Meta-tools: Helping engineers select adequate modelling methods

Peter Vanrolleghem

MSc in Bio-engineering (1987), with PhD in Applied Biological Sciences – Environmental Technology (1994), both from Ghent University (Belgium). His PhD dealt with monitoring, modelling and control of activated sludge processes, with special emphasis on model calibration and experimental design. He was associate professor at Ghent University since 1997, initiating the BIOMATH research team that by 2006 had grown to 25 researchers focusing on modeling methodologies for bioprocesses, mainly in environmental systems. Since 2006 he holds the Canada Research Chair on Water Quality Modeling, allowing him to start up the modelEAU research group at Université Laval in Quebec City (Canada). This group focuses on modeling, monitoring and control of water systems. modelEAU is quickly building momentum with now 2 research assistants, 3 post-docs, 10 PhD students and 5 Master students. These large research teams have helped him develop his publication record of over 300 peer reviewed papers. He is very active within IWA (IWA Fellow, member of IWA’s Strategic Council, chairman of the Specialist Group on Systems Analysis and Integrated Assessment, and member of a number of Task Groups) and is getting increasingly involved in WEF, where he was recently elected vice-chair of MEGA, the Modelling Expert Group of the Americas.

Meta-tools: Helping engineers select adequate modelling methods

Peter A. Vanrolleghem
modelEAU, Département de génie civil et de génie des eaux, Université Laval, 1065 av. de la Médecine, Québec (QC), G1V 0A6, Canada (Peter.Vanrolleghem@gci.ulaval.ca)

Abstract
When one evaluates recent modelling methodology focused publications that are related to water systems, it is striking to note that many of these publications do not deal with the presentation of innovative methods, but rather contribute by interesting comparisons of methods. It is hypothesized that the water industry searches for help in choosing the right method to use in a modelling project, rather than needs efforts to develop new methods that solve certain model-methodological problems. This seems a situation very similar to the one provokingly addressed by Willi Gujer in his Leading Edge Technology contribution in 2005 in Sapporo Japan where he called for a moratorium on activated sludge model development (Gujer 2006).

Rather than suggesting a moratorium, this paper calls for R&D efforts to create tools about modelling tools, i.e. meta-tools, that help the modeller pick up the right method among the large variety of methods he can choose among. Indeed, the modeller may not have the background, training or experience to make a proper judgement about the pro’s and con’s of individual methods and may stick to the default methods provided by the modelling software he/she is using.

The paper is not intending to present (the development of) such meta-tools, but wants to illustrate that in recent years quite some material has been collected that would allow the creation of a number of such meta-tools. The author has been involved in a number of such comparative studies that could form the basis for creating a meta-tool about, including:

1) Control strategy development (Ulf Jeppsson, this conference: “Quo vadis benchmark simulation models?”, work of the BSM Task Group)
2) Life cycle assessment (Lluis Corominas, this conference: “Towards a standard method for life cycle assessments (LCA) of wastewater treatment”)
3) Numerical solvers for ODE models (work of Claeys et al., 2010)
4) Optimization methods (an early comparison: Vanrolleghem & Keesman, 1996)
5) Process Monitoring methods (see the work of the BSM Task Group, among others)
6) Quality evaluation of models (Sylvie Gillot, this conference: “Towards quantitative quality criteria to evaluate simulation results in wastewater treatment”)
7) Sensitivity analysis methods (Giorgio Mannina, this conference: “Global sensitivity analysis in ASM applications: comparison of different methods”)
8) Uncertainty analysis methods (Peter Vanrolleghem, this conference: “Uncertainties in water system models – breaking down the water discipline silos”, work of the DOUT Task Group)
9) Verification of model implementation (Copp et al., 2008; Hauduc et al., 2010)
It is hoped that this contribution to Watermatex2011 may incite further research into method comparison and the development of meta-tools that will support the modeller with his/her selection among the increasing number of advanced modelling methods.

ACKNOWLEDGEMENT
Peter Vanrolleghem holds the Canada Research Chair in Water Quality Modelling

REFERENCES
Claeys P., van Griensven A., Benedetti L., De Baets B. and Vanrolleghem P.A. (2010) On numerical solver selection and related uncertainty terminology. J. Hydroinformatics, 12, 241-250.
Copp J.B., Jeppsson U. and Vanrolleghem P.A. (2008) The benchmark simulation models – A valuable collection of modelling tools. In: Proceedings International Congress on Environmental Modelling and Software (iEMSs2008). Barcelona, Spain, July 7-10 2008. Vol. 2, 1314-1321.
Gujer W. (2006) Activated sludge modelling: past, present and future. Wat. Sci. Tech., 53(3), 111-119.
Hauduc H., Rieger L., Takács I., Héduit A., Vanrolleghem P.A. and Gillot S. (2010) A systematic approach for model verification: Application on seven published activated sludge models. Wat. Sci. Tech., 61(4), 825-839.
Vanrolleghem P.A. and Keesman K.J. (1996) Identification of biodegradation models under model and data uncertainty. Wat. Sci. Tech., 33(2), 91-105.

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