As part of the fulfilment of the EU Water Framework Directive, phosphorus emissions from municipal wastewater treatment plants are to be further reduced, as these contribute to the fact that the good ecological status of surface waters has not yet been achieved. Metal salts (e.g. ferric chlorides, ferric chloride sulfates, aluminum sulfates, aluminum chlorides) are used as precipitants in the chemical-physical elimination of phosphorus in wastewater treatment plants, and an increase in the quantities of precipitants can be expected to lead to an increase in the salinity of treated wastewater and thus of the surface waters receiving the wastewater.

 The fact that salts can also represent an ecological problem in water bodies has not yet been considered. Although salts occur naturally in freshwater and vary in composition due to geological conditions (primary salinization), increases in salinity due to anthropogenic influences (secondary salinization) and especially changes in the ionic composition of water can harm freshwater organisms. In addition to wastewater discharges, other drivers contributing to secondary salinization of surface waters in Germany include mining, the use of winter road salt, and agriculture.

The project will investigate to what extent emissions from wastewater treatment plants contribute to the salinization of water bodies and what role phosphorus elimination by chemical precipitation plays in this process. In addition, the effects of increased salt concentrations on aquatic biocoenoses will be investigated.

Duration: January 2022 - June 2023

Collaborators: Collaboration between iES Institute for Environmental Sciences and Institute Water Infrastructure Ressources, RPTU Kaiserslautern-Landau.

• M.Sc. Theresa Piana, RPTU Kaiserslautern-Landau
• Jun.-Prof. Dr. Elisabeth Berger, RPTU Kaiserslautern-Landau
• Dipl.-Biol. Birgit Valerius, RPTU Kaiserslautern-Landau
• Dr.-Ing. Henning Knerr, RPTU Kaiserslautern-Landau

Funding: Carl Zeiss-Stiftung