- At the Werdhölzli sewage treatment plant in Zurich, incompletely treated wastewater escaped into the Limmat early on Sunday morning.
- The Stapo advises not to swim, bathe or swim below the Werdinsel to the Dietikon power plant.
- The cause of the leak was a power outage shortly before 3 a.m., which briefly interrupted cleaning in the Werdhölzli ARA.
In Zurich, contaminated wastewater has leaked into the Limmat – now the Zurich city police are warning people to avoid a certain part of the river. Early on Sunday morning, incompletely treated wastewater escaped into the Limmat at the Werdhölzli wastewater treatment plant (WWTP). “For this reason, it is not recommended to swim, bathe or swim below the Werdinsel in the Limmat,” says the Stapo.
Contaminated water in Limmat
According to initial findings, shortly before 3 a.m. due to a power outage, there was a brief leak of only pre-cleaned water from the Werdhölzli sewage treatment plant. This still contaminated water then flowed into the Limmat.
“Because contamination of the water cannot currently be ruled out, it is not recommended to bathe, swim or go out on the water by boat below the Werdinsel to the Dietikon power plant in the Limmat on Sunday, June 28, 2026,” warns the Stapo in its statement.
Cleaning was restricted for 75 minutes
“The complete cleaning was interrupted from 3 a.m. to 4:15 a.m.,” says Tobias Nussbaum, ERZ media spokesman. Since then, full cleaning performance has been guaranteed again. For 75 minutes, only the mechanical cleaning, i.e. the sieve that held back the visible dirt, worked on the system. The finer cleaning stages, which retain bacteria and invisible dirt, did not work.
It is difficult to assess what health risks there are. One thing is certain: “There are health risks only if the water is drunk intentionally or unintentionally – such as symptoms such as nausea, fever, vomiting, abdominal cramps or diarrhea.” What exactly is in the water is currently being investigated and is still unclear. “The wastewater has a different composition,” says Nussbaum. The current also constantly mixes it.
One thing is certain: “We currently advise against entering the water in the affected area. This is a measure that we have taken as a precaution.”
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Benedikt Hollenstein (bho) has been at 20 minutes since 2021. He writes for the news desk and also takes on day management shifts there.
