Depending on the degree and kind of water pollution there are different technologies available to meet these demands and to produce pure water. The Austrian Research Centre Seibersdorf is accounting for these issues by different activities within the special business branch of water technology and stresses thus the international topicality of the subject "water".

The tasks in water treatment technology have changed in the course of decades. According to Dipl-Ing. Manfred Kirchebner, head of the department "Water Technology" of the Research Centre Seibersdorf, the main tasks of today are the "elimination of anthropogenic, high-molecular organic contaminants, such as chlorinated hydrocarbons, pesticides, etc. and disinfectants waters contaminated with bacteria and viruses".

"Especially nitrates (limit value 50 mg/l, approximate value 25 mg/l), pesticides/plant protection agents, halogeneous hydrocarbons, organic pollutants, as well as bacteria and viral contaminants are problematic in water treatment", says Dipl.-Ing. Monika Schönerklee of the Research Centre Seibersdorf. The elimination of nitrates in particular is becoming increasingly important due to the nitrate ordinance and the Nitrate Directive of the EU. Avoidance strategies in agriculture, which is certainly one of the main polluters, will have positive effects only in a couple of years.

The scientists of Seibersdorf hold a leading position in the development of new technologies and processes. In the trial phase, for example, is a process of catalytic nitrate reduction - a residual-free process with hydrogen as a reducing agent. Also developed in the labs of the Research Centre Seibersdorf was the ozone-electron beam procedure for the elimination of pesticides and other organic contaminants, as well as for disinfection. The advantage compared to other oxidation procedures is the production of a high OH-yield of radicals for the decomposition of harmful components.

Nitrates threaten our health

"A high nitrate concentration in drinking water can affect human health when regularly consumed. On the one hand, it can lead to cyanosis in babies, on the other, nitrates can be converted in carcinogen nitrosamines in the course of digestion", explains Dieter Hölzli, in charge of the technology and marketing division of the UV-Technologie of the BWT (Best Water Technology) in Mondsee, Austria.

Austrian companies like the BWT in Mondsee, the Phillip Müller company in Vienna, or the WABAG, a subsidiary of the VA Tech, are leading in the field of water treatment plants and operate internationally. Every year, several million ATS are being spent for the development of new procedures and the improvement of existing water treatment technologies.

In agricultural regions in particular, drinking water is heavily polluted by nitrates. How extreme this nitrate concentration can be is shown by the example of a condominium in Marchegg in Lower Austria. With 100 mg/l the water engineers found a concentration of twice the legal limit value. "A complicated combination of multiple-step filtration, reverse osmosis and ion exchange is reducing the nitrate concentration in drinking water to 16 mg/l", describes the BWT water expert Hölzli the technical masterpiece. An additional positive side effect of this water treatment plant tailored to suit this situation is the reduction of water hardness. An integrated UV-disinfection device guarantees that the water is not only pure in a chemical, hygienic and bacteriological sense, but it also tastes good.

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New ways: Electrodialysis for drinking water purification

The principle of electrodialysis for the desalination of water has been used by the WABAG for the development of the ENR-procedure. This technology is especially suited for the elimination of nitrate from drinking water and it also makes the water softer, which is a pleasant side effect. The principle of electrodialysis is the separation of salts by ion exchange membranes. The driving power is an electric field.

In cooperation with universities and waterworks the WABAG has developed the ADOX procedure, which is used for eliminating pesticides and for cleaning heavily polluted groundwater. "Pollutants in water are mineralised by advanced oxidation and mainly split into carbonic acid, chloride and water. The principle of the ADOX procedure is based on the combined use of the oxidising agents ozone (O₃) and hydrogen peroxide (H₂O₂). Hydrogen peroxide increases the oxidative effect of ozone by producing OH-radicals", explains Dr. Florian Hell of the WABAG. The subsequent procedure indispensable in water treatment is done by an active coal filter on a biological basis. The last phase is a safety disinfection.

Ultrafiltration is becoming more and more important in water treatment. Large plants with huge capacities are supplying excellent drinking water quality today. Dr. Hell calls the ultrafiltration plant in Hermeskell in the Palatinate, which is part of a drinking water treatment plant, a perfect example for this technology. With a total turnover of 1400 cubic metres per hour and four lines this fully-automatic plant has an enormous capacity.

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New developments in the project stage

The preliminary treatment of raw water consists of a CO₂-dosage with subsequent marble filters. After a coarse filtration the particles, bacteria and parasites are completely eliminated by ultrafiltration. In the next stage iron, manganese and aluminium are eliminated. The rinsing of the ultrafiltration is done by permeate with a partial addition of hydrogen peroxide. Ozone is an alternative to UV-filtration. Dipl.-Ing. Büchl of the Philip Müller GmbH in Vienna points to two fields of application for this technology in drinking water treatment: the lake water works Küsnacht-Erlenbach on the Lake of Zurich in Switzerland is working with ozone treatment. The primary aim was to avoid undesirable, partially even harmful compounds that occur by chlorinating the water. The ozone filtration is also eliminating the bad smell and taste of chlorinated water.

The waterworks in Rostock was the first water treatment plant in Germany to become equipped with ozone filtration. The result is the same as in Switzerland: healthy, good tasting water. A new way is the perfection of the so-called wet-oxidation - a photochemical process to transform harmful substances in water. This procedure affords much higher energy amounts compared to currently used technologies. On the occasion of a congress in June 2000 in the Canadian Province of Ontario industrial researchers and engineers will be discussing the possibilities of this new technology. (Source: aqua press Int. 5/99)
Dr. Alexander Tempelmayr

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Information & Contact:
BWT AG
Walter-Simmer-Straße 4
A-5310 Mondsee
Tel. +43 6232 5011-0
Fax +43 6232 4058