STV’s innovative design for the wastewater treatment plant expansion in Owasso, OK, earned the Grand Conceptor Award from the American Council of Engineering Companies in Oklahoma (ACEC OK)—the highest engineering achievement award from the organization.  

The Owasso Wastewater Treatment Plant Expansion (WWTP) is one of the largest initiatives that the City of Owasso has ever undertaken. STV served as the lead designer and engineer-of-record for the first phase of the plant’s expansion. The team designed improvements to Owasso’s main pump station, headworks facility, aeration basins, blowers, digesters, and non-potable water system, as well as two new electrical buildings and generators and other key infrastructure for the plant’s operations. STV was part of the project team with Crossland Heavy Contractors and subconsultant Freese & Nichols.  

With its approximately 38,000 residents, Owasso is one of the fastest growing cities in Tulsa and Rogers counties—yet its wastewater treatment plant faced capacity limits due to an undersized aerobic digester and aging equipment nearing the end of its lifecycle. 

Owasso’s Public Works Department, the project’s owner, embarked on an ambitious plant expansion project in 2017 that would not only improve its facilities and effluent quality, but also reduce the plant’s energy consumption and its potable water usage significantly.  

STV leveraged advanced blower technology and designed anoxic zones that have contributed to the plant’s reduction in energy consumption by over 30% and a significant improvement to the plant’s effluent quality—resulting in safer, cleaner water downstream.  

“We configured the new aeration basin with a pumping system that recycles effluent to anoxic zones. These low oxygen zones use nitrates in place of oxygen to support bacteria respiration, which further reduces energy consumption and reduces nitrogen in the effluent,” said Michael Graves, PE, principal and the project manager for the Owasso WWTP expansion. “We configured the treatment system to allow both the existing and new aeration basins to ‘share’ in the anoxic zones, which further reduced energy demands and effluent nitrogen.”  

The addition of the new aerobic digester with improved mixing and aeration systems has reduced biosolids disposal in the landfill by 30%. Since the project’s substantial completion, the plant has lowered levels of biochemical oxygen demand (BOD) and ammonia in its effluent. A new non-potable water system at the plant has reduced potable water usage by 60%, compared to levels prior to construction.  

The City of Owasso estimates approximately $250,000 each year in operations cost savings. 

From l to r: Tim Gatz (ODOT Executive Director), Michael Graves, Andrew Doerflinger and Cameryn Edwards.

“This project had a positive impact on the entire community and improved the ecosystem. I’m so proud of the team, our client, and our partners. We’re honored to receive this award,” Graves said. 

Featuring advanced technology and innovative design, the Owasso WWTP project provided the city with a modern system with built-in capacity for future growth, especially as the expansion enters the second phase.   

“We’re thrilled that ACEC OK recognized the Owasso wastewater treatment plant expansion project with its Grand Conceptor award as it reflects the sheer significance of this project to not only the city of Owasso but to the entire state,” said Marisa Vergara, PE, senior vice president and regional director for water.