gWATER technology

Industry-leading advanced process modelling software

gWATER is an internal product used for delivering PSE's water treatment plant optimisation services. We also provide gWATER to selected university partners for furthering R&D in the area of water treatment modelling.

gWATER's high-fidelity predictive models, implemented within PSE's gPROMS platform, enable rapid exploration of the process decision space for optimising of water treatment process design and operation.

They provide accurate information for reducing energy and chemical consumption, making informed decisions about current and future plant capacity and minimising capital and operational costs.

The gWATER environment

The diagram below shows gWATER features at a glance:

gWATER overview

Key features include:

  • High-fidelity models of all key unit operations, including biological and physio-chemical treatment reactors, solid/liquid separation units and various mechanical process units such as pumps and compressors
  • Models of advanced processes such as batch reactors, bio-filters, membranes, ion exchange, etc.
  • Steady-state and dynamic modelling, including dynamic optimisation
  • Whole-plant modelling capability, including the electrical side and all relevant control
  • Distributed systems modelling (i.e. partial differential equations / PDEs) to handle multi-dimensional conservation equations for accurate representation of process units such as clarification-sedimentation systems
  • Advanced parameter estimation capabilities to fit empirical parameters to dynamic (transient) operating data
  • Advanced optimisation capabilities, including whole-plant dynamic optimisation of the transient operation to minimise energy use, capital cost or any suitable objective function
  • Customisable web-based interfaces to allow easy delivery of sophisticated optimisation models to operations personnel
  • Online operation – open or closed loop – as part of the process automation system (PAS), exchanging data via OPC
  • Interfaces with other water software. gWATER models can be interfaced with runoff and sewer system models, to provide complete rainwater-to-river modelling.
  • Interface to CFD. Individual unit models can also be interfaced to CFD models using PSE's hybrid multizonal technology, to take into account mixing effects.

Technical details

gWATER provides a range of biological modelling capabilities, for example:

  • standard IWA ASM models
  • more complex plant-wide models capable of providing a complete representation of the plant by including the anaerobic digestion process
  • plant-wide models that can deal with all the relevant coupling between the water and sludge processing lines.

Customised biological models can also be constructed based on lab-scale or pilot-scale experiments, for example if a specific chemical compound needs to be considered because it is known that it will affect the biology.

All model compounds – organics and minerals – are fully defined in terms of atoms, meaning that it possible rigorously to check the atomic mass balances to verify results. The pH is also computed rigorously, based on ionic balances.


gWATER contains the following unit operations:

  • Aerobic process, especially aeration basin or activated sludge process
  • Anoxic/aerobic selector
  • Clarifier/thickener
  • Sludge Decanter
  • Anaerobic solid/sludge digester
  • Biogas treatment e.g. scrubber and utilization e.g. boiler, CHP.
  • Membrane filtration
  • Membrane bio reactor
  • MBBR
  • Sludge thermal Hydrolysis
  • Flotation / coagulation / flocculation
  • Ion exchange
  • Granulated sludge
  • Anaerobic reactor (UASB or similar high rate anaerobic WWT processes)
  • SBR


gWATER performs the following types of calculation, among others:

  • COD calculation and balance
  • Biomass growth and sludge production
  • Biogas generation calculation also with biogas quality (without sulphur)
  • Waste volume estimations
  • Electrochemistry-related calculations for ions
  • pH estimation
  • Inhibition model / kinetic
  • Energy performance

PSE is actively developing the biological and physical separation models in gWATER, as the latest published research becomes available.

Typical gWATER applications

gWATER can be used to model virtually any wastewater plant configuration. Below are a few flowsheet examples of common implementations used for plant design, operation and optimisation.

gWATER environment

Plant-wide flowsheet of a complex water treatment plant, including an anaerobic digestion process


gWATER environment

Multiple lines of activated sludge tanks. The optimiser can include integer/discrete decisions on how many trains to run for maximum efficiency.


gWATER environment

Two step bio-filtration process modelling

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