Due to the City's aging plant that had been upgraded multiple times and had difficulty meeting IDNR requirements, I+S Group (ISG) recommended a new system consisting of a covered two-cell aerated lagoon with a polishing reactor (LemTec™) and UV disinfection. A sewage grinder was included in the inlet structure for the lagoon. The existing collection system had two separate force mains, an existing 6-inch line and an 8-inch installed with the bypass storm water pump. These two lines were extended and flow meters were added to each force main to measure the flows coming from both systems.
ISG designed the covered aerated lagoon to handle the increased loading from the Infiltration and Inflow (I/I), and retain heat during winter months which decreases the footprint needed for the nitrification process in the polishing reactor. This was a benefit to the City since there was a limited allowable footprint for the facility.
The covered aerated lagoon system allows the City to attain the level of treatment required by the IDNR stream standards and the excess I/I. The operation requirements are now consistent with the City's mechanical plant.