This page provides additional material to complement Guidelines for Using Activated Sludge Models (part of the Scientific and Technical Report series) by the IWA Task Group on Good Modelling Practice. These resources are designed to assist Good Modelling Practice (GMP) in activated sludge modelling and include case studies, spreadsheets with error-checked Gujer Matrices and various modelling tools in spreadsheet format.

Download additional reference materials for this book using the links below.

Guidelines for Using Activated Sludge Models

Leiv Rieger, Sylvie Gillot, Günter Langergraber, Takayuki Ohtsuki, Andrew Shaw, Imre Tak´cs, StefanWinkler

September 2012, ISBN 9781843391746

IWA Task Group on Good Modelling Practice: 
Leiv Rieger (chair), Sylvie Gillot, Günter Langergraber, Takayuki Ohtsuki, Andy Shaw, Imre Takács, Stefan Winkler

Mathematical modelling of activated sludge systems is used widely for plant design, optimisation, training, controller design and research. The quality of simulation studies varies depending on the project objectives, finances and expertise available. Consideration has to be given to the model accuracy and the amount of time required carrying out a simulation study to produce the desired accuracy. Inconsistent approaches and insufficient documentation make quality assessment and comparison of simulation results difficult or almost impossible. A general framework for the application of activated sludge models is needed in order to overcome these obstacles.

The genesis of the Good Modelling Practice (GMP) Task Group lies in a workshop held at the 4th IWA World Water Congress in Marrakech, Morocco where members of research groups active in wastewater treatment modelling came together to develop plans to synthesize the best practices of modellers from all over the world. The most cited protocols were included in the work, amongst others from: Hochschulgruppe, STOWA, BIOMATH and WERF.

The goal of the group was to set up an internationally accepted framework to deal with activated sludge models in practice. This framework shall make modelling more straightforward and systematic especially for consultants and other practitioners. Additionally, it will help to define quality levels for simulation results, a procedure to assess this quality and to assist in the proper use of the models. The goals can be summarised as follows:

  • Set-up of an internationally accepted framework for activated sludge modelling, with a strong emphasis on the quality control of simulation studies.
  • The framework should be targeted towards practitioners and consultants and therefore cost aspects are very important.
  • Identify and classify different model application goals together with the appropriate effort to obtain results with sufficient quality to meet the objectives of the study.

The GMP Task Group hopes to achieve these objectives through the publication of a Scientific and Technical Report entitled Guidelines for Using Activated Sludge Models.

The GMP Task Group has developed a Unified Protocol and an Application Matrix as the basis for the modelling framework. The Unified Protocol was developed by synergizing the best salient features of several published modelling protocols and consists of five major steps:

  1.     Project definition
  2.     Data collection and reconciliation
  3.     Plant model set-up
  4.     Calibration and validation
  5.     Simulation and result interpretation

The Application Matrix consists of a list of 14 typical modelling applications and indicates the relative rigour with which each of the Unified Protocol steps should be carried out for the particular application.

Additional features in the STR include a chapter on modelling industrial wastewater, an overview on the history, current practice and future of activated sludge modelling and several explanatory case studies. It can be used as an introductory book to learn about Good Modelling Practice (GMP) in activated sludge modelling and will be of special interest for process engineers who have no prior knowledge of modelling or for lecturers who need a textbook for their students. The STR can also be used as a modelling reference book and includes an extended appendix with additional information and details of methodologies.

Additional reference materials available to download here:

Good Modelling Practice Application Matrix

A systematic approach for model verification – Application on seven published Activated Sludge Models 

Spreadsheet to calculate # of tanks in series according to tank geometry, flow and aeration

Excel Workbook for the Generation of diurnal variation for influent data for dynamic simulation


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