The Role of Calibration and Validation in Wastewater Modelling

The workshop is organised by the IWA Task Group on Good Modelling Practice – Guidelines for Use of Activated Sludge Models (GMP).

Chair: Leiv Rieger, EnviroSim Associates Ltd., Hamilton, Canada,

When: Monday, 20 June 2010, 11:00-15:00

Where: San Sebastian (TECNUN). Room 1.

Registration: not necessary, entrance free


Mathematical modelling of activated sludge systems is used widely for plant design, optimisation, training, research and model-supported process controller design. The quality of simulation studies can vary strongly depending on the project objectives, resources spent and expertise available. Consideration has to be given to the model accuracy and the amount of time necessary to produce the required accuracy.

In the proposed workshop, two key aspects for model prediction accuracy will be discussed:

  • Calibration
  • Validation

A variety of definitions for calibration exists and the strictest definition might call many of the parameter changes “fiddling” rather than real calibration. It is difficult for a modeller to find the “right” procedures for model calibration. Whereas fully automated estimation of all model parameters is discussed in academia, there is hardly any application of these sophisticated methods in engineering practice. The question arises whether this is due to a lack of understanding or whether experienced-based methods deliver better and more reliable results. The answer is that there is probably a lack of communication between academia and practitioners and the proposed workshop will bring together experts from both sides to discuss proper calibration strategies.

Validation is essential in hydrological modelling and requested in most wastewater treatment modelling guidelines. However, what is the role of validation in mechanistic wastewater treatment models? Is one validation enough? What conditions should be validated? What happens if the validation fails? Can the model be used without validation and what is the uncertainty of using an un-validated model versus one that has been validated? Is there sufficient and adequate data with which to carry out a validation? These questions will be brought up in the workshop discussions.


The IWA TG on Good Modelling Practice collected international experience in the field of wastewater treatment modelling through expert groups, interviews, workshops, questionnaires, publications and modelling courses. The GMP task group is currently finalizing an IWA Scientific and Technical Report (STR), which will summarize international experience and knowledge and is defining good modelling practice for activated sludge systems. The workshop is supported by the IWA TG on Design and Operations Uncertainty (DOUTGroup).


Leiv Rieger (chair GMP task group), EnviroSim Associates Ltd., Canada

Dirk Muschalla (secretary RTCUDS), ITWH, Germany

Marc Neumann (DOUTGroup), Université Laval, Canada

Imre Takács (GMP task group),  Dynamita, France

Lorenzo Benedetti (secretary DOUTGroup), WATERWAYS S.R.L., Italy

Sylvie Gillot (GMP task group), Cemagref, France


Consultants, Plant managers or operators, waterboards and academics interested in modelling wastewater treatment plants. The GMP TG has been organizing a whole series of workshops with a proven track record of good attendance and excellent evaluations. Watermatex 2011 was chosen for this workshop because of the right mixture of experts with backgrounds in system analysis and practical engineering.

Expected Outcomes

Fruitful discussions amongst modelling experts from a variety of backgrounds should lead to more precise definitions of these two key aspects for model prediction accuracy. It is planned to write and publish a white paper on calibration and validation in mechanistic wastewater treatment modelling.


Workshop on
The Role of Calibration and Validation in Wastewater Treatment Modelling
Time Topic Type Speaker / Moderator
11:00 - 11:15 Welcome Leiv Rieger
11:15 - 11:30 Methods for parameter estimation Discussion starter Marc Neumann
11:30 - 11:45 Experience-based calibration Discussion starter Imre Takács
11:45 - 12:00 Calibration and validation in hydrological modelling Discussion starter Dirk Muschalla
12:00 - 12:15 The role of validation in mechanistic modelling Discussion starter Lorenzo Benedetti
12:15 - 12:30 Validation in wastewater treatment modelling practice Discussion starter Sylvie Gillot
12:30 - 14:00 Lunch break
14:00 - 14:10 Summary of discussion starters Leiv Rieger
14:10 - 14:50 Group discussion Moderated discussion
14:50 - 15:00 Wrap up of workshop

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