Micropollutants in watercourses

Trace compounds are currently the biggest challenge for watercourses. They make their way into bodies of water from wastewater treatment plants and through diffuse inputs from sources such as agriculture. The FOEN is working on strategies to lower micropollutants in bodies of water.

The quality of surface waters has improved considerably since the 1970s. Toxic substances have disappeared or were banned. However, inputs of micropollutants (trace compounds) are posing an increasing challenge for the protection of bodies of water. This is due, on the one hand, to the daily use of a large number of these compounds and, on the other hand, to the fact that even low concentrations of micropollutants can cause damage to aquatic organisms. According to current knowledge, the concentrations detected in surface waters do not harm human health. However, various studies clearly suggest that pesticide pollution is a key factor influencing the widespread lack of species diversity observed in bodies of water.

Zustand der Schweizer Fliessgewässer

This publication does not exist in English. It is available in other languages. 2016

Different pollution depending on water body size

Micropollutant pollution is widespread in the bodies of water located in intensively used areas of Switzerland's Central Plateau.

Diffuse inputs are especially problematic in small streams, where high peak loads of pollution from plant protection products and biocides can be detected after rainfall in the periods when these products are applied.

Treated water from wastewater treatment plants is problematic in medium and large bodies of water because it is diluted differently when it is introduced in them. Residues from medicines and cosmetics and other items that have not been eliminated during the wastewater treatment process make their way into bodies of water from these point sources.

Direct pollution from point sources

Most substances used in settlement areas make their way into bodies of water through a wastewater treatment plant. Wastewater from industry and commerce is either channelled directly into bodies of water through individual wastewater treatment plants or indirectly through communal wastewater treatment plants. Wastewater treatment plants still remove primarily nutrients from wastewater. Micropollutants are only partially retained, if at all, and enter into bodies of water. The installation of an additional treatment cycle should improve this situation in the coming years.

The FOEN's "Organic trace materials in surface waters" indicator shows the regions of Switzerland where appreciable organic trace compound pollution from point sources such as process chemicals, medicines, biocides, and endocrine disruptors can be expected in bodies of water. In Switzerland, over 30,000 such compounds are can be found in countless products that are used every day.

Diffuse pollution

Micropollutants also enter streams and rivers through diffuse inputs - i.e. all inputs not involving wastewater treatment plants - from sources such as agriculture, settlement areas or traffic infrastructure.

In connection with the NAWA SPEZ programme, an entire cocktail of pesticides was detected in five medium-sized watercourses. In 78% of the samples, the total pesticide concentration amounted to over 1µg/L. The limits set out in the Waters Protection Ordinance were exceeded for 31 substances. It cannot be ruled out that organisms in the bodies of water were harmed, particularly by pesticides.

Diffuse inputs should be lowered by specific measures. The Federal Council has mandated the development of an action plan on risk reduction and sustainable use of plant protection products. The action plan will focus on the issue of plant protection product inputs in bodies of water.

As part of the current revision of the Waters Protection Ordinance, there is a possibility that numeric requirements (limits) will be set out for micropollutants.

Über 100 Pestizide in Schweizer Fliessgewässern (PDF, 5 MB, 01.03.2014)Programm NAWA Spez zeigt die hohe Pestizidbelastung der Schweizer Fliessgewässer auf. Artikel aus Aqua & Gas 3/2014

Improved monitoring methods

In recent years, major advances have been made in the methods used to monitor the state of bodies of water. Since micropollutants occur in very small concentrations, relevant studies on pollution in bodies of water often resemble the proverbial search for a needle in a haystack.

Yet, while an evaluation methodology definitely exists for micropollutant levels, mandatory requirements have still not been set out in legislation. They should be set out as part of the current revision of the Waters Protection Ordinance.

Further information

Last modification 13.07.2020

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