Policy Brief: Limiting sulphate load of wastewaters calls for environmental quality standards

New ways of producing and storing energy are necessary in order to mitigate climate change. To achieve this, mining and battery technology industries are also needed in Finland. Particular concerns have been raised recently over large sulphate discharges of wastewaters into water bodies. “New studies have shown that sulphate can harm organisms, especially in lakes,” says Jouni Lehtoranta, Senior Researcher at the Finnish Environment Institute. This issue is also topical because a revision of the Government Decree on Substances Dangerous and Harmful to the Aquatic Environment is about to be launched.

Sulphate is harmful to lake organisms

The concentration of sulphate that is harmless to organisms has been studied by the University of Jyväskylä and the Finnish Environment Institute. “Toxicity tests indicate that a high load may have adverse effects on aquatic organisms, especially in lakes with naturally low sulphate concentration. In the Baltic sea, organisms adapted to salinity appear to tolerate much higher sulphate concentrations than those in lakes,” says Matti Leppänen, Senior Researcher at the Finnish Environment Institute.

Both short-term and long-term sulphate exposure tests were carried out on organisms in inland waterways and the brackish water of the Baltic Sea. The safe sulphate concentration in long-term exposure in freshwaters varied between 39 and 65 milligrams per litre. In short-term exposure, the concentration varied between 257 and 339 milligrams per litre. “We are still working on safe concentrations for brackish water species, but the harmless concentration seems to be significantly higher than in lakes,” says Leppänen.

Finnish Environment Institute proposes limit values

Sulphate is not currently classified as a harmful substance, and it is not included in the Finnish Decree on Substances Dangerous and Harmful to the Aquatic Environment. "Sulphate should be added to the Decree, and scientifically derived environmental quality standards should be set for it," says Jukka Mehtonen, Senior Coordinator at the Finnish Environment Institute.

Separate standards are needed for inland and coastal waters. The Finnish Environment Institute’s proposal for the quality standard of annual average concentration is 39 milligrams per litre for inland waters and 279 milligrams per litre for instantaneous concentration. As the studies are completed, environmental quality standards for sulphate will also be proposed for coastal waters.

“The harmful effects of sulphate can be mitigated by placing the wastewater discharge site in an area where the wastewater will dilute rapidly, and the dilute wastewater flows downstream or into the open sea. The most suitable discharge site can be found by modelling. Options for removing sulphate during manufacturing processes should also be investigated,” says Jouni Lehtoranta.

Mining and battery technology industries are essential in the green transition. However, the publication stresses that in green transition projects, it is also important to examine the overall environmental impacts, including on air, soil and water, as well as the life cycle impacts of manufacturing.

Finnish Environment Institute’s Policy Brief: Limiting sulphate load of wastewaters calls for environmental quality standards 

Further information

Jouni Lehtoranta, Senior Researcher, Finnish Environment Institute Syke, tel. +358 295 251 363, firstname.lastname@syke.fi

Matti Leppänen, Senior Researcher (studies on harmful effects of sulphates), Finnish Environment Institute Syke, tel. +368 295 251 368, firstname.lastname@syke.fi

Jukka Mehtonen, Senior Coordinator (Decree on Substances Dangerous and Harmful to the Aquatic Environment), Finnish Environment Institute Syke, tel. +358 295 251 421, firstname.lastname@syke.fi

Antti Belinskij, Research Professor (Environmental Law), Finnish Environment Institute Syke, +358 295 251 088, firstname.lastname@syke.fi

All Syke Policy Briefs:

www.syke.fi/policybriefs/en