The Portland, Ind., Wastewater Treatment Plant had been using six granular-media filter units with a design average flow of 2.35 MGD for tertiary treatment since the 1980s. The filters required daily maintenance due to valve issues, broken underdrains, and loss of media. According to Robert Brelsford, superintendent, “Not a day went by that we didn’t have to work on them.” Besides these issues, “the system required about 10,000 gallons per backwash,” he added.
In the fall of 2011, project engineers Jones & Henry Engineers Ltd., of Fort Wayne, Ind., took a closer look at the six tertiary filters, and determined they were not repairable. Instead, the recommendation was to install two new cloth media disk filters, each with a capacity of 4.7 MGD.
One of the critical issues they investigated was the choice between an “outside-in” design versus an “inside-out” design. The former was chosen because it would be easier to clean, based on input from plant operators and maintenance personnel at the facilities sited. “Our secondary clarifiers have a lot of moss,” said Brelsford, “which would get trapped and be hard to get out in an inside-out configuration.”
With a fast-track design-build process, the Portland Wastewater Treatment Plant went from design work to project completion in a little over 12 months. Meeting this very compressed timeline ensured that the plant would receive SRF funding.
The tertiary treatment system was completely renovated by adding two Aqua-Aerobic AquaDisk filters, each comprising 10 disks and capable of handling peak flows of up to 4.7 MGD (total treatment volume for both filters is 9.4 MGD). Each disk is fitted with OptiFiber® cloth filtration media designed to maximize solids removal over a wide range of particle sizes. Its thick pile construction allows filtered solids to be stored, unlike microscreen media, thereby extending the time between backwashes. A uniquely designed cloth-fiber-backing support structure promotes thorough cleaning of the media for optimum performance.
In operation, either one of the AquaDisk filters can handle the treatment capacity of the six previously used granular media filters, providing flexibility for routine maintenance and future growth. Backwash volume has been reduced 97 percent, to about 300 gallons per backwash. Additionally, energy consumption has dropped dramatically because so much less water is pumped back through the system. “The filters have worked great since we put them in,” Brelsford noted. “I would highly recommend the AquaDisk filter. Anyone can come and visit our plant and see the technology for themselves.”
Aqua-Aerobic is exhibiting at WEFTEC.17, Booth 3801. For more information, visit aqua-aerobic.com.