The simulation system SIMBA# allows the holistic consideration of sewer system, wastewater treatment plant, sludge treatment and rivers. This new version SIMBA# is a stand alone simulation software and replaces the previous SIMBA 6.6 which was based on the basis software Matlab®/SIMULINK™ by MathWorks Inc.. All components necessary for a thorough analysis of the constituent subsystems, including their interactions, are now available within the same simulator. SIMBA# can be applied for a large variety of tasks in engineering practice and in research and education. This ranges from plant and process design to analysis and operational optimisation of operation of urban wastewater systems. 

SIMBA# is programmed in C# and it runs under the Windows 7, 8 and 10 operating systems.

Application areas

SIMBA# facilitates applications in engineering practice and in research and education:

  • Planning and design of WWTPs, considering operational variants including control
  • Optimisation of process design and operation of existing WWTPs
  • Analysis of process water management, sludge treatment and energy consumption
  • Analysis of flows in urban areas
  • Development and test of strategies for real time control of urban drainage systems
  • Analysis of interactions of runoff, wastewater treatment and receiving water quality
  • Analysis of process water treatment, sludge treatment and energy consumption

Model libraries

The setting up of simulation models is based on the graphically linking of model blocks- these blocks represent unit processes (e.g. sewer section, primary treatment, activated sludge tanks). SIMBA´s block library is the starting point for each simulation project. It contains blocks for the definition of wastewater and sludge flows. Additional blocks allow you to split and combine wastewater flows and also include sedimentation tanks and various reactor models (continously stirred tank reactors, plug-flow reactors) in order to allow the simulation of any arbitrary chemical and biological treatment process.

  • Activated Sludge processes for wastewater treatment (ASM1, ASM3, ASM3biop)
  • Biofilm processes of wastewater treatment (fixed-bed)
  • Anaerobic digestion processes, sludge treatment
  • Wastewater transport, storage and conversion processes in sewer systems
  • Water transport and quality in natural receiving waters
  • Control functions
  • Animated visualisation of simulation results

Simulation of wastewater treatment plants

For the simulation of WWTPs, a wide choice of transport/reactor models and activated sludge models is available. Transport/reactor models include, among others, model blocks for the description of activated sludge in tanks with intensive mixing and/or aeration by surface and pressurised aeration systems and primary and secondary clarification tanks. For cascades of tanks and batch reactors, dedicated blocks are available. Independent from these reactor models, the user can choose which activated sludge model is to be applied. Such models define a number of fractions of wastewater pollutants and micro-organisms as well as a number of chemical and biological processes which are considered important for the respective processes. For the description of reduction of organic load (COD) and nitrogen (nitrification, denitrification), the standard models ASM1 (Activated Sludge Model No.1) and ASM3 of the International Water Association (IWA) can be used.

Biochemical transformation models can be freely edited and modified in a user-friendly way using the SIMBA model editor, which is based on the Petersen matrix notation. Standard models (ASM1, ASM3, ADM1, RWQM1) are supplied with SIMBA.

These activated sludge models are implemented as predefined models in SIMBA:

  • ASM1hsg – Standard model of IWA with well-known modifications for improved applicability, parameter set from HSG simulation
  • ASM3m – ASM3 of IWA with parametrisation according to recommendations of HSG researcher´s simulation group
  • ASM3biop – ASM3 of IWA with an extension by EAWAG for biological phosphorous elimination

Users can define their own model blocks based on their own activated sludge models.

Model blocks for primary and secondary clarification

For the modelling of sedimentation processes in the primary and secondary clarifiers, a wide selection of models of differing complexity is available:

  • Simple model for primary clarification according to Otterpohl/Freud with COD elimination as function of residence time
  • Ideal sedimentation tank (ideal solid/liquid separation; no storage)
  • Ideal sedimentation tank with storage (solid/liquid separation user-configurable; simple storage)
  • 3-layer secondary clarifier model with variable sludge layer
Sewer systems

Hydrological and hydrodynamic modelling approaches

SIMBA# offers high flexibility for the selection of modelling approaches for sewer systems:

• Complete solution of Saint-Venant-equations
• Seemless integration and extension of computational kernel of SWMM5 (cf.

• Simplified, conceptual modelling
• Transport pipes within the sewer network
• Ancillary structures according to DWA-A 128
• Pollutant load calculations and long-term simulation

Arbitrary combination of both modelling approaches

Within SIMBA#, it is also possible, to model parts of a drainage network using a hydrodynamic approach (e.g. flat main collector sewers), whilst other parts of the same network (e.g. upstream subcatchments) can be modelled using a faster hydrologic modelling approach. This feature of SIMBA# allows you to adjust the complexity of a sewer network model to the specific needs of each particular project.

Each of these modelling approaches allows:

  • Uniform and non-uniform spatial distribution of rainfall
  • Arbitrary biochemical transformation processes within the network (modelling of the sewer as a physical, biological and chemical reactor)
  • Simple and complex open and closed loop control concepts
  • Analysis of RTC potential according to the German guideline DWA-M 180

Furthermore, SIMBA# allows the seamless integration of sewer system simulation with models of the other subsystems (WWTP, sludge treatment, river water systems).

User-friendly input and output, animation

  • User input and output, for example when defining the sewer network, are graphically supported
  • Freely configurable evaluation routines allow fast and easy evalutation providing textual and graphical information: Summary information (rainfall; discharge and overflow volumes and pollutant loads, storage utilisation), discharge frequencies and durations
Anaerobic processes

Anaerobic processes

The modelling of anaerobic processes (anaerobic wastewater treatment, sewage sludge digestion) increasingly gains in its importance due to continuous demands for the optimum energy operation of plants. Further incentives for the application of digestion models are given by the current developments within the biogas sector. The anearobic sublibrary provides options for the modelling of plants for anaerobic sludge digestion, anaerobic wastewater treatment and anaerobic fermentation of organic loads.

This dedicated library contains:

  • Various anaerobic models (Siegrist, simplified approach)
  • Model blocks for primary clarification with sludge removal
  • Model blocks for mechanic thickening as well as dewatering of sludge
  • Anaerobic reactor blocks (surcharge reactor, storage) with gaseous phase
  • Interface models for linking with activated sludge models
  • Integrated modelling of wastewater treatment and sludge treatment

Anaerobic models allow the prognosis of:

  • COD, TS degradation
  • Gas production, gas synthesis (carbon dioxide, methane, hydrogen)
  • Nitrogen release
  • Organic acids and pH
Receiving waters

River water quality simulation

SIMBA# allows the simulation of flows and water quality in receiving water bodies. Any arbitrary biochemical transformations can be modelled. A seamless integration with sewer systems and wastewater treatment models and also with contro algorithms is possible.

Flow calculation

  • Hydrologic flow modelling
  • Hydrodynamic flow modelling (work in progress)

Quality models

  • Can be specified and modified freely by the user
  • Predefined models available (e.g. SWQM, RWQM1, Lijklema)


  • River water quality simulation
  • Analysis of wastewater discharges from sewer system and WWTP
  • Assessment of urban discharges on river water quality according to the new guideline document oft he German federal state of Hesse
  • Integrated real time control
  • Sequential and parallel integrated simulation

Modelling approach according to Lagrange

An additional module contains the Lagrange modelling approach for pollutant transport, which allows transport modelling without the introduction of errors by numerical dispersion. The Lagrange modelling approach is based on the core principle of “water parcels“ moving along the river. Dedicated routines for the joining and splitting of these conceptual water parcels facilitate speed-optimised simulation.

Evaluation according to UPM Manual and BWK-M7

New evaluation routines for the analysis of results of river water quality simulation (work in progress)

  • Freely configurable textual and graphical output
  • Flows and water quality
  • Frequency-duration-based threshold values for oxygen, ammonium and ammonia according to the British Urban Pollution Management (UPM) Manual and to the German BWK-M7 document


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