Developing a model based decision support tool for the identification of sustainable treatment options for domestic wastewater A.J. Balkema*, H.A. Preisig*, R. Otterpohl**, A.J.D. Lambert and S.R. Weijers* *Systems and Control Group, Faculty of Applied Physics, Eindhoven University of Technology, P.O.Box 513, 5600 MB Eindhoven, The Netherlands (E-mail: A.J.Balkema@tue.nl) **Technical University Hamburg-Harburg, Institute of Municipal and Industrial Wastewater Management, Eissendorfer Str.42, D-21073 Hamburg, Germany Abstract To enable decision makers to select sustainable wastewater treatment systems, insight into the sustainability of a wide variety of systems should be provided in a transparent way leaving room for adaptation and interpretation according to the local situation. To provide this insight a structured methodology comparing wastewater treatment systems with respect to sustainability is defined. Similar to life cycle assessment (LCA) three phases can be distinguished: (1) goal and scope definition, (2) inventory analysis, and (3) optimisation and results. In the goal and scope definition we set the system boundaries to include most of the water cycle and part of the food cycle. Furthermore, we defined a multi-disciplinary set of sustainability indicators including technical, economic, environmental, and socio-cultural aspects. In the inventory analysis these sustainability indicators are quantified using simple static models of wastewater unit operations. Selection of unit operations results in a model of a complete wastewater treatment system. In the optimisation phase the decision maker can weigh the different sustainability indicators and select sustainable options through integer programming. Keywords Decision support; domestic water system; modelling; sustainability assessment; wastewater treatment Introduction Sustainability challenges us to look at wastewater treatment systems from a different angle. New perspectives are opened when assessing the domestic water system as a whole, includ- ing most of the water cycle (water supply, use, and treatment) and part of the food cycle (including bio-waste, and recycling of nutrients to agriculture). This enables the compari- son of integrated solutions comprising water reuse, recycling, alternative treatments such as urine separation, etc. A system analysis approach, in which one chooses from a wide variety of unit operations thus suggesting new combinations and exposing new ideas, should provide insight into the sustainability of alternative domestic water systems. For this purpose, we are developing a model based decision support tool that enables the com- parison of a wide variety of systems using a multi-disciplinary set of sustainability indica- tors. This paper describes the goal and scope of our research (setting the system boundaries and selecting the sustainability indicators), the outlines of the inventory analysis (defining the superstructure that forms the modelling framework) and the optimisation (integer pro- gramming using the weighted sum of the sustainability indicators as objective function). This is preceded by a review on comparisons of wastewater treatment systems with respect to sustainability. Comparing wastewater treatment technologies: a review Several researchers describe a comparison of wastewater treatments systems (Bengtsson et al., 1997; Emmerson et al.; 1995, Hellström, 1997; Lundin et al., 1999; Mels et al., 1999; Water Science and Technology Vol 43 No 7 pp 265–269 © 2001 IWA Publishing and the authors 265 Downloaded from http://iwaponline.com/wst/article-pdf/43/7/265/429887/265.pdf by guest on 13 December 2023