This has been known for a longer time. As early as 1976, a study was published in which salicylic acid and clofibric acid were detected in the effluent of a sewage treatment plant in Kansas City. We currently know that there are well over 1,000 substances in wastewater that pose a risk. Many others have not yet been sufficiently researched in this regard.
In current studies of water quality in European rivers by the Helmholtz Centre for Environmental Research, 610 chemicals whose occurrence or problematic effects are known were examined in more detail and analyzed to determine whether and, if so, in what concentrations they occur in Europe's flowing waters. The evaluation of 445 samples from a total of 22 rivers showed that the researchers were able to detect a total of 504 of the 610 chemicals. In total, they found 229 pesticides and biocides, 175 pharmaceutical chemicals as well as surfactants, plastic and rubber additives, per- and polyfluoroalkyl substances (PFAS) and corrosion inhibitors. In 40 percent of the samples they detected up to 50 chemical substances, in another 41 percent between 51 and 100 chemicals. In 4 samples they were even able to detect more than 200 organic micropollutants. With 241 chemicals, they detected the most substances in a water sample from the Danube.
Another relevant factor is the danger posed by the spread of multi-resistant bacteria. There are two possible ways in which this can happen through wastewater. Firstly, by transporting already resistant strains into the receiving water due to inadequate treatment technology. The other possibility is the development of resistant cultures in the environment by introducing antibiotics into the water body. Preventing the entry of bacteria has long been used as a form of hygienic treatment using UV light or ozone, especially if the water is to be reused. Membrane systems such as membrane bioreactors or downstream ultrafiltration also serve this purpose. Scientific Services, German Bundestag - Multi-resistant germs in water, research projects and studies, page 6, March 13, 2018, accessed on 6. January 2025. Depending on the intensity and technology, some micropollutants are also removed in addition to the bacteria. The extent to which membrane technologies with low energy consumption are able to deplete trace substances is being investigated.
Since 1 January 2025, there has been a recast of the Urban Waste Water Treatment Directive in the European Union, which requires the removal of a large proportion of micropollutants from wastewater. Due to the large number of amendments that have now been made, the directive was rewritten on November 27, 2024 as Directive (EU) 2024/3019, published in the EU Official Journal on December 12, and entered into force on January 1, 2025. The member states now have 31 months, i.e. until July 31, 2027, to adapt their national legislation to the new directive ("implementation of the directive").
The implementation of the framework guidelines is staggered until 2045, depending on the size of the sewage treatment plant and its population equivalents (PE). Sewage treatment plants with over 150,000 PE have priority and should be adapted immediately, as a significant proportion of the pollution comes from them followed by wastewater treatment plants with 10,000 to 150,000 PE that discharge into coastal waters or sensitive waters. The latter concerns waters with a low dilution ratio, waters from which drinking water is obtained and those that are coastal waters, or those used as bathing waters or used for mussel farming. Member States will be given the option not to apply fourth treatment in these areas if a risk assessment shows that there is no potential risk from micropollutants to human health and/or the environment. EUR-LEX - Directive of the European Parliament and of the Council Concerning Urban Wastewater Treatment (Recast) EUR-LEX - Directive (EU) 2024/3019 of the European Parliament and of the Council of 27 November 2024 concerning urban wastewater treatment (recast) (Text with EEA relevance)
In addition to that a large number of techniques are still in experimental stage. These include for example processes that work with plasma or ultrasound, so-called AOP processes, applications with zeolites and cyclodextrins, membrane processes or photocatalysis.
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