City of Port Clinton, Ohio
In response to Federal Findings and Orders and Consent Decree CT Consultants guided the City of Port Clinton through the negotiation process and performed all the necessary work to achieve one of the first five Long Term Control Plan (LTCP) approvals in the state of Ohio. The resulting CSO program was designed to meet the NPDES compliance schedule and yet be affordable.The majority of the City of Port Clinton’s collection system is combined with a small area served by a separate sewer system. The combined system at the time still had five CSOs. An extensive study was performed on the existing system and included survey, flow monitoring, and mapping to create a comprehensive collection system base map. This data was then modeled utilizing XP-SWMM software. The model showed that the existing sewer system was capable of capturing well in excess of 85% of all storm flows while directing this flow to the WWTP. Separation alternatives were analyzed but due to the enormity of costs the study focused on plant options. Equalization (EQ) was considered but because the existing plant site is limited this option would have required plant relocation. Research was performed to determine any high rate treatment options. This effort became the focus after negotiations concluded the EPA would accept primary treatment limits with disinfection on storm flows.
The existing WWTP had an existing rating of 1.2 MGD Average Daily Flow with a peak of 3.0MGD based on stress tests. The model calibrated with the derived “typical rain event” which was derived as part of the study showed the plant would need to treat 25 MGD in storm mode to meet the required number of overflow events.
CT Consultants’ research identified a process (ActiFlo) being utilized in Europe that could be utilized as the high rate treatment option. Using a process called ballasted floc the system foot print was exceedingly small considering the flow rates being treated. Calculations indicated the process could be situated on the existing site. However, the process had not been qualified to be used in a Combined Sewer System. An R&D grant was obtained to perform a pilot which gained EPA acceptance. The advantage of this process was that the effluent water quality far exceeded primary treatment standards. The system is also capable of responding quickly to rain events.
The resulting LTCP utilizing high rate treatment was approved without comment. The City of Port Clinton moved quickly to design and construct the ActiFlo system and substantial improvements to its secondary and solids handling process. The final construction cost was $14.5 million for the WWTP improvements which was substantially lower than sewer separation.