Water & Wastewater Treatment

www.wwtonline.co.uk | WWT | NovemBeR 2015 | 21 Project focus Wastewater treatment CMF technology strengthens wet weather resilience Project focus C hanging rainfall patterns and increasingly stringent environmental protection standards are challenging the way water utilities the world over manage storm flows. An interesting approach can be found in Springfield, Ohio, U.S.A. The city recently added an enhanced high-rate treatment (EHRT) facility featuring the world's largest compressible media filtration (CMF) system. The innovative project has added significant peak wet-weather ● Compressible media filtration used in Springfield, Ohio ● Overflow treatment facilities offer alternative to storage and conveyance ● Automated, remotely-controlled solution proves cost effective ● Untreated CSO flows needed to be reduced to the Mad River, an important watercourse for cold water fishing ● Extra capacity was required to accommodate and deal with additional flows during wet weather events ● Remote operation was preferable to allow the solution to be available 24/7 without being reliant on operators • Drivers facilities that incorporate best- fit advances in technology can offer a cost-effective alternative to new storage and conveyance infrastructure. The Mad River flows through Springfield and is the largest cold water fishery in the state of Ohio. Its watershed drains more than 1,550 square kilometers, with about two-thirds of it used as crop and pasture land and one-fiŒh for urban-residential use. Approximately 170,000 people reside in the area. Water quality in the Mad River watershed is impaired by a number of sources. They include excessive nutrients such as nitrogen and phosphorus from fertilisers, animal waste and sewage, which enter the watershed during wet-weather events. Polluted runoff from urban and agricultural areas is a culprit as is excess siltation resulting from stream channelization. Wet and dry capability Springfield is served by a wastewater treatment plant that has an average design flow of 95 million litres per day and provides treatment of dry- weather flows through conventional preliminary, primary, trickling filters and nitrifying activated sludge processes. The plant has overflow weirs that discharged excess wet- weather flows largely untreated to the Mad River. Most of Springfield's collection system is separate sanitary sewers, but about 22 percent of the system consists of combined sanitary and storm sewers, including 57 combined sewer overflow (CSO) outfalls. During wet weather events when infiltration and inflow through the combined sewers exceeds capacity, discharges through the CSO outfalls go untreated into the river. According to Ohio's Environmental Protection Agency, CSOs impacting flow capacity – 380 million litres a day (ML/d) – to Springfield's publicly owned treatment works and serves to reduce untreated overflows into the local river. Moreover, the CMF technology is fully automated, does not require clarification chemicals, and its capital and operating costs are a fraction of those associated with an expansion using conventional storage, conveyance and treatment technologies. The lesson from Springfield: overflow treatment Tony Koodie euRopeaN pRocess DiRecToR Black & veaTch The CMF cells in the Springfield facility are the largest of their kind

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