Indiana Wastewater Treatment Plants

1. Introduction

Indiana’s wastewater infrastructure is currently undergoing one of the most significant transformation periods in the state’s history. Driven by the need to remediate Combined Sewer Overflows (CSOs) in river-adjacent cities and support the rapid suburban growth in the Indianapolis metropolitan area, the Hoosier state represents a robust market for engineering services and treatment technologies.

Regulated by the Indiana Department of Environmental Management (IDEM), the state oversees approximately 800 permitted wastewater facilities. The infrastructure landscape is dominated by the challenge of managing wet weather flows in legacy river cities like Indianapolis, Fort Wayne, Evansville, and South Bend, which are collectively investing billions in tunnel systems and storage capacity.

Currently, Indiana facilities process a total design capacity exceeding 1,400 MGD. The market is shifting from purely compliance-driven “gray infrastructure” (tunnels and concrete) toward “smart water” optimization, nutrient removal (specifically phosphorus), and energy neutrality through advanced biosolids processing.

Indiana is profiled here as part of the site’s wider directory of US wastewater treatment plants, and the state is worth studying comparatively because it produced both of the dominant answers to the combined sewer problem. Indianapolis and Fort Wayne built deep rock tunnels; South Bend instrumented its collection system and avoided most of the concrete. Utilities elsewhere choosing between those paths are increasingly working from Indiana performance data rather than from theory.

2. Recent Developments & Projects

The defining characteristic of the Indiana wastewater sector in the last three years has been the culmination of Long-Term Control Plans (LTCPs) for CSO compliance. Major metropolitan districts are nearing the completion of multi-decade consent decree timelines, shifting focus toward plant optimization and asset management.

Key developments include:

• The “DigIndy” Milestone: Citizens Energy Group is nearing the final stages of its $2 billion tunnel system, significantly reducing overflows into the White River and Fall Creek.
• Regionalization Initiatives: Smaller utilities in Central Indiana are increasingly exploring consolidation or regional treatment agreements to handle the population boom in Hamilton and Boone counties (the LEAP District).
• Advanced Biosolids: There is a statewide trend toward upgrading anaerobic digestion facilities to produce Renewable Natural Gas (RNG), led by projects in Indianapolis and West Lafayette.
• State Revolving Fund (SRF) Activity: The Indiana Finance Authority (IFA) has been aggressive in leveraging IIJA funds, offering interest rate buy-downs for projects that incorporate green infrastructure and non-point source pollution control.

3. Top 20 Largest Treatment Plants in Indiana

The following list ranks the largest wastewater treatment facilities in Indiana based on average design capacity (MGD). These facilities represent the backbone of the state’s sanitary infrastructure.

Profiles of the Top 5 Largest Plants

4. Facility Profiles & Plant Records

Indiana’s treated flow concentrates in five metropolitan systems, each of which took a distinct technical route through its consent decree. The records below cover the individual facilities documented in detail on this site, organized by operating utility.

Citizens Energy Group Belmont, Indianapolis

The Citizens Energy Group Belmont Advanced Wastewater Treatment Plant Indianapolis is rated at 120 MGD average with peak wet weather capability above 300 MGD, discharging to the White River and serving roughly 450,000 people. Its structural role in the Indianapolis system is as the solids hub: Belmont handles biosolids for both city plants, combining large-scale incineration with recently upgraded anaerobic digestion. That split-function arrangement, with Southport optimized for liquid stream and Belmont carrying the solids, is unusual at this scale and means the two plants cannot be evaluated independently. The DigIndy tunnel terminates at the Southport and Belmont complex, requiring deep rock pump stations to lift captured flow more than 200 feet to the headworks. For engineers, that lift is the defining hydraulic feature of the Indianapolis system and the single largest ongoing energy cost associated with the tunnel program.

Citizens Energy Group Southport, Indianapolis

The Citizens Energy Group Southport Advanced Wastewater Treatment Plant Indianapolis is the largest single facility in the state at 125 MGD design capacity, and it is built around a high-purity oxygen activated sludge process fed by an on-site cryogenic oxygen plant. Pure oxygen systems deliver high-rate treatment in a constrained footprint but concentrate operational risk in the oxygen generation train, where an outage has an immediate biological consequence. Sludge is pumped to Belmont through inter-plant pipelines rather than processed on site, which is why Southport’s capital program skews toward liquid stream and wet weather capacity. The plant is central to meeting the 97 percent capture rate the city’s consent decree requires. Suppliers of oxygen generation, high-rate disinfection, and wet weather clarification equipment should treat Southport as the Indiana reference installation.

Fort Wayne Water Pollution Control Plant

The Fort Wayne Water Pollution Control Plant treats up to 100 MGD for about 270,000 people, discharging to the Maumee River and, through it, to western Lake Erie. That receiving water matters: Fort Wayne is the only large Indiana system whose nutrient obligations connect directly to the Lake Erie harmful algal bloom framework rather than to Ohio River basin conditions. The plant relies on high-rate clarification and retention basins to absorb flow from the Tunnel Works deep rock project, and it operates digester gas cogeneration to offset power costs. Tunnel completion has shifted the constraint to the plant’s front end, the same pattern seen in tunnel programs across the Midwest. Engineers should read Fort Wayne as the Indiana case study in sequencing headworks capacity against storage delivery.

South Bend Wastewater Treatment Plant

The South Bend Wastewater Treatment Plant is rated at 48 MGD with a 77 MGD peak, modest by state standards, but it is the most internationally studied facility in Indiana because of what happens upstream of it. The city’s CSOnet deployment placed distributed level sensors and automated valves throughout the collection system, allowing operators to hold flow in existing pipe volume and meter it to the plant rather than overwhelming it. The reported result was roughly $400 million in avoided gray infrastructure spending against the original control plan. The engineering lesson is that most combined systems contain far more usable in-pipe storage than static design assumptions credit, and that finding it costs a fraction of building new volume. Utilities evaluating real-time control as a tunnel alternative generally start with the South Bend data set.

Evansville Wastewater Treatment System

The Evansville Wastewater Treatment Plant record covers the city’s treatment operations on the Ohio River, where the West plant carries about 30.6 MGD and the East plant roughly 18 MGD under the Evansville Water and Sewer Utility. Evansville’s Renew Evansville program is the most distinctive long-term control plan in the state because it pairs conventional pumping capacity with constructed wetland treatment, replacing the Bee Slough open sewer rather than tunneling around it. That choice reflects southern Indiana geology and floodplain conditions that make deep rock tunneling less attractive than it is in Indianapolis or Fort Wayne. Ohio River discharge also places Evansville under different downstream scrutiny than the Great Lakes basin plants. For engineers, it is the state’s leading example of a green and gray hybrid control plan at municipal scale.

5. The Indianapolis Consent Decree and DigIndy

Roughly 60 percent of Indiana’s active capital spending traces to CSO compliance, and the largest single program by a wide margin is the Indianapolis consent decree. The plant records below cover the compliance history and tunnel integration work at the two facilities that receive DigIndy flow.

Belmont Under the Consent Decree

The compliance record for the Indianapolis Belmont Advanced Wastewater Treatment Plant traces the facility’s role through the city’s long-term control plan, from the original overflow reduction obligations to the current tunnel integration phase. Belmont’s exposure is unusual because it carries both a liquid stream obligation and the solids consequences of every gallon the tunnel captures: flow that once overflowed to the White River now arrives at the plant carrying its full solids load. That shift raised the throughput requirement on incineration and digestion well beyond what the original consent decree analysis anticipated for the solids train. Utilities planning tunnel programs elsewhere frequently underestimate this second-order effect, budgeting for hydraulic capacity while leaving solids handling at pre-tunnel design.

Southport and the 97 Percent Capture Requirement

The record for the Indianapolis Southport Advanced Wastewater Treatment Plant covers the plant’s compliance obligations under the same decree, principally the 97 percent wet weather capture rate the city must demonstrate. Meeting a capture percentage rather than an overflow count changes the engineering problem: performance is measured across a typical year of rainfall, so the design must handle the accumulated small and medium storms rather than one design event. Southport’s high-rate treatment capacity and its ability to accept dewatered tunnel flow over an extended period after each storm are what make the percentage achievable. The extended post-storm dewatering period, rather than the storm peak itself, is the sustained load condition that governs the plant’s wet weather design.

6. Plants with Approved Budgets & Expansion Projects

Indiana currently has over $2.5 billion in active water infrastructure projects, driven largely by Consent Decrees and the federal IIJA funding influx.

A. Major Projects Under Construction (2024-2026)

B. Projects in Design/Planning Phase (2025-2027)

• Carmel Utilities WWTP Expansion:
  Budget: ~$40-50 Million
  Scope: Expansion of treatment capacity to accommodate rapid population growth in Hamilton County. Includes nutrient removal upgrades.
  Status: Design/Permitting.
• City of Fishers – AgriPark & Reuse Initiative:
  Budget: TBD
  Scope: Evaluation of water reuse technologies to support local agriculture and green space, reducing discharge to receiving streams.
• Jeffersonville Wastewater Capacity Upgrade:
  Budget: $22 Million
  Scope: Expansion of the North Plant to handle industrial growth at the River Ridge Commerce Center.
  Funding: Local Revenue Bonds/SRF.

Summary Statistics

• Total Active Capital Investment: ~$2.5 Billion (Statewide active construction)
• Primary Project Drivers: CSO Compliance (60%), Growth/Capacity (25%), Aging Asset Replacement (15%).
• Funding Source Breakdown:
  • State Revolving Fund (SRF): 45%
  • WIFIA/Federal Loans: 30%
  • Revenue Bonds: 20%
  • IIJA Grants: 5%

7. Regulatory & Compliance Landscape

The Indiana Department of Environmental Management (IDEM) enforces the National Pollutant Discharge Elimination System (NPDES) in the state. The regulatory environment is currently defined by three major factors:

1. CSO Long-Term Control Plans (LTCPs): Indiana has over 100 communities with Combined Sewer Overflows. Most are in the final stages of implementing their 20-year control plans (gray infrastructure tunnels and storage).
2. Phosphorus Limits: IDEM is progressively tightening total phosphorus limits to 1.0 mg/L or lower for major municipal dischargers to combat algae blooms in the Great Lakes and Ohio River basin.
3. PFAS Monitoring: IDEM has completed Phase 1-3 testing of community water systems and is moving toward testing wastewater effluent and biosolids. While strict effluent limits are not yet set, utilities are preparing for future regulations regarding “forever chemicals.”

Two Basins, Two Nutrient Regimes

Indiana straddles a watershed divide that has more practical effect on permit writing than most engineers expect. Northern systems, principally Fort Wayne on the Maumee and the Lake Michigan basin plants in Lake and Porter counties, sit within Great Lakes nutrient frameworks driven by harmful algal blooms in western Lake Erie and nearshore Lake Michigan. Everything from Indianapolis south drains eventually to the Ohio and Mississippi, where the driver is Gulf hypoxia and, unlike the Chesapeake, there is no enforceable interstate load allocation. The consequence is that phosphorus limits arrive facility by facility through permit renewals and antidegradation review rather than through a single statewide cap. Utilities planning expansions should expect nutrient conditions to be negotiated as part of the permit modification, and should budget the schedule for that conversation.

The Small-Community Compliance Gap

Roughly 800 permitted facilities exist statewide, but the large plants profiled above represent a small fraction of that count. The long tail is small municipal plants and lagoons serving communities of a few thousand or fewer, many of which face ammonia and phosphorus limits their existing processes cannot meet. IIJA and SRF interest rate buy-downs have made a wave of these upgrades viable, and the Indiana Finance Authority’s willingness to favor projects incorporating green infrastructure has shaped what gets proposed. The realistic outcomes for these systems are package mechanical plants, lagoon upgrades with added treatment units, or regionalization with a neighboring utility. Consulting engineers serving this market should expect alternatives analyses comparing all three to remain steady work.

8. Infrastructure Challenges & Opportunities

Aging Collection Systems: Beyond the headline-grabbing tunnel projects, Indiana faces a quiet crisis in small-town collection systems. Inflow and Infiltration (I/I) plague older communities, causing hydraulic overloads at plants even without CSOs.

Workforce Shortages: Like many states, Indiana faces a “Silver Tsunami” of retiring Class III and IV operators. This is driving demand for automation, SCADA upgrades, and contract operations services.

Industrial Pretreatment: Indiana is a manufacturing-heavy state (automotive, steel, pharmaceuticals). Publicly Owned Treatment Works (POTWs) must maintain rigorous Industrial Pretreatment Programs (IPP) to prevent upset conditions, creating opportunities for consulting engineers specialized in industrial waste.

9. Technology Trends in Indiana

• Real-Time Control (RTC): Following South Bend’s success, more utilities are adopting “Digital Twin” technology and AI-driven sensor networks to optimize collection system storage before building new concrete tanks.
• Biological Phosphorus Removal (EBPR): To meet new nutrient limits without high chemical costs, plants are retrofitting aeration basins for biological phosphorus removal.
• UV Disinfection: A rapid shift away from gaseous chlorine to UV disinfection systems to improve safety and reduce chemical handling requirements.
• Thermal Hydrolysis: Citizens Energy Group’s implementation of thermal hydrolysis (Cambi process) represents the cutting edge of biosolids management in the Midwest, allowing for higher Class A biosolids production and energy recovery.

10. Directory of Facilities

Browse our organized directory of wastewater treatment plants in Indiana:

Full plant records for the facilities documented on this site are linked in the facility profiles and Indianapolis consent decree sections above, organized by operating utility.

Major Regional Facilities (>50 MGD)

• Belmont Advanced Wastewater Treatment Plant (Indianapolis)
• Southport Advanced Wastewater Treatment Plant (Indianapolis)
• Fort Wayne Water Pollution Control Plant
• Gary Sanitary District WWTP

Large Municipal Plants (20-50 MGD)

• South Bend WWTP
• Evansville West WWTP
• Hammond Sanitary District
• Terre Haute WWTP
• Muncie Water Pollution Control
• Lafayette Renew
• Carmel Utilities WWTP

Significant Community Plants (10-20 MGD)

• Elkhart WWTP
• Columbus WWTP
• Richmond Sanitary District
• Jeffersonville North WWTP
• Kokomo WWTP

11. Resources for Engineers & Operators

• Indiana Water Environment Association (IWEA): The primary professional organization for wastewater professionals in the state, offering annual conferences and technical training.
• IDEM Operator Certification: Official portal for exam scheduling, license renewal, and continuing education (CEU) requirements.
• Indiana Finance Authority – SRF: Information on State Revolving Fund loans, intended use plans (IUP), and funding cycles for infrastructure projects.
• Indiana Utility Regulatory Commission (IURC): Oversight body for utility rates and regulations.

12. Frequently Asked Questions (FAQ)

What is the largest wastewater treatment plant in Indiana?

The largest distinct facility is the Southport Advanced Wastewater Treatment Plant in Indianapolis, with a design capacity of 125 MGD, closely followed by its sister plant, Belmont (120 MGD).

How many wastewater treatment plants are in Indiana?

There are approximately 800 permitted wastewater treatment facilities in Indiana, ranging from large municipal plants to small package plants for schools and mobile home parks.

What is the “DigIndy” project?

DigIndy is a $2 billion deep rock tunnel system in Indianapolis designed to store over 250 million gallons of combined sewage during rain events, preventing overflows into local waterways. It is one of the largest infrastructure projects in state history.

What funding is available for Indiana wastewater projects?

The primary funding source is the State Revolving Fund (SRF), managed by the Indiana Finance Authority. Recent federal IIJA grants and WIFIA loans are also major sources for large-scale capital improvements.

Are Indiana plants required to remove phosphorus?

Yes, IDEM is increasingly including phosphorus limits (typically 1.0 mg/L) in NPDES permits for major municipal dischargers to protect downstream water quality.

What are the operator certification levels in Indiana?

Indiana classifies municipal wastewater operators from Class I (smallest plants) to Class IV (largest, most complex plants). Industrial operators utilize classifications A through D.

How is Indiana addressing PFAS in wastewater?

IDEM has initiated a sampling program for PFAS in community water systems and is currently developing strategies for testing wastewater effluent and biosolids, though strict numerical limits have not yet been universally adopted in permits.

Why do Indianapolis and South Bend have such different control plans?

Indianapolis committed to gray infrastructure, building the 28-mile DigIndy tunnel network to store 250 million gallons and route it to the Southport and Belmont plants. South Bend instrumented its existing collection system with distributed sensors and automated valves, using in-pipe storage that static design assumptions had never credited. South Bend’s approach reportedly avoided about $400 million in construction. Scale and system geometry explain most of the difference: Indianapolis had an overflow volume no amount of in-pipe optimization could absorb, while South Bend did not.

Which Indiana plants discharge to the Great Lakes basin?

Fort Wayne discharges to the Maumee River, which flows to western Lake Erie, and the Lake and Porter county systems including Gary and Hammond discharge into the Lake Michigan basin. These facilities face nutrient expectations tied to Great Lakes algal bloom frameworks. Plants from Indianapolis south drain toward the Ohio and Mississippi, where the nutrient driver is Gulf hypoxia and there is no enforceable interstate allocation.

How does tunnel construction affect a treatment plant’s solids handling?

Substantially, and it is routinely underestimated. Flow that formerly overflowed carried its solids load with it; once a tunnel captures that flow, those solids arrive at the plant. Thickening, dewatering, and digestion or incineration capacity all have to grow with the capture rate. Belmont’s role as the centralized solids facility for both Indianapolis plants makes this effect especially visible there.

13. Related Topics

Indiana’s control plan strategies and nutrient obligations are best understood against its neighbors. Directly east, Ohio wastewater treatment plants face a near-identical mix of large-district tunnel programs and Ohio River basin discharges, making Ohio the closest structural peer. To the west, Illinois wastewater treatment plants include the Chicago deep tunnel and reservoir system that served as the original template DigIndy and Fort Wayne’s Tunnel Works were measured against. Across the Ohio River, Kentucky wastewater treatment plants share the receiving water for southern Indiana discharges including Evansville, and face comparable combined sewer obligations in the Louisville and Cincinnati metro areas.

14. Conclusion

Indiana is a market in transition. The consent decree era that defined the past two decades is ending, with DigIndy and Tunnel Works both approaching completion, and the spending that follows will look different: plant optimization, nutrient retrofits, solids and energy recovery, and a long queue of small-community upgrades riding federal funding cycles. The state’s $2.5 billion in active work is the tail end of one program and the beginning of another.

For engineers, operators, and suppliers, the useful framing is to establish which of three markets a project sits in before scoping it: metropolitan consent decree work with its heavy civil and deep pump station procurement, mid-sized municipal upgrades driven by phosphorus limits and suburban growth in the Indianapolis collar counties, or small-community projects funded through SRF and IIJA cycles. Each has a different buyer, funding route, and technology fit. The facility and compliance records linked throughout this guide are the starting point for placing a project correctly.