In anticipation of new permit conditions and lower phosphorus limits, the City of Joliet and Donohue & Associates, Inc. worked collaboratively to implement biological nutrient removal and other improvements at Joliet’s wastewater treatment facilities.

At Aux Sable, upgrades included grit removal facilities, activated sludge selectors for biological phosphorus removal, oxidation ditch hydraulic modifications, two final clarifiers, UV disinfection expansion, aerobic digester covers, RAS pumps, biosolids storage tank, and chemical feed facilities.

The selectors allow the plant to operate in three different biological phosphorus removal modes to best match current operating conditions. The improvements also provide additional treatment capacity.

At Westside, chemical phosphorus removal facilities were added based on site constraints and influent characteristics.

The project resulted in the unique ability to trade total phosphorus performance between the City’s three wastewater facilities to meet lower phosphorus limits and reduce operating costs. This is the first trading arrangement approved by the State of Illinois.

The successful $17 million construction project impacted every structure on the Aux Sable site. A well-executed sequencing plan helped achieve zero permit violations while maintaining continuous plant operation during construction.