Wastewater facilities face varying conditions that impact the effectiveness of treatment methods, from fluctuating temperatures to changing community treatment needs. Process modeling enables utilities to evaluate various treatment technologies or processes virtually, rather than using trial and error on physical plants or costly pilot and bench-scale studies.

Process modeling can simulate different microbial reactions within the wastewater treatment process simultaneously, within minutes. It enables evaluation of various treatment technologies, flow and loading conditions, and compliance targets in a thorough, efficient manner. A process model can be developed based on the utility’s specific needs, supporting efforts to take the facility from the planning phase to choosing an approach and through implementation of the finalized solution.

Process models can be useful for evaluating a variety of financial and operational factors:

  • Capital cost: Capital cost is often a project driver, helping determine why one treatment approach is selected over another. A process model allows evaluation of multiple treatment alternatives and flow and loading conditions in an efficient manner.
  • Compliance: Effluent permit requirements have significant cost implications, and often the improvements needed to remain compliant require large capital projects. Process modeling quantifies plant performance and predicts compliance under varying conditions.
  • Operations and maintenance cost: Operational parameters can be added to the process model to predict energy demand and operating costs, improve operational efficiency and help the municipality plan for ongoing costs.

Process Modeling in Action: A Case Study

A project in Hays, Kansas, offers a prime example of the benefits of process modeling in action. The City had new total nitrogen and total phosphorus limits to comply with that required a large capital improvement project. The City had a strict budget for the improvements that required an innovative solution — a single-basin cyclic aeration process.

The project design had to adjust to a single-basin infrastructure layout while providing contingency plans for the event of that in-basin equipment being out of service. The model was adapted for these design accommodations and continued to deliver value by providing real-world data to the plant staff, comparing what occurred in the model to what was actually happening as a result of the applied treatment plan. The process model — and the resulting treatment approach — saved the city both time and money by enabling insight-based adjustments as a solution was identified and implemented.


Learn about how the design-build project delivery method was used to help the City of Hays upgrade its wastewater treatment plant.

Read the Case Study

Caitlin Prim, PE, is a section manager and an environmental engineer at Burns & McDonnell. With a career spanning more than a decade, she has extensive experience delivering successful municipal wastewater and water treatment plant design projects.