Reducing Operations and Maintenance Costs through a new Nutrient Recovery Facility 

The Tres Rios Water Reclamation Facility is the centralized biosolids processing facility for Pima County’s eight WRFs. In addition to the task of cleaning wastewater, the Pima County Regional Wastewater Reclamation Department opted to facilitate the capture of energy and nutrients, specifically the capture of phosphorus as struvite, which has a market value as a fertilizer additive. 

HDR provided progressive design-build services for an approximately US$6 million struvite sequestration system to reduce struvite formation potential, reduce ferric acid and polymer use, and improve the dewaterability of the solids handling process.

The scope of this project involved designing and constructing a nutrient recovery facility for the purpose of reducing operations and maintenance costs, as well as increasing the nutrient recovery capacity through the use of a waste activated sludge pre-treatment process. The design-build delivery best suited the project because of the team collaboration, cost savings, specialty nature of the struvite recovery process, and incentives to expedite delivery.

We prepared a performance specification, which was distributed to two technology vendors for cost proposals. This allowed Pima County to select NuReSys as the most cost-effective technology. HDR worked with NuReSys to ensure their vendor package was fully consistent with the County’s Regional Optimization Master Plan Specifications so that the mechanical, electrical, and controls components were consistent with those at the Tres Rios WRF, thereby simplifying the future O&M requirements. 

Throughout the design, we scheduled weekly coordination calls with NuReSys’ engineers to ensure both designs were consistent. We also prepared for and submitted both local building permits as well as the State Aquifer Protection Plan Permit, which was quickly approved without review comments. This highlights the accuracy and quality of design documents prepared.

Ongoing collaboration and communication between HDR, the County and the technology vendor was the key to success for a thorough, responsive design that resulted in expedited construction with few unknowns and limited need for contingency.