The South Bend Wastewater Treatment Plant is a Class IV activated sludge treatment facility with an average design flow of 48.0 MGD (Million Gallons per Day) and a peak design flow of 77.0 MGD, discharging to the St. Joseph River. Treatment units include:
- 3 Mechanical Fine Bar Screens
- 2 Grit Removal Tanks
- 8 Primary Clarifiers
- 4 Aeration Tanks
- 7 Final Clarifiers
- Solids Thickening Tank
- 3 Dissolved Air Floatation Units
- Sludge Blending Tank
- 4 Anaerobic Digesters
- 4 Belt Filter Presses
The South Bend sewage collection system consists of over 590 miles of sanitary and combined sewers, and over 40 pumping stations. There are 36 combined sewer overflow locations along the St. Joseph River where combined sewage may be discharged during wet weather.
Pumping stations and combined sewer overflow points are monitored continuously to ensure proper operation. Alarms are triggered at the wastewater treatment plant, and crews are dispatched to respond to any problems that may be detected.
Continuous monitoring at the combined sewer overflow points allows the City to proactively address any problems within the system that may lead to increased overflows.
The City of South Bend is currently implementing elements of a Long Term Control Plan to reduce the amount of combined sewage that is discharged.
The South Bend Wastewater Treatment plant serves the City of South Bend and surrounding areas. The plant is staffed 24 hours per day, and an electronic SCADA system is used to continuously monitor processes and equipment.
As wastewater enters the plant, large debris is removed by the mechanical fine bar screens.
Wastewater flow is slowed in two grit tanks to allow sand, grit and stones to settle out. This material is disposed of at a solid waste landfill.
In eight primary clarifiers, the wastewater flow is slowed even more. Finer solids settle to the bottom, and this sludge is removed and treated in the solids handling process. Fats, oils, and grease rise to the top of the primary clarifiers and this material is skimmed off and disposed of at a solid waste landfill.
After primary treatment, the wastewater moves on to biological treatment in four aeration tanks. Compressed air is introduced to allow aerobic bacteria to further reduce dissolved pollutants. Ammonia is converted using step feed single stage nitrification. Phosphorus is removed via biological uptake with supplemental chemical addition, when needed.
From the aeration tanks, the flow goes into seven secondary clarifiers where the activated sludge mass settled out and returned to the aeration tanks, or sent to the solids handling process.
The water leaving the secondary clarifiers goes on to be disinfected. Ton cylinders are used to introduce chlorine gas into the secondary effluent. Sulfur dioxide is added to remove the chlorine before the water is discharged to the St. Joseph River.
Solids removed from the wastewater treatment process are concentrated in a primary sludge thickening tank, three dissolved air floatation units, and a sludge blending tank. Solids are treated in two primary and two secondary anaerobic digesters.
Solids are dewatered to approximately 18% solids using four belt filter presses. The sludge, or biosolids, is then stored at the South Bend Organic Resources Facility. Sludge is beneficially reused on farm land through a land application program. The Organic Resources Facility operates the land application program, and also produces a compost material year round from yard and other vegetative waste.