Streamlining water treatment plant operations with an InfoWorks ICM digital twin

Tasked with protecting and maintaining the largest river basin entirely within the state of Texas, the Trinity River Authority (TRA) has its work cut out for them. In the northern region of the Trinity River Basin, TRA operates five major wastewater collection and treatment systems serving municipalities in one of the fastest-growing metropolitan areas in the United States. This responsibility requires a combination of keeping an eye on the future and a firm grip on the development and implementation of operational improvements in the present. One way they do that is by relying on hydraulic models as digital twins of their working systems.

TRA has lots of helpful resources on their website like this watershed map.

The importance of RDII in wastewater operations

Sanitary sewer systems are, by design, closed systems. This means that, in theory, these wastewater systems shouldn’t be influenced by weather events like rain. However, any water or wastewater professional knows that this isn’t the case. Rainfall Derived Inflow and Infiltration (RDII) can drastically affect wastewater operations.

TRA works directly with their customer cities, providing annual reports of RDII and running near continuous master planning updates across their basins. Each basin is different, of course. For example, one unique issue with RDII is observed in the southwestern Dallas-Fort Worth (DFW) Red Oak Creek sewer basin. Specifically, this basin experiences extremely long wet weather tails or heightened flow rates for an extended period of time after a storm, increasing the overall volume in need of treatment resulting in operational challenges and unpredictability in sewer loading.

The Red Oak Creek treatment plant regularly wins awards for its pastoral landscape design.

Correctly modeling and planning for these prolonged flow rates has been a primary focus of the TRA Planning Design and Construction Administration (PDCA) group. The PDCA works alongside field, treatment and engineering staff to ensure the effective use of funds, efficiency in operations, longevity in capital improvements, and an accurate hydraulic representation of their modeled wastewater systems. In keeping with these goals, the planning team performed an in-house master plan of their Red Oak Basin using InfoWorks ICM.

Holy grail: modeling RDII in real time

“Let’s say it’s been raining for two weeks,” posits TRA Modeling Analyst Andrew “AJ” Czubai. “How big of a storm can we handle right now?” Without a proper hydraulic model, answering this important question involves quite a bit of guesswork. However, by being data-driven with their process, PDCA knows they can answer this question empirically. The team blocked off a few months to tackle the best approach for studying and replicating the RDII issues in these two systems.

The Red Oak Creek Regional Wastewater System (ROCRWS) in the southwestern part of the greater Dallas-Fort Worth area experiences abnormally long rainfall responses. Even in dry conditions, a small 1-inch rain event is enough to elevate average flows up to 20% for up to a week before flows return to their normal average daily flow. The effect is noticeably worse when antecedent conditions are saturated from a previous “soaking event” or heavy storm.

The core of how TRA approached the problem was understanding peak flow rates and accurately modeling flow. “On the collection side, we tend to focus on the peak flow rates a pipe can convey, which is a driver for costing and project sizing,” AJ explains. “However, prolonged elevated flows for a few weeks also impact the overall volume of flow that needs to be treated, which means additional chemical costs, heavier run time on pumps, and potential permit violations if not anticipated. By being able to estimate future wet weather volumes, you’re able to plan for and adjust your treatment strategy.”

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Taxonomy

• Digital Twins