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overflow," explained Douglas Dietzel, a process specialist at the Westerly plant. "So, as part of our agreement with the EPA, we're increasing our ability to treat wastewater during high- flow events." The Westerly plant, which sits on the shore of Lake Erie, is Cleveland's oldest wastewater treatment site (constructed in 1922) and serves approximately 103,000 residents. The plant processes an average flow of 26 million gallons per day (MGD) of wastewater, and its Combined Sewer Overflow Treatment Facility (CSOTF) provides storage for six million gallons and preliminary treatment for up to 300 MGD during wet-weather flows. In the CSOTF, the heavier organic material is allowed to settle out of the wastewater, but the flow can still contain pathogens when it is returned to Lake Erie, since it does not pass through secondary treatment or disinfection. Chemically Enhanced Treatment A new project, called Chemically Enhanced High Rate Treatment (CEHRT), will expand the overall size and scope of the treatment process with the inclusion of chemical storage and feed facilities, providing treatment and disinfection capabilities absent from the current system. CEHRT is actually two acronyms combined: Chemically Enhanced Primary Treatment (CEPT) and High Rate Disinfection (HRD). CEHRT is an advanced way of treating wastewater overflow by speeding up the natural, gravity-based settling process used in the normal treatment process (through the addition of chemicals) and providing disinfection. "Coming into the plant is all this negatively-charged organic material," explained Dietzel. "We neutralize that charge with fer- ric chloride, which has a positive charge. Then we use an anionic polymer, a long chain of hydrocarbons, to stick to all of those sus- pended particles." The polymer creates a "floc," meaning that the sus- pended organic parti- cles clump together and settle out of the water. The flow then goes to the HRD tank, where sodium hypochlorite, a strong bleach, is added to kill off any remain- ing pathogens. "Instead of having just settled wastewater, you have treated flow safely going back out into the lake," said Dietzel. The EPA gave the district an opportuni- ty to demonstrate the effectiveness of lower- cost treatment options like CEHRT through pilot demonstration projects. If successful, the district would be able to avoid imple- mentation of the more costly ballasted floc- culation treatment technology. "The EPA initially wanted us to use a much more expensive sand-injec- tion process," said Dietzel. "They gave us three years to test out CEHRT at all three of our plants, and if it worked we could use it." The plants have utilized a bench test to determine the optimum amounts of ferric chloride and polymer to get the process to work. "Based on our testing, we see that CEHRT works very well," said Dietzel, noting the contrast between the brown, muddy wastewater and the clear, post-CEHRT efflu- ent. If given the go-ahead by the EPA, the CEHRT systems could be fully operational at all three district plants as early as December 2021. Project Clean Lake means a cleaner Lake Erie. But, with a $3 billion price tag, it also means that rates will increase. As the district's main source of revenue, customers' sewer-bill payments will fund these construction projects and plant enhancements, and rate increases will be significant. The success of the CEHRT pilot program, and opportunities to optimize projects through advanced planning and value engineering, will help the district minimize Project Clean Lake's financial impact on its ratepayers. "The CEHRT system is relatively new, and very few wastewater agencies in the U.S. use it," said Dietzel. "We are the first large sewer authority to do something like CEHRT. It will save our ratepayers money, and that's our goal." n 12 wateronline.com n Water Innovations CONTAMINANTREMOVAL Michael Uva is the senior communications specialist at the Northeast Ohio Regional Sewer District. About The Author The beaker at left shows influent before the CEHRT process; at right, effluent after CEHRT. At the Westerly plant, a polymer blend unit makes a polymer solution for the CEHRT process.