In the view of Hydro-Elektrik GmbH, it is impossible to manage without ozone when it comes to water treatment. Due to its wide spectrum of activity, ozone is used in water treatment for disinfection and for the environmentally friendly oxidation of inorganic and organic matter. In many drinking water plants, an ozone stage is one of the central treatment stages.

Experts are aware that under certain conditions, ozonisation can also produce small quantities of unwanted reaction byproducts. The aim of all water treatment is of course to produce drinking water that is of the optimum quality for the consumer and to minimise the unwanted substances content. Hydro-Elektrik GmbH, and indeed other plant constructors, regard the recently announced findings relating to the possible formation of the nitrosamine N-nitroso dimethylamine (NDMA) as a challenge to improve upon tried-and-tested treatment processes.

NDMA can be produced during the ozonisation of water containing
N,N dimethylsulfamide (DMSA). DMSA is a metabolite of the active agent tolylfluanide that is produced with agents used to treat plants (fungicides). According to the assessment of the Federal Environment Agency (Umweltbundesamt), there are no long-term health risks associated with the consumption over a lifetime of drinking water containing maximum levels of 0.01 micrograms/l of NDMA and
1 microgram/l of DMSA.

Initial wide-ranging tests indicate that the newly defined maximum levels have only been exceeded in individual water treatment plants under very specific conditions, and that there is an absolute need for action. Hydro-Elektrik GmbH points out that in the event of possible problem cases, there should be no hasty interventions in the process technology, because use of other oxidising agents can produce additional, previously unknown decomposition products.

Possible approaches for reducing the reaction byproducts exist, for example, in a reduction of the ozone dosage, the action time and in optimising the downstream, biologically acting filter stage. In any case however, the experience of an experienced plant constructor should be incorporated into possible plant modifications.

Contact partner Manfred Brugger