August 2021

Wastewater flowing through a river bed (Mexico).
Photo: Jan Siemens

The research group FOR 5095 “Interactions of pollutants, antibiotic resistance and pathogens in a changing sewage irrigation system” will examine the selection of antibiotic resistance and the spread of pathogens in agricultural systems and their transfer into food using the example of the world's largest sewage irrigation system north of Mexico City. The approximately 900 square kilometer area was irrigated with a mixture of untreated sewage and rainwater for about 100 years. As a result, drugs, disinfectants, metals and numerous other substances have accumulated in the soil in the fields. The world's third largest sewage treatment plant has now been put into operation in the Valle Mezquital, so the wastewater from Mexico City no longer reaches the fields untreated.

"Wastewater treatment plants are (...) a potential hotspot for the selection of antibiotic-resistant bacteria - the clarified water will contain fewer bacteria than before, but it may contain a larger proportion of multi-resistant bacteria," says Prof. Siemens, professor for Soil Resources and Soil Protection, and spokesman for the new DFG research group. "There is also a risk that pollutants that have accumulated in the soil in the past will be mobilized by the treated wastewater and increase the selection of antibiotic-resistant bacteria in the fields."

The professorship for Recycling Microbiology at the iFZ is also part of the research group, as are scientists from the University of Bonn, the University Hospital Bonn, the Beuth University of Applied Sciences in Berlin, the Julius Kühn Institute and the University of Tübingen. The project is carried out in cooperation with the Universidad Nacional Autónoma de México.

For more information:
Prof. Dr. Jan Siemens, Soil Science and Soil Conservation