Each year, around 130 kilograms of mercury flow into Swiss wastewater treatment plants, which filter out the lion’s share from the waste water. This is shown by a survey of almost thirty wastewater treatment plants conducted by the Swiss Federal Institute of Aquatic Science and Technology (Eawag) and the Federal Office for the Environment (FOEN).
Europe still has barely any downstream passage facilities that guide fish past the turbines of run-of-river power stations unharmed. Now, an interdisciplinary team of engineers from ETH Zurich and fish biologists from Eawag have developed a rack that uses pressure and flow differences to guide fish out of the main flow and into the safe fish passage. Laboratory tests have shown that the system, which works by influencing fish behaviour, is particularly effective for cyprinid fish and salmon parr.