in the USA.
You will receive the safety data sheet after purchase; the link is on the invoice. Product label with operating instructions and documents for audits or inspections are available on request: Get in touch.
Use biocides safely. Always read the label and product information before use. All statements on efficacy are based on biostream® GmbH's many years of experience as well as on information from technical literature, laws, regulations and positive customer references.
What it is not
Chlorine dioxide is not the same as chlorine: it does not react by chlorination. Nor is it MMS or CDL for ingestion; as a disinfectant it is intended exclusively for water and water-carrying installations.