IIW has a long history of providing engineering services to the City of Dyersville. The original mechanical WWTF at the current site was constructed in 2001-2002. This project, now referred to as Phase I improvements, primarily included an influent lift station, a headworks/administration building with mechanical fine screening and grit removal, a three-channel oxidation ditch, two circular secondary clarifiers, and two circular aerobic digesters.
Due to continued City growth, the necessary frequency of sludge removal from the aerobic digesters created operational problems. As a result, the Phase II project was completed in 2010 and included the construction of a sludge processing building to house a belt filter press for sludge dewatering. The project also included the installation of variable frequency drives (VFDs) for the aeration system at the oxidation ditch. The Phase II project for the Dyersville WWTF received 20% CWSRF loan forgiveness through the American Recovery and Reinvestment Act of 2009 due to an increase in energy efficiency.
Due to the results of influent sampling subsequent to the Phase II improvements, an increase in overall treatment capacity was required in order for the City of Dyersville to continue to grow. As was ultimately intended during the design of the Phase I improvements, duplication of the existing secondary process (oxidation ditch and secondary clarifiers) is now under construction. This project, referred to as the Phase III expansion, also includes installation of an ultraviolet light (UV) disinfection process. Funding for the Phase III expansion project included a $1,000,000 disaster resiliency grant from the federal Economic Development Administration.