• Determine the impact of increased organic and hydraulic loading on an existing plant.
  • Verify plant capacity under different loading conditions, temperatures and or operating strategies.
  • Evaluate options for converting an existing plant that must meet new nitrification guidelines.
  • Compare alternatives for retrofitting an existing process (e.g. conventional activated sludge converted to IFAS).
  • Compare various BNR process configurations.
  • Investigate dynamic wet-weather performance, and determine best bypass or step-feed procedures.
  • Assess different diffused aeration design (e.g., diffuser design, taper and DO control).


  • Investigate the impacts of changing to a different operational strategy before implementing it in the field.
  • Study the impact of internal recycle rates, anoxic zones, and anaerobic zones on nitrification, enitrification and overall treatment level.
  • Model and evaluate the effects of taking specific digesters out of service with the goal to minimize the effect on sludge treatment.
  • Determine the effect on the plant performance if a rain event occurs while aeration tanks or clarifiers are taken out of service.

Operator Training

Combined with a plant-specific SCADA-like interface, GPS-XTM models can be used as an interactive training tool for treatment plant staff:

  • use the model to introduce new staff to the behaviour of the WWTP under dynamic conditions
  • illustrate the effects of changes to operational parameters (DO setpoints, RAS/WAS rates)
  • investigate wet-weather event strategies
  • determine the effects of diffuser cleaning on process performance, and estimate the optimum cleaning frequency

Cost Savings Investigations

  • Investigate the potential energy cost savings of implementing dissolved oxygen (DO) control or fine tuning existing DO control strategies.
  • Use the energy or chemical costing algorithms to estimate cost saving strategies under dynamic operating conditions.
  • Evaluate the most cost-effective options for upgrading (i.e.: install another reactor, add IFAS media, increase sludge handling capacity, etc.).
  • Balance the cost of sludge hauling and dewatering polymer addition by optimizing polymer dosage.
  • Evaluate phosphorus removal options for operating costs. Compare the operating costs of Bio-P (aeration and pumping costs) vs. chemical P removal (chemical addition costs) for your plant.


  • GPS-XTM is used as the primary research/development environment at many academic institutions around the world.
  • GPS-XTM serves as an effective research tool for investigating new process designs and strategies, as well as the development of new wastewater models.
  • GPS-XTM is offered in a multi-user site license configuration, useful for demonstrating wastewater treatment process engineering to undergraduate and graduate students.
  • GPS-XTM allows the students a 'hands-on' experience of running a virtual plant, and interactively seeing the relationships between key parameters and wastewater treatment performance.

Management and Strategic Planning

  • Capacity Analysis: by using future organic and hydraulic loading estimates, GPS-XTM determines when the plant will need to be expanded or upgraded.
  • Modeling can be carried out quickly to answer any operational questions associated with taking processes out of service.
  • Construction timing can be optimized by estimating the effects of various service reductions on plant compliance.
  • Treatment plant owners can use GPS-XTM to evaluate/confirm plant designs being submitted by consultants.
  • GPS-XTM can be used to reduce the cost of pilot plant operational studies by reducing the need to operate under certain conditions (i.e.: SRT's that require long operating periods and hence increased costs).