Prestressed Concrete Tanks Offer Cost Savings for Water Reclamation Facility Expansion Project

Located in the semi‐arid reaches of the Sonoran Desert in Tucson, Ariz., the Pima County Regional Wastewater Reclamation Facility (WRF) adopted a proactive approach to water reclamation to comply with federal standards.

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Located in the semi‐arid reaches of the Sonoran Desert in Tucson, Ariz., the Pima County Regional Wastewater Reclamation Facility (WRF) adopted a proactive approach to water reclamation to comply with federal standards.

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It was determined that prestressed concrete tanks offered the best tank structures for this project.

As part of the largest public works project ever undertaken in Pima County, the WRF expansion project included replacing the outdated Roger Road Wastewater Treatment Facility, built in the 1950s, with an innovative state‐of‐the‐art facility. In a public‐private partnership (PPP) with the WRF, CH2M HILL was awarded the contract to design, build and operate the plant.

It was determined that it would be less expensive to replace rather than upgrade the existing plant and that prestressed concrete tanks offered the best tank structures for this project. DN Tanks was hired as the tank prestressor for the project, which involved an 8.9-million-gallon (MG) bioreactor tank and a 5.0-MG chlorine contact basin.

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The WRF expansion project included replacing the outdated Roger Road Wastewater Treatment Facility with an innovative, state‐of‐the‐art facility.

The bioreactor, with a 33-foot wall height, 234-foot inside diameter and 14-inch thick, poured‐in‐place corewall, employed a unique five‐stage Bardenpho process for the removal of nutrients and organic pollutants during the treatment process.

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The project involved an 8.9-MG bioreactor tank and a 5.0-MG chlorine contact basin.

The 5.0-MG chlorine contact basin, with a 24-foot-by-6-inch wall height, 210-foot inside diameter and 12-inch poured in‐place corewall, served to regulate the transfer of chlorine from a container to flowing wastewater for purposes such as odor control and disinfection. A concrete wall in the middle of the basin split the tank into two separate units, allowing the tank to be drained without taking it out of service.

Upon completion, the sewage treatment plant will be able to meet Environmental Protection Agency (EPA) standards mandated by the Clean Water Act (CWA) for the amount of nitrogen, ammonia and other contaminants allowed in the treated water. Use of innovative treatment technology will produce the highest quality effluent, prevent odors and maintain water quality.

DN Tanks is an exhibitor at WEFTEC.14 and can be found at Booth 2228. For more information, visit www.dntanks.com.

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