Delivering the Biggest Bang for the Wet Weather Treatment Buck – Success of the NEORSD Chemically Enhanced High-Rate Treatment Demonstration Program

The Northeast Ohio Regional Sewer District (District) is currently implementing pilot- and full-scale demonstrations for the chemically enhanced primary treatment (CEPT) and high rate disinfection (HRD) of its wet weather flows at its three wastewater treatment plants in the Greater Cleveland Metropolitan area in response to a Consent Decree (CD) entered into with the Environmental Protection Agency. During wet weather conditions, operations staff members are deployed to operate and measure the performance at each of the facilities. A number of challenges exist, including inherent intermittent operations, unpredictable wet weather, and changing influent water quality characteristics, all of which can adversely impact performance of these facilities. Despite these challenges, performance results demonstrate an average effluent TSS of less than 40 mg/L at all three plants at sustained surface overflow rates (SORs) ranging from 81.5 to 415.5 m/d (2,000 to 10,200 gpd/sq ft). HRD testing results conducted to date show the capability to achieve 126 CFU/100 mL at dosages of 6 mg/L of chlorine at contact times of less than 10 minutes. By demonstrating performance criteria can be met, the District will have flexibility and maximize existing infrastructure during full-scale implementation and save more than $200 million in capital and operating costs when compared to the CD stipulated alternative treatment technology. Further cost savings can be realized by maximizing the removal performance at high SORs and low disinfection contact times.