Department Process Engineering

The Eawag Aerobic Granular Sludge (AGS) Model

The Eawag AGS model has been developed at Eawag within the Aerobic Granular Sludge project and implemented in Sumo© (Dynamita). The model consists of (1) a bioreactor model (Eawag AGS reactor model), (2) a biofilm model (adapted SumoBioFilm) and (3) a biokinetic model (free choice among the available Sumo© models).

The key features of the Eawag AGS reactor model are:

  1. Operation as sequencing batch reactor (SBR).
  2. Constant volume operation / simultaneous fill-draw SBR achieved by plug-flow feeding through an in-series assembly of 4 completely stirred tank reactors (CSTR, called child units). Improved quality of plug-flow hydrodynamics by rule-based programming.
  3. Individual settling models for granules (discrete particle settling) and flocs (flocculated, hindered and compressed settling).
  4. Selective excess sludge removal either based on target solid retention time (SRT) or fixed volume wastage after a certain time and at a reactor heigth.
  5. Prediction of sludge bed stratification, effluent total suspended solids and washout dynamics.

Figure 1: The Eawag AGS Parent unit (left) is assembled of 4 Eawag AGS Child units and several internal / external connecting pipes (right).

The key features of the biofilm model are:

  1. Bulk and biofilm (granule) compartments.
  2. 1D biofilm model.
  3. Granules are modelled as spheres with fixed biofilm thickness composed of n layers. All granules in the reactor have the same diameter. Both the granule granule radius (=biofilm thickness) and the number of layers are user inputs.
  4. The initial volume and number of granules within the system are user inputs. Granules cannot grow in size, but in density (up to a maximum).
  5. The mass-transfer mechanisms in the biofilm model are:
  • Diffusion of soluble and colloidal compounds between all compartments (bulk - granule surface and between all granule layers).
  • Displacement of particulate compounds.
  • Internal transfer of particulate compounds between the granule layers.
  • Attachment of particulate compounds from the bulk to the granule surface layer.
Figure 2: Conceptual representation of the biofilm model

The "Eawag AGS model package" can be downloaded here and contains:

  1. Eawag AGS Model files: Eawag AGS parent unit, child unit, influent, effluent, sludge and side-flow combiner units for use in Sumo©.
  2. User manual.
  3. Sumo© project examples: run-ready Sumo© projects listed in the user manual.
  4. Data extraction files: for simple data extraction from your Sumo© simulation runs.
  5. R tool: R-script for basic analysis and plots
  6. Python runner: for scheduling and performing multiple (parallel) Sumo© simulation runs


Support via Email: please contact Dr. Nicolas Derlon


Manuel Layer, Phd thesis

M. Layer, A. Brison, M. Garcia Villodres, M. Stähle, F. Házi, I. Takács, E. Morgenroth and N. Derlon 2021. Modelling of microbial particulate organic substrate conversion of aerobic granular sludge systems: limited anaerobic conversion and the essential role of flocs. Manuscript submitted for publication

N. Derlon, M. Layer, M. Garcia Villodres, A. Brison, M. Stähle, D. Bencsik, F. Házi, I. Takács and E. Morgenroth 2021. Modelling of granular sludge sequencing batch reactors: introduction of the Eawag AGS model. Manuscript in preparation

Results from the Eawag AGS model

Project lead

Dr. Nicolas DerlonTel. +41 58 765 5378Send Mail