Science communication


A revised Urban Wastewater Treatment Directive needs to address the chemical flow in modern society

When the Commission revises the Urban Wastewater Treatment Directive, UWWTD, the directive needs to be seen as part of the solution to decrease the chemical load of micropollutants in our fresh and marine waters, writes the Baltic Sea Centre in its reply to the European Commission’s consultation on the roadmap for a revision of the UWWTD.

Text: Hanna Sjölund

The current directive is from 1992 and a lot has happened since then. For instance the Water Framework Directive and the Marine Strategy Framework Directive are both from the first decade of the 21st century. The awareness of the increased flow of and effects from micropollutants, such as chemicals and pharmaceuticals has since risen dramatically. These aspects need to be aligned in order to ensure a safe aquatic environment.

In the Commission’s consultation on the roadmap, which closed today, the Baltic Sea Centre points out that UWWTPs can be important entry routes for some priority substances and river basin specific pollutants and therefore requirements on wastewater quality with respect to micropollutants need to be introduced. Assessments of wastewater and sludge that go beyond the single chemical approach can be used to identify substances of emerging concern, as currently discussed under the WFD and MSFD.

The Baltic Sea Centre also stressed that upstream measures to reduce the chemical load must remain key overall. However, UWWTPs are one of few collection points for chemical flows in our society, which provides an opportunity to remove a broad range of chemicals emitted from human activities from the water cycle by employing more advanced treatment techniques targeting micropollutants. By imposing chemical quality limit values on outgoing water from UWWTPs in the larger agglomerations, total emissions of known and unknown substances and associated risks to the aquatic system could be significantly decreased.

According to research at the Baltic Sea Centre, out of the ca 615 UWWTPs closest to the Baltic Sea coast, about 45 plants receive wastewater from more than 100 000 p.e. and together treat almost 70% of the wastewater from the coastal population. Currently employed advanced treatment technologies have, with reasonable operating conditions, an average micropollutant removal efficiency of ca 70-80%. Upgrading the largest UWWTPs would hence reduce the total load from all coastal UWWTPs by approximately 50%. Introducing requirements on micropollutant treatment for at least the larger UWWTPs in the UWWD therefore has the potential to significantly lower concentrations of a wide range of micropollutants in seawater. This is particularly important for persistent and water soluble chemicals since they easily escape conventional UWWTPs, spread in waterways and accumulate in aquatic “end-stations” such as the Baltic Sea.

Read the Baltic Sea Centre's full comment on the European Commission's inception impact assessment of the Urban Waste Water Treatment Directive here.