Analyses reveal significant impact of wastewater treatment plants on Sava River fish kill

A significant fish kill in the Sava River, stretching for dozens of kilometers downstream from Zagreb, has been linked to the discharges from wastewater treatment plants in Zagreb and Velika Gorica. Analyses conducted after the event revealed that pollutant concentrations at both discharge points exceeded permitted limits, according to reports from Jutarnji list.

The Institute of Water, which analyzed the water quality in relation to the mass fish death, estimated that the treatment plants' contribution to the situation was substantial, though not the sole cause. This contradicts earlier statements from Zagrebački Holding, which had claimed the Zagreb plant's output parameters were within legal limits.

In addition to the pollution from the treatment plants, the analyses also highlighted other unfavorable conditions in the river. Water temperatures were higher than the prescribed annual average, and dissolved oxygen levels were low. This combination of high temperature and low oxygen can severely impact fish populations and contribute to mortality.

Veterinary authorities have largely ruled out infectious fish diseases as the cause of the large-scale die-off, based on initial findings from the Croatian Veterinary Institute. Water management inspectorate proceedings are ongoing due to the confirmed exceedances of pollutant limits. Further tests are being conducted to fully understand the situation.