The Metropolitan Water Reclamation District of Greater Chicago, which operates the largest wastewater treatment plants in the state, adopted a resource recovery approach to reduce total phosphorus in the effluent from its largest water reclamation plants. When permits for the Calumet, Stickney, and O’Brien plants were renewed in 2013, the implementation of monthly averages of 1 mg/L total phosphorus effluent limit was included for the next 4–10 years. The district worked directly with Illinois EPA, with input from Illinois Association of Wastewater Agencies and environmental groups, to negotiate permit conditions.
National Pollutant Discharge Elimination System permits for the three plants mentioned above were appealed to the Illinois Pollution Control Board and Illinois Appellate Court for the First District concerning the appropriateness of the 1 mg/L total phosphorus effluent limit. A coalition of environmental groups argued that the permit limit of 1 mg/L was not protective against violations of Illinois water quality standards regarding dissolved oxygen, offensive conditions, and unnatural sludge.
The outcome of the permit appeal was a settlement agreement. The terms of the settlement agreement were modifications of NPDES permits to include the following:
- A nutrient oversight committee will be established to prepare a nutrient implementation plan.
- MWRD is responsible for installing a water quality monitoring station on the Des Plaines River.
- MWRD will potentially participate in a watershed group or trading program.
- A lower technology-based phosphorus effluent limit of 0.5 mg/L will be established, with compliance by 2030, if feasible—unless a lower limit is required under the implementation plan.
The Calumet O’Brien and Stickney NPDES permits were reissued on July 6, 2017. In 2015, average phosphorus removal was 93 percent (based on influent phosphorus load) at Stickney, with optimization of the system still in progress. In May of 2015, the Ostara® process went online, resulting in controlled production of phosphorus recovery in sidestream in the form of a slow-release fertilizer, magnesium ammonium phosphate. In fact, through the recovery process, 9,000–10,000 tons of fertilizer will be produced annually for Crystal Green®. This is an opportunity for a more environmentally-friendly phosphorus lifecycle.
Currently, testing of enhanced biological phosphorus removal and the Ostara® process are under way at Calumet, O’Brien, Egan, and Hanover Park facilities. Looking forward, the Stickney plant expects to complete construction of the waste-activated sludge stripping process by December 2017. This process further increases phosphorus removal.
