The District owns and operates a main treatment plant, an excess flow treatment facility, a wet weather retention facility, a biosolids storage facility, three lift stations and approximately 14 miles of large-diameter trunk and interceptor sewers.
At the main treatment plant during dry weather flow conditions, all wastewater receives preliminary treatment, primary treatment, secondary (activated sludge) treatment, tertiary (sand filtration) treatment and disinfection prior to discharge.
The District’s peak treatment and storage flow rate capacity is 140 million gallons per day. During wet weather flow conditions, the District may utilize its 26-mgd excess flow treatment facility (in the Village of Homewood) and/or its 35 million gallon wet weather retention facility (in the City of Chicago Heights).
At the main treatment plant during wet weather flow is reached, once the capacity of the secondary treatment process is reached, additional water is stored in the empty excess flow primary clarifiers. If the excess flow primary clarifiers are filled and flows continue to exceed secondary treatment capacity, additional flows up to 50.25 mgd receive preliminary treatment, primary treatment, tertiary treatment and disinfection. Flows above 50.25 receive preliminary treatment, primary treatment and disinfection. All discharge from the treatment plant meets secondary treatment requirements.