A cell (#1-C @ 7.3 MG) was originally set aside for overflow treatment. After the primary cells, a flocculation cell (#2 – 0.05MG) was used for chemical addition (Ferric chloride). Cell (#3 @ 10MG), was used for settling of solids before entering a polishing cell (#4 @ 0.75 MG). Ultra Violet disinfection was used before final discharge thru a step aeration process then to Lake Huron.
In 2000, the mechanical aeration, in cells 1-A & 1-B, were replaced with a diffused air system, fed by 3 - 75hp blowers in a separate building. Cell 1-C was put on line as the settling pond, with mechanical aeration over the first 1/3 of the pond to help with settling. This was done to take advantage of the increased depth of Cell 1-C (12 ft.) over the previous Cell 3, which ranged in depth from 3 to 5.5 ft. The flow diagram shows the wastewater flow through the treatment system.
The collection system was also upgraded in 1986/87, infiltration was greatly reduced at this time. Two lift stations were upgraded and a new lift station (Reagan St.) was built to handle all the flow from the City and was the only pumping station to the Wastewater Treatment Plant. This main lift station was upgraded in 2000, by installing Variable Frequency Drives (VFDs) to the pump controls. This has greatly reduced the water hammer in the forcemain that had caused numerous failures.
St. Ignace Township, which is located directly to the North of the Treatment Plant, has been added to our WWTP, thru two lift stations that pump directly to the Plant. This project was completed in 2005, and the City operates and maintains the SITWSP system for the township.
In 2009, upgrades to the existing plant included, new UV disinfection system, screening, liners replaced in Cells 1-A,B &C, Cell 2, and Cell 4. A lift station was replaced, with a new forcemain from this station and the installation of Ductile Iron to replace the previous PVC forcemain from the main lift station.
Future plans include the replacement of 6,600 feet of new sanitary sewer (Portage Rd.) and abandonment of Cell #3, and replace with another Polishing cell, a twin to Cell #4.
Drying beds and biosolids removal improvements are also included. These are set for 2010 and 2011/12.