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Photo courtesy Metropolitan Water Reclamation District of Greater Chicago
On Friday, July 17, the Metropolitan Water Reclamation District (MWRD) launched the new disinfection facility at the Calumet Wastewater Treatment Plant on Chicago’s far south side, adding a final step to the sewage treatment process that will kill more of the bacteria and other pathogens still present in the wastewater before it is discharged into the Little Calumet River. Four years after the MWRD Board of Commissioners voted to support installing disinfection facilities at two of the largest plants and a full seven months ahead of the original deadline, the start of disinfection at the Calumet plant is a signal achievement — heralded by Illinois' Senator Dick Durbin and US EPA Region 5 Administrator Susan Hedman, among others.
Using an existing chlorine contact chamber retrofitted for more efficient contact, the disinfection technology neutralizes or kills bacteria and microorganisms in treated water. Engineers modified the existing chlorine contact basin by replacing all interior baffle walls and associated walkways; replacing weir gates, discharge gates, drain sluice gates, inlet sluice gates and a bypass sluice gate; replacing liquid sodium hypochlorite diffuser piping; installing liquid sodium bisulfite diffuser piping; and installing sampling pumps. The chlorine is neutralized after killing the bacteria so that no harmful byproducts are discharged into the waterways.
In operation since 1922, the Calumet plant is the oldest of the seven MWRD plants in operation. The plant, which has 268 employees, treats an average 354 million gallons of wastewater per day and a maximum 430 million gallons per day, serving more than one million people in an area of more than 300 square miles.
Margaret Frisbie, executive director of Friends of the Chicago River, hailed the launch of disinfection as a milestone. “Not only are we achieving a new benchmark in water quality,” she said at the ribbon-cutting ceremony, “we are also investing in the health of our communities by improving quality of life and access to the river for recreation and exercise while creating business income and jobs.”