How to handle hospital wastewater
Background
Micropollutants (e.g. pharmaceuticals) are increasingly detected in water bodies: their elimination in 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. Experts are currently discussing, whether hospitals
as important point sources could be the target of first 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 (www.novaquatis.ch/index_EN),
which contains ca. 60–70% of the medicals that are excreted by humans.
Several European countries are building first pilot plants to treat
hospital wastewater (www.pills.eu).
So far, the directly involved people are not systematically included in
the difficult decision on how to best proceed. This project focuses on
a relevant, well-defined decision situation with two Swiss case studies
that could be important point sources and thus target of first
measures: a cantonal hospital and a cantonal psychiatric clinic. As
approach we combine a ‘stakeholder analysis’ (also with H. Mosler) with ‘multi-criteria decision analysis’ (also with H. Siegrist, P. Reichert).
Stakeholder analysis
Stakeholder analysis was developed as response to many past failures of projects due to resistance by those involved. It is a powerful method for policy analysis and strategy formulation. We will identify key stakeholders with a set of expert interviews. We follow a conceptual framework to characterize the stance and attitude of stakeholders to the issue, and to identify their relationships as well as more general barriers and resources. The analysis will help to sort out the primary stakeholders and serves as basis for future stakeholder participation.
Multi-criteria decision analysis (MCDA)
MCDA is a methodology to structure difficult decision problems and elicit stakeholder preferences. The current state of knowledge and novel chemical, ecotoxicological, and engineering data (C. McArdell, B. Escher, H. Siegrist) will be compiled. The goals, preferences, and values of relevant stakeholders are obtained with interviews. The integration of (objective) scientific and (subjective) stakeholder data allows to rank different technical and organizational measures to treat hospital wastewater. The outcome helps to identify potential disagreements or consensus solutions. However, equally important are improved understanding and social learning for the participants. To this end, the final results will be discussed in a stakeholder forum, where the usefulness of the proposed procedure will also be tested. This can provide a valuable basis for future decision making concerning more general issues on how to deal with micropollutants.
Goals
- Compile and integrate existing data on technical and organizational options to reduce pharmaceuticals from wastewater streams
- Estimate the relevance and contribution of hospital point sources to the total pharmaceutical load in wastewater, based on two case studies
- Increase acceptance by systematically integrating the relevant stakeholders in the decision making process
- Provide suggestions on how to best proceed with the issue of pharmaceuticals in hospital wastewater (specifically for each case study and generally for Switzerland)
- Evaluate the usefulness of MCDA methodology for the stakeholders and gain empirical information on complicated decision processes involving multiple stakeholders with (presumably) diverging interests
Results
Conventional wastewater treatment plants (WWTP) do not eliminate all micropollutants; onsite treatment of hospital wastewater could decrease pharmaceutical emissions. Although there is no legal directive for hospital wastewater treatment (yet), some hospital directorates are concerned. We used Multiple-Criteria Decision Analysis (MCDA) to support a complex decision in two exemplary cantonal hospitals (general hospital Baden; psychiatric clinic Hard, Embrach).
Escher et al. (2011) evaluated the ecotoxicological potential of the 100 pharmaceuticals expected to occur in highest quantities in the hospitals’ wastewater. Toxicity data were related to predicted concentrations in different wastewater streams to assess the overall risk potential for different scenarios (conventional biological pretreatment in hospital; urine separation). The general hospital contributed ca. 38% to the total pharmaceutical load at the WWTP, the psychiatric clinic 5%. The lists of Top-100 pharmaceuticals were distinctly different between the two hospitals with only 37 pharmaceuticals overlapping in both datasets. 31 Pharmaceuticals in the general and 42 in the psychiatric hospital thus were predicted to contribute to the risk posed by the emitted mixture of pharmaceuticals. However, together they constituted only 14% (hospital) and 30% (psychiatry) of the pharmaceutical load. Hence, medical consumption data alone are insufficient predictors of environmental risk. The environmental risk was dominated by amiodarone, ritonavir, clotrimazole, and diclofenac. Only diclofenac is well researched in ecotoxicology. The computational analysis thus helps setting priorities for further toxicity testing.
A stakeholder analysis identified who is affected by this decision or should take action (Lienert & Mosler, in prep.). Because of uncertain cause-effect relationships, authorities are crucial. In this interview-series with 20 stakeholders (authorities, hospital-internal actors, wastewater experts), we identified four fundamental main objectives: low costs, good wastewater quality, good feasibility, and good public perception.
We then analyzed 68 and 50 technical and organizational alternatives, respectively, for the general and psychiatric hospital to reduce pharmaceutical discharge, including reverse osmosis, ozonation, activated carbon, and urine separation (Lienert et al., 2011; Schuwirth et al., subm.). Using MCDA, we combined expert predictions (e.g., costs, ecotoxicological risk, pharmaceutical mass flows, pathogen removal) with subjective preference-valuations from 26 stakeholders.
We modified standard methods to elicit weights by introducing a ‘Reversed-Swing Method’ that we found more realistic (Schuwirth et al., subm.). We set up a procedure that compromises between time demand and elaborateness, but remains methodologically satisfactory, and did a sensitivity analysis. We also found that initial agreement of stakeholders on objectives and a careful choice of attributes and boundary conditions are crucial.
MCDA revealed that for the general hospital alternatives removing all pharmaceuticals (especially reverse osmosis, or vacuum-toilets and incineration) performed systematically better than the status quo or urine separation, despite higher costs (Lienert et al., 2011). They now require closer scrutiny. To remove X-ray contrast agents, introducing roadbags is promising. For the psychiatry with a lower pharmaceutical load, costs were more critical. Stakeholder feedback concerning MCDA was very positive, especially because the results were robust across different stakeholder-types.
Publications
- Escher, B.I., R. Baumgartner, M. Koller, K. Treyer, J. Lienert, C.S. McArdell (2011) Environmental toxicology and risk assessment of pharmaceuticals from hospital wastewater. Water Research 45(1): 75–92.
- Lienert, J., M. Koller, J. Konrad, C.S. McArdell, N. Schuwirth (2011) Multiple-criteria decision analysis reveals high stakeholder preference to remove pharmaceuticals from hospital wastewater. Environmental Science & Technology 45(9): 3848–3857.
- McArdell C.S., J. Lienert (2011) How to deal with hospital wastewater? Eawag Annual Report 2010: pp. 10–11. Download: http://www.eawag.ch/medien/publ/jb/2010/jb10e.pdf
- Schuwirth, N., P. Reichert, J. Lienert (2012) Methodological aspects of multi-criteria decision analysis for policy support: A case study on pharmaceutical removal from hospital wastewater. European Journal of Operational Research 220: 472–483.