The Metropolitan Water Reclamation District of Greater Chicago provides wastewater treatment and stormwater management services for residents and businesses in the Chicagoland area. Its service area covers 882 square miles, including the city of Chicago and 128 suburban communities in Cook County. MWRDGC serves approximately 10.35 million people each day, including 5.25 million residences.
MWRDGC operates seven facilities: Stickney, Calumet, Terrence J. O’Brien, John E. Egan, Kirie, Lemont, and Hanover Park water reclamation plants. These facilities had a combined discharge of approximately 535 billion gallons of treated water in 2019, and 448 billion gallons in 2020. Due to the large volume of water that is discharged, the nutrient contributions from these facilities comprise a large percentage of the annual statewide loads. MWRDGC facilities contributed 38% and 42% of the annual statewide total phosphorus loads in 2019 and 2020, respectively. These seven water reclamation plants discharged approximately 5.6 million pounds of phosphorus in 2019 and 6.3 million pounds in 2020. The Stickney and Calumet WRPs comprised a majority of these loads.
Most of the statewide reduction in total phosphorus reported in the 2019 biennial report was due to large reductions from the Stickney facility. The implementation of a biological phosphorus removal system in 2014 was optimized in 2018, resulting in a 95% phosphorus removal efficiency. However, problems arose with managing solids content in the aeration tanks in January 2019. The biological phosphorus removal operation was halted and slowly restarted during 2020. To ensure compliance with the permit limit of 1 mg/L that goes into effect in August 2021, a temporary chemical phosphorus removal system is being installed, which will be followed by installation of a permanent chemical phosphorus removal system.
The Calumet WRP discharged the highest statewide total phosphorus load in 2020. A phosphorus removal feasibility study was completed in 2019 and a chemical removal process is currently being designed to work in concert with a biological phosphorus removal system. The Calumet facility’s current NPDES permit includes a schedule for achieving compliance with a total phosphorus limit of 1 mg/L by January 1, 2024.
The O’Brien WRP is MWRDGC’s third largest facility. A phosphorus removal feasibility study was completed in 2019. A pilot test using algae for nutrient removal is currently underway and a side-stream enhanced biological phosphorus removal system was initiated in 2020. The facility’s current NPDES permit includes a schedule for achieving compliance with a total phosphorus limit of 1 mg/L by August 1, 2027.
It is anticipated that significant reductions in total phosphorus loads from point sources will be achieved once these three facilities, along with other large major municipal facilities throughout the state, meet a 1 mg/L total phosphorus concentration. As demonstrated by other facilities, achieving annual average concentrations at or below 0.5 mg/L is possible, which will lead to even further reductions for statewide total phosphorus loads.
