Chlorine and chlorine compounds

Chlorine and chlorine compounds - indispensable for healthy water

For more than a century, the use of chlorine to disinfect drinking and bathing water has ensured that people all over the world are supplied with hygienically safe water. Chlorine disinfection is the world's most widely used process for the reliable disinfection of water. 

Chlorine and chlorine dioxide are also very useful when the systems in the waterworks or the water distribution network have to be disinfected. Due to the so-called depot effect of chlorine, it is added in many countries by the supply companies in order to protect the treated drinking water from re-germination on its long way to the consumer. Chlorine is also used in swimming pools because of this depot effect. Also when using domestic ion exchanger systems, which reduce the hardness of the drinking water, regular disinfection must be carried out as a preventive measure. This is done automatically using chlorine.


Technical officer - Water department
Dipl.-Ing. (FH) Aharon Weiß, M.Sc.

+49 172 8826912

Application of chlorine

Although chlorine dioxide is a chlorine compound, both substances have very different disinfecting effects. Chlorine acts by means of hypochlorous acid on the proteins of pathogens and denatures them. Chlorine dioxide in turn oxidizes the cell membrane of pathogens. Disruption describes the decomposition of organisms. 

In addition to the dosing of pure chlorine as chlorine gas and the use of hypochlorite solutions, in-situ devices (Latin: in-situ = on-site) are increasingly being used today. These in-situ devices generate chlorine from precursor substances such as sodium chloride by electrolysis. Chlorine dioxide is mainly produced on site because it is very unstable as a compound. The most common production processes are the mixing of sodium chlorite (a salt of chlorous acid) with either hydrochloric acid or chlorine. Stabilized disinfectants containing chlorine dioxide have now also established themselves on the market as barrel products.

Approval of chlorine and chlorine dioxide under the Biocidal Products Regulation ("BPR")

Chlorine and chlorine dioxide are biocides and are subject to Regulation (EU) No. 528/2012, the so-called Biocidal Products Regulation. Gaseous chlorine and chlorine produced in-situ are regarded as different biocidal products and are subject to their own approval procedures.

The ISA Consortium managed by figawa Service GmbH prepares the approval procedure for in-situ produced chlorine from sodium chloride by electrolysis according to Case Type 4. figawa also supports the approval process for chlorine produced in-situ from sodium chloride by electrolysis according to Case Type 2, as well as the in-situ processes chlorine dioxide produced from sodium chlorite by acidification, oxidation and electrolysis. 

Thus fundamental clarifications for the approval are brought about, the standardization work is actively supported and proportionately financed and the interests of the members are represented towards external consortia, the Commission and the European Chemicals Agency ECHA. 

Standardisation work on chlorine

In addition to the current revision of DIN 19606 "Chlorinators for water treatment - Equipment, installation and operation", standards are currently being developed for the in-situ generation of chlorine and chlorine dioxide with the aim of establishing these as European standards and supporting the approval procedure in accordance with the Biocidal Products Regulation.

The members of the figawa working group on chlorine and chlorine compounds are responsible for this. In addition to developing and revising the equipment standards, the members are active in standardising the analysis methods for chlorine by-products, the relevant product standards and the DVGW documents for use.