Filtering Wastewater More Efficiently

Filtration system saves water, money for City of Sioux Falls

Article ID: 619934

Released: 26-Jun-2014 4:50 PM EDT

Source Newsroom: South Dakota State University

  • Credit: Photo by Eric Landwehr

    Backwashing these monomedia filters takes only 10 minutes and saves Sioux Falls, South Dakota, an average of 1 million gallons of water per day and approximately $12,000 per year in labor and energy costs.

  • Credit: Photo by Eric Landwehr

    Operations supervisor Mark Hierholzer of the Sioux Falls Water Reclamation Plant checks the control panel, which makes backwashing automatic via a programmable logic controller. This also allows staff to do the backwash in the evenings during off-peak demand periods when power costs are lower.

  • Credit: Photo by Eric Landwehr

    It sounds like a jumbo jet revving up its engines for takeoff, but this blower system uses air at 10 to 14 psi to dislodge particles in the monomedia filters and thus requires less water. This means big savings for the City of Sioux Falls.

Newswise — An estimated 1 million fewer gallons of water must be treated daily at the Sioux Falls Water Reclamation Plant, thanks to a filtration project done in collaboration with the South Dakota State University Water and Environmental Engineering Research Center, the City of Sioux Falls and the city’s consulting firm, H.R. Green Engineering of Cedar Rapids, Iowa.

For more than a decade, the City of Sioux Falls has set aside $20,000 each year from its capital improvement program to fund graduate research that will increase the efficiency of its wastewater treatment plant. The City of Sioux Falls and its taxpayers have reaped the rewards of investing in research and serve as an example for what other communities might be able to accomplish through a partnership with the Water Research Center.

Selecting a new filtration systemIn 2010, the Sioux Falls Water Reclamation Plant set out to replace the filters that trap the remaining solids just before wastewater is released into the Big Sioux River. The goal was to increase the flow rate through the filters and automate the backwash system, according to Mark Perry, wastewater superintendent for the City of Sioux Falls. The price tag for replacing the filters was $3 million.

The plant’s dual-media filters, which use a combination of anthracite and sand to filter water, were operating well beyond their design life, explained Chris Schmit, director of SDSU’s water research center. The filters would clog and then have to be backwashed every 24 hours.

Finding a simple, efficient solutionWith guidance from Schmit, graduate student Sean Sieler worked with H.R. Green Engineering and the City of Sioux Falls to come up with a filtration system that would meet the city’s needs.

“We used an old technology called a monomedia, unstratified deep bed filter, which utilizes only coal and a deep bed,” Schmit explained. The media, which is much larger than conventional filter media, lets more water through, holds more solids and doesn’t clog as quickly. The filter only needs to be backwashed once every three days to remove deposits and the process uses half as much water as the previous backwash method, Schmit noted.

The plant was able to maximize its hydraulic capacity because the monomedia filters could handle twice the amount of water as the old dual-media filters, Perry explained. By doubling its capacity, the plant was able to meet the city’s needs without having to build a second filtration building that would have cost about $10 million.

The filters have to be backwashed less often and the backwashing only takes 15 minutes, resulting in more than a 50 percent savings in time alone, according to Perry.

Backwash water has to be reprocessed, so any water savings essentially doubles, Perry said. The plant also gained 800,000 to 900,000 gallons a day in capacity, “because we don’t have to send that water to the head of the plant again.” Changes in the filtration system have also improved the quality of the water being released into the Sioux River, Perry explained. Essentially, the water that the plant releases is “cleaner than what’s normally in the river.”

Gaining recognition for innovation The water filtration project has proven the value of investing in research for the City of Sioux Falls, one that has been recognized by engineers nationwide. Two papers were published in the Water Environment Federal magazine and presentations given at national Water Environment Federation Conferences in 2012 and 2013. The City of Sioux Falls, H.R. Green Engineering and SDSU also received the 2012 Annual Honor Award from the American Council of Engineering consultants of South Dakota and the 2012 Annual Outstanding Engineering Achievement award from the South Dakota Engineering Society.

About the Water and Environmental Engineering Research Center The Water and Environmental Engineering Research Center is located in the Jerome J. Lohr College of Engineering at South Dakota State University. It conducts research, education and outreach activities through principal investigators who are faculty members. Research projects are funded by governmental agencies, cities, and industry, and are focused on engineering solutions to water resources and environmental problems. Projects often involve collaboration with other SDSU departments or off-campus units.

The center also maintains a water and wastewater analytical laboratory in Crothers Engineering Hall in conjunction with the Civil and Environmental Engineering Department. The laboratory supports research projects, environmental engineering courses, and outreach/service activities.

About South Dakota State UniversityFounded in 1881, South Dakota State University is the state’s Morrill Act land-grant institution as well as its largest, most comprehensive school of higher education. SDSU confers degrees from eight different colleges representing more than 175 majors, minors and specializations. The institution also offers 29 master’s degree programs, 13 Ph.D. and two professional programs.

The work of the university is carried out on a residential campus in Brookings, at sites in Sioux Falls, Pierre and Rapid City, and through Cooperative Extension offices and Agricultural Experiment Station research sites across the state.


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