The Austrian enterprise Mediscan has taken care of this problem and is now able to present a highly efficient method to degrade these contaminants in water. Polluted water bodies can successfully be cleaned up with this procedure. Precious, hitherto unused groundwater bodies can now be used for public supply. The e-beam technology, which Mediscan has already used successfully in the sterilisation of medical equipment, can also be employed in water treatment.

Operating method

In the combined ozone/e-beam process the pollutants are degraded by OH-radicals. These highly reactive, short-lived radicals form by the impact of accelerated electrons on the water on the one hand, on the other the intermediate products forming at the same time and having a reducing effect are transformed by ozone into OH-radicals so that a pure oxidation process on the basis of OH-radicals is resulting (advanced oxidation).

The combined ozone/e-beam process has thus two different sources producing at the same time OH-radicals for the degradation of pollutants. The higher concentration of OH-radicals thus achieved is the decisive advantage of the process compared to other methods of producing OH-radicals, like, for example, ozone/UV, ozone/hydrogen peroxide and hydrogen peroxide/UV, which only have one source (ozone or hydrogen peroxide) available for the production of OH-radicals. Due to its higher concentration of OH-radicals the combined ozone/e-beam process can in many cases achieve a much more efficient degradation of pollutants than other comparable methods.

Technical advantages

• more OH-radicals than in conventional processes
• higher efficiency even in low concentration of pollutants
• high potential to degrade genotoxic compounds
• residual-free problem solution for drinking water and sewage
• no transfer of pollutants
• no increase of salt loads
• robust, insensitive to bubbles, turbidity, suspended particles and colour
• particularly suited for high throughputs
• low operational cost due to a high energy efficiency

Hazardous substance Atrazine

Due to the chemical structure of Atrazine not even the highly reactive OH-radicals are able to mineralise Atrazine completely. An oxidative treatment with OH-radicals, however, is able to degrade Atrazine to such an extent that the groundwater thus treated complies with the legal requirements of drinking water.

Conventional methods under the usual conditions are able to degrade only about 80 percent of the existing Atrazine. The higher concentration of OH-radicals of the combined ozone/e-beam process allows degradation of up to 99 percent, in final concentrations even up to below the legal limit value of 0.1 µg/l.

Genotoxic substances in groundwater

Examinations of groundwater contaminated with chlorinated solvents have shown that genotoxic substances were present in the water in addition to chlorinated hydrocarbons. Their concentration, however, was so low that it could not be traced with chemical methods. Therefore, origin, structure and concentration of these genotoxic substances are not known. In this case their genotoxic effect was only proved by means of a plant test, the so-called TRADESCANTIA (Spiderwort)-Kleinkerntest.

Since the result of the Tradescantia-test is only available after a several weeks, the activated carbon filters cannot be used for the elimination of these genotoxic substances. Furthermore, it has been found the UV-disinfection combined with activated carbon filtration often leads to an increase in genotoxic substances. Only the combined ozone/e-beam process has furnished the proof that it can completely eliminate these genotoxic substances from groundwater.
(Source: aqua press Int. 06/2000)

Information & Contact:
Mediscan GmbH.
Bad Haller Straße 34
A–4550 Kremsmünster
Tel. +43 75 83 51 52–511
Fax +43 75 83 51 52–44