South Bend Wastewater Treatment Plant

FACILITY BASIC INFORMATION

Plant Name: South Bend Wastewater Treatment Plant

Location: 3113 Riverside Drive, South Bend, St. Joseph County, Indiana

Operating Authority: City of South Bend Department of Public Works (Utilities)

Design Capacity: 77 MGD (Secondary Treatment Capacity), Peak Hydraulic >100 MGD

Current Average Flow: ~35-48 MGD

Population Served: ~150,000 (City of South Bend, Notre Dame, regional partners)

Service Area: City of South Bend, University of Notre Dame, Roseland, and portions of St. Joseph County

Receiving Water Body: St. Joseph River

NPDES Permit Number: IN0024520

Read more4D-Printed Smart Materials For Water Treatment

Year Commissioned: 1956 (Major expansions in 1980s, 2010s)

The South Bend Wastewater Treatment Plant (WWTP) serves as the cornerstone of water quality protection for the St. Joseph River basin in Northern Indiana. Operated by the City of South Bend Department of Public Works, this advanced secondary treatment facility manages an average daily flow of approximately 48 million gallons per day (MGD) for a service population exceeding 150,000 residents, including the University of Notre Dame.

While the physical plant is a robust example of conventional activated sludge treatment, the facility is globally renowned for its integration with the city’s “Smart Sewer” network. South Bend pioneered the use of distributed sensor technology (EmNet/Xylem) to optimize collection system storage, saving the municipality hundreds of millions of dollars in unnecessary grey infrastructure costs while drastically reducing Combined Sewer Overflows (CSOs). Commissioned originally in 1956, the plant has recently undergone significant modernization, including a state-of-the-art biosolids drying facility and energy efficiency upgrades, positioning it as a leader in both digital utility transformation and environmental stewardship.

Facility Overview

A. Service Area & Coverage

The South Bend WWTP services a diverse metropolitan area encompassing the City of South Bend, the town of Roseland, the University of Notre Dame, and unincorporated areas of St. Joseph County. The collection system is a hybrid network, with approximately 500 miles of sewers. Crucially, a significant portion of the older city core utilizes a Combined Sewer System (CSS), which conveys both sanitary flow and stormwater to the plant. This creates significant hydraulic variability during wet weather events, necessitating complex flow management strategies to prevent untreated discharge into the St. Joseph River.

B. Operational Capacity

The facility is designed with a sustained secondary treatment capacity of 77 MGD. However, peak hydraulic capacity through the headworks and primary treatment exceeds 100 MGD to handle wet weather surges. Historical flow trends show an average dry weather flow of roughly 35 MGD, spiking significantly during precipitation events. The plant utilizes a specialized Wet Weather Treatment Facility (WWTF) protocol, where flows exceeding secondary capacity are routed through primary treatment and auxiliary disinfection before blending, adhering to IDEM guidelines for CSO communities.

C. Discharge & Compliance

Treated effluent is discharged directly into the St. Joseph River. The facility operates under a National Pollutant Discharge Elimination System (NPDES) permit issued by the Indiana Department of Environmental Management (IDEM). The plant is the focal point of a renegotiated Long Term Control Plan (LTCP) aimed at reducing E. coli and nutrient loading in the river. Through the implementation of smart valve technology and plant upgrades, the utility has reduced overflow volumes by over 75%, aiming for fewer than four overflow events per typical year upon LTCP completion.

Treatment Process

The South Bend WWTP employs a conventional activated sludge process supplemented by anaerobic digestion and advanced biosolids processing. The treatment train is designed to handle high-strength influent and variable hydraulic loading.

A. Preliminary Treatment

Read moreA Comparison Between Aerobic And Anaerobic Wastewater Treatment Technology

Raw wastewater enters the facility via the Main Interceptor. Preliminary treatment includes:

• Coarse Screening: Mechanically cleaned bar screens remove large debris (rags, wood, plastics) to protect downstream pumps.
• Grit Removal: Aerated grit chambers decrease the velocity of the wastewater, allowing heavier inorganic materials (sand, gravel, eggshells) to settle while keeping organic matter in suspension.
• Flow Monitoring: Magnetic flow meters and ultrasonic level sensors integrate with the SCADA system to determine real-time loading rates.

B. Primary Treatment

Flow enters rectangular primary clarifiers equipped with chain-and-flight sludge collectors.

• Process: Gravity settling removes approximately 60-70% of Total Suspended Solids (TSS) and 30-40% of Biochemical Oxygen Demand (BOD).
• Scum Removal: Surface skimmers remove grease, oils, and floatables.
• Wet Weather Mode: During extreme storm events, flows exceeding secondary capacity (above ~77 MGD) may receive primary treatment and disinfection before being discharged/blended, utilizing the Chemically Enhanced Primary Treatment (CEPT) principles when necessary.

C. Secondary Treatment

The biological heart of the plant utilizes a conventional activated sludge system.

• Aeration Basins: The plant operates multiple parallel aeration tanks. These basins use fine-bubble diffusion (upgraded from coarse bubble/mechanical in recent years) to transfer oxygen to the biomass.
• Biological Process: Microorganisms consume dissolved organic matter and ammonia. The system is operated to achieve nitrification (conversion of ammonia to nitrate).
• Secondary Clarifiers: Mixed liquor flows to circular secondary clarifiers where biological floc settles. Clear supernatant flows over the weirs to disinfection.
• RAS/WAS: Return Activated Sludge is pumped back to the head of the aeration basins; Waste Activated Sludge is thickened and sent to digestion.

D. Disinfection

Historically a chlorination/dechlorination facility, South Bend has transitioned toward Ultraviolet (UV) disinfection to eliminate the safety hazards associated with chlorine gas and reduce chemical byproducts in the St. Joseph River. The UV system is designed to meet strict E. coli limits (typically < 125 CFU/100mL monthly average) during the recreation season (April 1 – October 31).

E. Solids Handling (Biosolids)

South Bend utilizes a robust solids management program:

• Thickening: Gravity belt thickeners concentrate WAS prior to digestion.
• Anaerobic Digestion: Primary sludge and thickened WAS are stabilized in mesophilic anaerobic digesters. This process reduces pathogen content, reduces volatile solids, and generates methane gas (biogas).
• Dewatering: Digested sludge is dewatered using high-performance centrifuges.
• Thermal Drying: In a major recent upgrade, the plant installed a biosolids drying facility. This system uses thermal energy to dry dewatered cake into Class A biosolids (granules), which can be marketed as a fertilizer or soil amendment, diverting tons of material from landfills.

Infrastructure & Facilities

A. Physical Plant & Sensor Network

The site spans extensive acreage along the riverbank. Beyond the concrete treatment structures, the facility houses the central control room for the city’s celebrated “Smart Sewer” system. This distributed network of over 150 smart sensors and actuated valves in the collection system is controlled via cloud-based algorithms to maximize in-pipe storage during storms, effectively treating the collection system as an extension of the plant’s wet weather capacity.

B. Energy Systems

Energy efficiency is a primary operational driver. The plant utilizes Combined Heat and Power (CHP) technology. Biogas produced in the anaerobic digesters is captured and scrubbed to fuel cogeneration engines or boilers, providing heat for the digestion process and the thermal dryer, as well as offsetting electrical grid consumption. Recent upgrades to aeration blowers (turbo blowers) have further reduced the facility’s carbon footprint.

C. Odor Control

Given the proximity to residential areas and the river, odor control is critical. The headworks and new biosolids drying facility are equipped with negative pressure containment and chemical scrubbers/biofilters to treat foul air before release.

Recent Upgrades & Major Projects

South Bend has been in a continuous state of improvement to meet the requirements of its Consent Decree and LTCP.

Biosolids Management Facility (2018-2020)

• Project Scope: Construction of a new thermal drying facility to convert Class B cake into Class A granular biosolids.
• Budget: ~$13 Million (Estimated).
• Drivers: Limited landfill capacity, rising disposal costs, and sustainability goals.
• Technology: Thermal drying drum system utilizing biogas and natural gas.
• Result: production of a marketable fertilizer product, reduction in trucking volume/costs, and beneficial reuse of waste.

“Reimagined” Long Term Control Plan (Ongoing)

• Project Scope: A shift from massive grey infrastructure (deep tunnels) to smart technology and targeted improvements.
• Budget: Total LTCP savings estimated at ~$400 Million compared to original baseline.
• Technical Highlights: Implementation of real-time decision support systems (EmNet/Xylem BLU-X).
• Result: The smart sewer implementation reduced dry weather overflows to near zero and reduced wet weather overflow volume by ~70-80% immediately upon implementation, virtually eliminating the need for certain proposed storage tanks.

Aeration System Improvements (2016-2018)

• Scope: Replacement of aging blowers and diffusers.
• Technology: Installation of high-efficiency turbo blowers and fine pore membrane diffusers.
• Result: Significant reduction in electrical consumption (aeration typically accounts for 50-60% of a plant’s energy use) and improved dissolved oxygen control.

Regulatory Compliance & Environmental Performance

A. Permit Requirements

The facility operates under NPDES Permit IN0024520. Key discharge limits include:

• CBOD5: Monthly average limits typically around 25 mg/L (summer) / 40 mg/L (winter).
• TSS: Monthly average limits typically 30 mg/L (summer) / 45 mg/L (winter).
• Ammonia-Nitrogen: Seasonal limits to prevent toxicity to aquatic life (often < 2-3 mg/L in summer).
• Phosphorus: 1.0 mg/L monthly average.
• E. Coli: 125 CFU/100ml geometric mean (April-October).

B. CSO Consent Decree

South Bend is a national case study for renegotiating federal Consent Decrees based on “Smart” technology. Originally mandated to build extensive deep tunnels, the City demonstrated that optimizing the existing system via sensors and logic control could achieve better environmental outcomes faster and cheaper. This “Smart Sewer” approach was accepted by the DOJ and EPA, setting a precedent for other utilities.

Operational Excellence

Staffing: The plant is staffed by a team of state-certified wastewater operators (Class I through Class IV), industrial electricians, millwrights, and laboratory technicians. The facility operates 24/7/365.

Innovation: The integration of Artificial Intelligence (AI) into the conveyance system distinguishes South Bend. The system predicts rainfall and automatically adjusts gates and valves to store water in the largest pipes, smoothing the hydraulic peak hitting the plant and maximizing treatment volume.

Challenges & Future Planning

Aging Infrastructure: While the “smart” layer is modern, concrete assets from the 1950s and 1980s require structural rehabilitation. Capital improvement plans focus heavily on asset management and rehabilitation of primary clarifiers and interceptor linings.

Nutrient Limits: Like many Midwest utilities, South Bend faces tightening regulations regarding nutrient loading (Nitrogen and Phosphorus) to the Mississippi River basin. Future phases may require enhanced Biological Nutrient Removal (BNR) configurations.

Technical Specifications Summary

Frequently Asked Questions

Technical Questions

1. What is the peak wet weather capacity of the South Bend WWTP?
   The plant can hydraulically pass over 100 MGD through primary treatment. Secondary biological treatment is generally rated for 77 MGD; flows exceeding this may receive primary treatment and disinfection before blending.
2. How does the “Smart Sewer” system affect the plant?
   The sensor network optimizes in-system storage, flattening the peak flow curve that hits the plant. This prevents the plant from being overwhelmed instantly during storms, allowing for a more consistent treatment rate and reducing bypasses.
3. Does South Bend utilize Biological Nutrient Removal (BNR)?
   The plant utilizes chemical precipitation (typically Ferric Chloride or Alum) for phosphorus removal and operates aeration zones to achieve nitrification (ammonia removal). Full biological denitrification/phosphorus removal is a focus of ongoing optimization.
4. What happens to the biosolids produced?
   Solids are anaerobically digested and then thermally dried in the new Biosolids Management Facility to create a Class A fertilizer product, or dewatered and land applied as Class B biosolids depending on operational mode.

Public Interest Questions

1. How many people does the plant serve?
   The facility serves a regional population of approximately 150,000 people, including South Bend, Notre Dame, and surrounding areas.
2. Does the plant smell?
   While wastewater treatment inherently generates odors, South Bend utilizes anaerobic digestion (enclosed) and has installed chemical scrubbers and biofilters at key locations (headworks, solids handling) to minimize off-site odors.
3. Is the water released into the river clean?
   Yes. The effluent must meet strict state and federal standards for clarity, bacteria, and oxygen-demanding substances. It is generally cleaner than the river water itself.