Biofilter and use of robots: here is how less pollutants should reach the St. Gallen water courses

The canton of St. Gall meets a contamination by stream and advice. This is not enough for ecologists.

Adrian Lemmenmeier

Small rivers in the canton of St. Gallen can contain too many chemicals. (Image: Urs Bucher (May 28, 2019))

Small rivers in the canton of St. Gallen can contain too many chemicals. (Image: Urs Bucher (May 28, 2019))

The small streams of the canton of St. Gallen are heavily contaminated by chemicals. This has been demonstrated by a study of the Department of Water and Energy. Many of these substances are pesticides, most of which come from agriculture. The canton and the Farmers' Association of Eastern Switzerland want to make farmers more aware of this.

What does it mean? "The legal basis for handling plant protection products is complete," says Daniela Büchel of the Crop Protection Department of the Canton of St. Gallen. With courses and consultations, the agricultural center Salez is trying to better train farmers to use such resources.

Where does the drain pipe lead?

"The most important places on farms, where farmers mix pesticides or clean syringes," explains Büchel. "We assume that watercourse pollution often starts there." Particularly in old farms, farmers often did not know that a manhole did not drive sewage into the manure pit, but directly into a stream. In such cases, the drainage system should be analyzed and new lines laid.

"Another possibility is that wastewater is collected and passed through a biofilter." Such solutions are part of the vast Pesticide action plan of the federal government, implemented since 2018. "Since many improvements require structural adjustments, it will take some time for the measures to take effect," Büchel said. The sustainable use of pesticides would also be achieved by other means. Among others with the use of weeding robots. Büchel says:

"It is important for us that you approach this complex subject holistically."

Ecologists are not satisfied

For Pro Natura Eastern Switzerland, the measures of the canton and the farmers' association go too far. "Awareness is not enough," said Christian Meienberger, CEO. "That's why we support the two popular initiatives underway on this issue – especially the Healthy Drinking Water Initiative." This requires that farmers using pesticides be denied access to direct payments.

"It is impossible for us to continue subsidizing the destruction of nature."

The other rivers of Mittelland are also very polluted.

Is the pollution of watercourses in the Canton of St. Gallen particularly dramatic? "The substances found in problematic concentrations in St. Gallen's watercourses are also found in other Swiss watercourses subjected to similar use," said Tobias Doppler of the University of St Gallen. 39, Swiss Association of Experts in Wastewater and Water Protection.

They are agricultural pesticides, but also industrial chemicals and drug residues. "Drug residues often escape from wastewater treatment plants to water courses," says Doppler. With the planned introduction of the fourth so-called purification step, these trace substances should be largely eliminated. However, these cleaning systems are not provided in all treatment plants. A direct link between chemicals in water courses and the quality of drinking water can not be established, says Doppler.

"The drinking water is finally taken from groundwater or lakes."

Brooks as an early warning system for groundwater

The soil holds many impurities when water infiltrates the surface into the groundwater. Some substances, however, remain in the water. "Groundwater has been monitored regularly in the Canton of St. Gallen for more than 20 years," said Markus Oberholzer, of the groundwater service of the Office of Water and Energy . In the current samples, we mainly find pesticides, which are now banned. Atrazine and its degradation products or the products of decomposition of dichlobenil, for example. Of the other substances, only very small amounts are found.

The results of the ongoing study on small coves in the township are not a cause for direct concern, says Oberholzer. "Much of the groundwater does not seep into the subsoil by small streams, but by larger waters." And their pollutant concentrations are significantly lower. However, surface water is an important early warning system for groundwater. "That's why we have to stay alert."