What is the best way to replace an old wastewater treatment plant? Which early warning system is most successful in protecting against flooding? Thanks to a method developed by Eawag, experts can analyse complex decision-making problems in a simple way.
“ValueDecisions” is the name of the new tool developed by Judit Lienert and her research group, which deals with decision analysis at the aquatic research institute Eawag. The web app relieves users of the complicated programming work that was previously required for professional decision-making. “We use a method called ‘multi-criteria decision analysis’,” explains Lienert: “In principle, this is a cost-benefit analysis; however, it is not only about the lowest possible costs, but also a wide range of other objectives, and the decisions involve many stakeholders with conflicting interests, so a good choice cannot be made with common sense alone.” In technical jargon, the method is called MCDA, short for “Multi-Criteria Decision Analysis”.
The ValueDecisions app calculates and visualises the results of the MCDA in clear graphical representations and tables. “You can see at a glance which options are best for the stakeholders and where a compromise is possible,” says the environmental social scientist and biologist. While a script with complex programming runs in the background, the interface is very user-friendly. All you have to do is upload two Excel spreadsheets. “However, you should have an idea of problem structuring and MCDA to collect the necessary data for these two tables,” explains the researcher.
This is why ValueDecisions is aimed primarily at professionals, for example, in engineering offices, at municipalities or in research, and not the general public. “But, of course, you can also feed the app with personal decision-making problems,” says Lienert, “for instance, if you want to find the optimal destination for a family holiday.” This allows you to explore which of the many vacation possibilities best suits the wishes of each individual family member, and which is the best compromise.
Wastewater treatment in Paris
ValueDecisions has already proven itself several times in research practice. For example, Lienert’s group investigated how wastewater in the Paris region could best be treated in the future. The existing, large wastewater treatment plant is reaching its capacity limits because the population is constantly growing and climate change will lead to reduced dilution of the treated wastewater in receiving rivers. “We were asked whether alternative wastewater treatment systems could be considered,” says Lienert. In a workshop with local experts, both environmental as well as socio-economic objectives were established and subsequently five options were selected, including decentralised options with urine and faeces separation and dry toilets. This selection formed the basis for a survey of 655 people from the region who were able to indicate their wishes and preferences.
Graph by ValueDecisions on five different options for wastewater disposal in Paris (x-axis). How well each sub-objective is achieved is indicated with coloured blocks (A_ Environmental protection, B_ Resource use, C_ Social well-being, D_ Economic performance). Depending on the environmental attitude (preservationists or utilitarians), the options achieve the sub-objectives and the overall objective to different degrees (values from 0 - 1 on the y-axis). However, the status quo, the conventional wastewater treatment plant, always performs significantly worse than a decentralised vacuum system with urine source separation and dry toilets with underground compost chambers on site.