Micropollutants (e.g. pharmaceuticals) are increasingly detected in water bodies: their elimination in conventional wastewater treatment plants (WWTP) is incomplete. Mostly, we are facing considerable uncertainty about aquatic ecosystem effects, with some exceptions. For instance, negative effects on fish reproduction have been linked to the exposure of estrogens (female hormones). In such a complex decision situation with high uncertainty and many stakeholders involved, decisions cannot be made by scientists alone, but participatory and multidisciplinary approaches are needed. For instance, technologies to eliminate micropollutants at WWTP are expensive, and society will have to decide, whether potential risks justify the high costs.
Micropollutants can be reduced by new technologies at WWTP or source control. Hospitals that are important point sources could be one target of measures. Options include treating all hospital wastewater or partial treatment (e.g. oncology wards to remove cytostatics (anti-cancer drugs)). Moreover, only the urine could be collected and treated separately, since the urine contains ca. 60–70% of the medicals that are excreted by humans. Urine source separation has been intensively researched in the project Novaquatis. At European level, the reduction of pharmaceutical residues from wastewater has been researched in the projects PILLS and noPILLS.
This project focused on a relevant, well-defined decision situation with two exemplary Swiss case studies: a cantonal hospital and a cantonal psychiatric clinic. MCDA was used to combine expert predictions (e.g., costs, pharmaceutical mass flows, ecotoxicological risk, pathogen removal) with the subjective preferences of 26 stakeholders. The example also served to study more general research questions related to the practical application of MCDA in environmental decision problems.