Combatting Issues of Combined Sewer Overflows
The world’s largest compressible media filtration (CMF) facility, located in Springfield, Ohio, was recently completed, and it will help eliminate untreated wet-weather overflows – a significant issue facing many water utilities worldwide.
The innovative design includes the addition of a 100 million gallon per day (mgd) facility that is 10 times larger than the next largest of its kind. It features a robust and low-maintenance headworks, and the CMF technology is fully automated and does not require clarification chemicals.
“This facility is one of the first adopters of this emerging enhanced high-rate treatment (EHRT) technology to help wastewater treatment plants combat issues with combined sewer overflows,” said Bob O’Bryan, Project Manager for Black & Veatch.
The project also includes improvements to other plant process units to enhance capacity, operability and reliability. The upgrades include screenings, grit removal, final clarification, solids pumping, anaerobic digestion, biosolids handling and chemical feed.
Prior to these improvements, flows above approximately 40 mgd would discharge largely untreated as combined sewer overflow (CSO). Today, flows up to 134 mgd are treated to secondary effluent standards prior to disinfection and discharge to the Mad River, the largest coldwater fishery in Ohio. As a result, this project helps protect the quality of this important natural resource, which is a key local recreational amenity.
Black & Veatch was selected by the City of Springfield to provide study, design and construction management services for wet weather and capacity improvements at the facility. Biweekly workshops were conducted throughout the planning and design. The workshops included key stakeholders from the City of Springfield, the Ohio Environmental Protection Agency, the electric utility, and many technical experts. This collaborative approach allowed the project team to capture valuable input from stakeholders in the early stages of the project.
“Ultimately, this approach allowed the team to reduce the estimated costs from over $95 million to $60 million,” O’Bryan said.
Compressible Media Filtration
The CMF system selected was the WWETCO FlexFilter. This EHRT technology alternative provides a solution for CSO treatment that can both operate at higher flow rates and provide cleaner effluent compared to conventional clarification technologies. It can be used to both treat stormwater and sewer overflows and to provide polishing of plant effluent during normal, dry-weather conditions.
The CMF design is a simple gravity system requiring few moving parts. The influent liquid applies a lateral hydrostatic force through compression bladder sidewalls, causing the media bed to compress in a tapered fashion. This creates densely compressed media at the bottom that graduates to an expanded bed toward the surface, increasing the particle capture efficiency of the filter.
A key advantage to the CMF system is its automation – process control uses robust flow and level meters and timers without needing additional human operators. In addition, it requires no chemicals for most applications.
“We were very pleased to share our EHRT expertise with the city,” said Jim Fitzpatrick, Senior Process Engineer for Black & Veatch. “Black & Veatch designed similar facilities for Lawrence, Kansas, and Toledo, Ohio, that were the first and largest of their kinds in North America in 2003 and 2006, respectively. The Springfield CMF startup builds upon our tradition of bringing innovative solutions to our clients.”
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