Client: Sanitary District of Decatur

Location: Decatur, Illinois

The Sanitary District of Decatur owns and operates an advanced wastewater treatment facility with a 41-mgd average day capacity and 125-mgd peak capacity. The District retained Donohue to develop a planned approach for biosolids equipment replacement, process improvements, and future issues.

Donohue identified system capacity and needs through 2030, developed and evaluated 54 potential alternatives, recommended alternatives, and developed a three-phased (near-, mid-, and long-term) approach to addressing present and future issues. This roadmap will guide District priorities and direction for many years.

Following plan completion, Donohue designed a High Strength Waste Receiving Station to allow the District to convey 70,000 gpd of high strength food processing waste directly into the District’s four primary anaerobic digesters, increasing digester gas production.

Additionally, Donohue recently designed the replacement of the digesters’ existing Pearth gas mixing system with a linear motion mixing system. The new linear motion mixing system is being installed in the 100-foot diameter digesters that are all equipped with floating covers. The project also includes several upgrades to the complex’s piping and ventilation systems to comply with NFPA 820 standards. 

Donohue is currently designing sludge thickening improvements.