Chlorine dioxide in drinking water: approval, limits and standards
Yes, chlorine dioxide may be used to disinfect drinking water. The Drinking Water Ordinance permits only substances from the list that the German Environment Agency keeps under Section 20 (Section 19(3) TrinkwV) for use in treatment. Chlorine dioxide is listed there for the purpose of disinfection. The list also sets out how much may be added and how much may remain in the water after treatment.
Who decides what may go into drinking water?
The Drinking Water Ordinance regulates which substances may be added to drinking water. Under Section 19(3) TrinkwV, only treatment substances and disinfection methods listed under Section 20 may be used in treatment. This list is kept by the German Environment Agency and published in the Federal Gazette. The current version is dated January 2023.
Anyone who treats water with a substance that is not on the list may not supply it as drinking water under Section 22 TrinkwV. Substances other than treatment substances may not be added to drinking water at all, under Section 19(2).
What does the list say about chlorine dioxide?
The list includes chlorine dioxide in Part I c, the section for substances used for disinfection. For water supplied as drinking water, the following figures apply:
| Entry in the list | Chlorine dioxide (ClO₂) |
|---|---|
| Purpose | Disinfection |
| Purity requirements | DIN EN 12671, with details on the starting materials |
| Maximum permitted addition | 0.4 mg/l |
| Content after treatment | at most 0.2 mg/l, at least 0.05 mg/l |
| Reaction products to observe | Chlorite and chlorate |
| Chlorite | at most 0.2 mg/l; deemed to be met if no more than 0.2 mg/l of chlorine dioxide is added |
| Chlorate | 70 µg/l for continuous addition, 200 µg/l for temporary addition |
Source: List of permitted treatment substances and disinfection methods under Section 20 TrinkwV, as of January 2023 (BAnz AT 27.01.2023 B12), Part I c.
Part II of the list names four recognised ways of producing and dosing chlorine dioxide, each referring to DVGW code of practice W 224. The limit values for chlorite and chlorate are also set out in Annex 2 of the Drinking Water Ordinance. What they mean is explained on the page Limit values, chlorite and chlorate.
These values apply to water that is drunk. When disinfecting pipes, tanks and containers, known as installation disinfection, the disinfecting water is subsequently discarded and the installation is thoroughly flushed. DVGW codes of practice W 291 and W 551-3 apply to this.
What does the Biocidal Products Regulation govern?
Regulation (EU) No 528/2012, the Biocidal Products Regulation, does not regulate drinking water but 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 (Delegated Regulation (EU) No 1062/2014, Annex II). 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.
One of these rules is set out in Article 95: a biocidal product may only be made available if the supplier of the active substance or of the product is entered on the list of the European Chemicals Agency (ECHA) for the relevant product type. The statement "compliant with Article 95" is therefore a statement about the origin of the active substance, not about its efficacy.
Which standards and regulations apply to chlorine dioxide?
Each set of rules covers a different area. None replaces another.
| Regulation | What it governs |
|---|---|
| Drinking Water Ordinance (TrinkwV), Sections 19, 20, 22 and Annex 2 | Which substances are permitted in treatment and which limit values, for example for chlorite and chlorate, apply in drinking water. |
| List under Section 20 TrinkwV (German Environment Agency, as of January 2023) | Permitted treatment substances with purpose, addition, residual concentration and reaction products; chlorine dioxide for disinfection. |
| Biocidal Products Regulation (EU) No 528/2012, Article 95 | Origin of the active substance: supplier on the ECHA list for the product type. |
| DIN EN 12671 (2016-09 edition) | Products for treating water intended for human consumption: chlorine dioxide generated on site. |
| DVGW W 224 (2023-03 edition) | Methods for disinfecting drinking water with chlorine dioxide: production and use. |
| DVGW W 291 (2021-12 edition) | Cleaning and disinfection of water supply installations; names chlorine dioxide as a proven disinfecting chemical. |
| DVGW W 551-3 (2022-08 edition, replaces W 557) | Cleaning and disinfection of drinking water installations, including non-stationary systems. |
| DIN 2001-2 (2025-06 edition) | Drinking water supply from non-stationary installations, for example motorhomes, boats or festival sites. |
| DVGW W 270 and the UBA's KTW assessment basis | Materials in contact with drinking water, such as hoses; anchored in law under Sections 14 and 15 TrinkwV. |
| Guideline No. 5 of the working group of the German coastal states (2008) | Chemical disinfection of drinking water on ships; permits sodium hypochlorite, calcium hypochlorite and chlorine dioxide. |
How to correctly disinfect drinking water hoses is shown in the guide to hose disinfection.
Permitted does not yet mean effective
The two terms are often confused. A substance being on the list means it may be used. It says nothing about how well a particular product works. Conversely, proof of efficacy does not replace approval. How we prove the efficacy of biostream® ZERO is explained on the page Proof of efficacy.
Frequently asked questions about approval
Is chlorine dioxide approved for drinking water?
Chlorine dioxide is included in the list of permitted treatment substances and disinfection methods under Section 20 of the Drinking Water Ordinance, for the purpose of disinfection. Only substances from this list may be used in the treatment of drinking water.
How much chlorine dioxide may remain in drinking water?
After treatment, at most 0.2 mg/l and at least 0.05 mg/l, with an addition of at most 0.4 mg/l. This is set out in the list under Section 20 TrinkwV. For the reaction product chlorite, a maximum value of 0.2 mg/l applies.
Is hydrogen peroxide approved for drinking water disinfection?
In the list under Section 20 TrinkwV, hydrogen peroxide appears only in the part for general treatment substances, for the purpose of oxidation. It is missing from the part for disinfection substances. For disinfecting installations, after which the water is discarded, DVGW codes of practice W 291 and W 551-3 name hydrogen peroxide alongside sodium hypochlorite and chlorine dioxide.
Is silver still permitted?
Silver no longer appears in the current list under Section 20 TrinkwV; it was removed by 2019 at the latest. Earlier versions permitted silver only for preserving stored water, in exceptional cases without systematic use. Even there, it was never a disinfectant.
Is there an EU Drinking Water Ordinance?
No. At European level, the Drinking Water Directive (EU) 2020/2184 applies. Germany implemented it through the Drinking Water Ordinance of 20 June 2023. For operators in Germany, the Drinking Water Ordinance is the authoritative instrument.
What documents do I get from biostream?
For hygiene documentation, audits and submissions to authorities, we provide the safety data sheet, the product label with operating instructions, and details of the rules that apply to your application. If you need a particular document for a tender or an inspection, get in touch with us.
Sources
- German Environment Agency: list of permitted treatment substances and disinfection methods under Section 20 TrinkwV, as of January 2023
- Drinking Water Ordinance, Section 20 and Annex 2
- Regulation (EU) No 528/2012 concerning biocidal products
- DIN EN 12671:2016-09 at DIN Media
What this page does not cover: This page is not a substitute for legal advice or for information from the competent authority. In individual cases, the product label, the operating instructions and the applicable version of the regulations named are authoritative.