Trace substances: How do chemicals get into water – Wikipedia

Ordinary wastewater treatment plants are often insufficient to remove some trace substances from the water. Photo: imago / Rupert Oberhäuser

Diclofenac, contrast media, benzotriazole: Many trace substances can get into our water via pain relievers or dishwashing liquid. Environmentalists and entrepreneurs want to use new ways to counteract negative impacts.

Diclofenac is widely used as a pain reliever, X-ray contrast media are used in the diagnosis and treatment of diseases, and benzotriazole is used as a rust inhibitor in protective coatings for metals and in cleaning tablets for dishwashers. These three active ingredients represent thousands of chemicals produced artificially by humans, some of which, even in the smallest concentrations, can harm organisms in the water, among other things. Since the environmental problems related to these three substances are particularly evident, so-called round tables were prepared for them at the end of 2019: As part of the Federal Government’s trace materials strategy, experts from industry, water management and environmental organizations discuss in these forums how the entry of these substances can be reduced. vehicles to the environment.

Contrast factor can be clearly reduced

The Round Tables are now coming to an end – and they seem quite successful: “A great dynamic has arisen there,” Adolf Eisentrager, of the Federal Center for Traceability of Materials in Dessau, reported at the 4th Baden-Württemberg Conference, recently in Stuttgart. Participants want to keep the round tables – despite the large workload. Industry interest in this facility is also likely to be significant because it can be used to achieve environmental benefits without legal requirements.

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An example of iodinated X-ray contrast media shows how this can be done. More than 6000 tons of this were sold in Germany in 2019. As studies have shown, their entry into water bodies can be significantly reduced if the urine of patients who have been given these substances is collected separately in bags or special toilets, treated and disposed of. This approach is being tested in pilot projects.

Another possibility is to start immediately during production, for example if the contrast agent residue that accumulates during cleaning of production facilities does not simply end up in the waste water. This is now happening at the manufacturer Bipso in Singen. There, the agents are extracted from the cleaning water and concentrated with the help of something called reverse osmosis, according to Reinhard Adam, managing director of Bipso. According to the first results, it is possible to achieve a reduction of 93 to 97 percent in the contrast media in the sewage system in this way – which corresponds to 15-16 tons per year, about half of which is iodine. According to Adam, the retained contrast agent can also be recycled in this way.

It is better to wipe off the pain ointment than to wash it off

Also in the case of diclofenac, discussions and expert consultations have already led to initial successes. This is how Thomas Hillenbrand of the Fraunhofer Institute for Systems Research and Innovation in Karlsruhe explained the results of a study commissioned by the Roundtable. Since this active ingredient is used largely in the form of ointments, its entry into the environment can be significantly reduced if the hands are first wiped with a paper towel after application to the skin before washing. An information campaign under the slogan “wipe instead of washing” should now lead to a change in behavior when using these ointments.

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As much as it is necessary to make the public and manufacturers aware of the problem of trace materials, it also became clear at the Stuttgart conference that more needs to be done in wastewater treatment plants. Here, as many of these trace materials as possible must be removed from wastewater in special disposal systems with the help of ozone or activated carbon before they reach streams, rivers and groundwater. For example, Rita Tripskorn from the Institute of Evolution and Ecology at the University of Tübingen points out that climate change will lead to more droughts and thus “clearly” lead to more pollution of water bodies with environmental chemicals. Together with the State Conservation Society, it welcomes the pioneering role of Baden-Württemberg in the elimination of trace materials in the fourth clean-up phase.

New sewage treatment plants in the country

To date, 23 of these factories are operating in the country, and another 25 are under construction or planning. The Material Traceability Competence Center, which was established ten years ago and has now secured funding for another five years, plays an important role in this area. As Marie Launay, President of the Center, explained, the goal now is to devote more attention to research into processes in which synergistic effects can be best exploited. For example, ozone and activated carbon can be combined to eliminate traces of substances, and the simultaneous removal of trace substances and phosphorous is also an important topic in the future.

Doubtful trace substances

About 140,000 synthetics are currently used in Europe. They include pesticides, medicines, chemicals, detergents, cleaning agents or cosmetics. Some of these compounds can harm living organisms even at very low concentrations.

In an ordinary sewage treatment plant, trace substances are not removed from the wastewater at all or only to a relatively small extent. In the fourth cleaning stage, on the other hand, it can usually be disposed of more than 80 percent through special processes using ozone or activated carbon.

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