Ohio Wastewater Treatment Plants

Introduction

Ohio stands as a critical junction in the United States water infrastructure landscape, managing two distinct and vital watersheds: the Lake Erie basin to the north and the Ohio River basin to the south. With a highly industrialized history and significant urban density, Ohio’s wastewater infrastructure is extensive, comprising over 2,000 publicly owned treatment works (POTWs). The state is currently in a phase of massive capital reinvestment, driven largely by aging infrastructure needs and federal consent decrees aiming to eliminate Combined Sewer Overflows (CSOs).

The regulatory environment is overseen by the Ohio Environmental Protection Agency (Ohio EPA), which enforces strict National Pollutant Discharge Elimination System (NPDES) permits, particularly regarding nutrient loads (phosphorus and nitrogen) to combat harmful algal blooms in Lake Erie. Currently, the state serves a population of nearly 11.8 million, with a total treatment capacity exceeding several billion gallons per day. For consulting engineers and equipment vendors, Ohio represents one of the most active markets in the Midwest, heavily supported by the H2Ohio initiative and robust State Revolving Fund (SRF) allocations.

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Recent Developments & Projects

In the last 36 months, Ohio has seen a surge in large-scale infrastructure projects. The primary driver remains the mitigation of wet weather flows. Major metropolitan sewer districts—specifically the Northeast Ohio Regional Sewer District (NEORSD), the Metropolitan Sewer District of Greater Cincinnati (MSDGC), and the City of Columbus—are midway through multi-billion dollar Long Term Control Plans (LTCPs) mandated by federal consent decrees.

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Notable recent developments include:

• Tunnel Systems: Completion of major segments of deep tunnel systems in Columbus (OARS), Cleveland (Project Clean Lake), and Akron (OCIT) to capture combined sewage for treatment rather than overflow.
• Nutrient Removal: Aggressive implementation of phosphorus removal technologies in the Maumee River watershed to protect Lake Erie, supported by H2Ohio grants.
• Energy Neutrality: A growing trend toward thermal hydrolysis and enhanced anaerobic digestion to maximize biogas production for Combined Heat and Power (CHP) systems, as seen in recent upgrades at the Southerly Wastewater Treatment Center in Columbus.
• Funding Influx: Ohio has been a significant beneficiary of the Infrastructure Investment and Jobs Act (IIJA), utilizing these funds to address emerging contaminants like PFAS and to subsidize projects in disadvantaged communities.

Top 20 Largest Treatment Plants in Ohio

The following list ranks Ohio’s wastewater treatment facilities by design average daily flow capacity (MGD). Note that peak wet weather capacities for these plants are often significantly higher due to CSO capture requirements.

*Note: Easterly’s capacity varies by operational mode; listed is typical design flow.

Detailed Profiles of Top 5 Largest Plants

Significant Regional Facilities (Rank 6-20)

• Easterly WWTP (Cleveland): Serves the eastern suburbs and drains to Lake Erie; specialized activated sludge process.
• Akron WRF: Features a BioACT system and recently integrated the massive OCIT tunnel storage system.
• Dayton WRF: Renowned for its rapid sand filtration and large-scale recharge basins.
• Euclid WWTP: Recently completed a $100M+ complete facility replacement/upgrade.

Plants with Approved Budgets & Expansion Projects

Ohio’s wastewater sector is capitalizing on SRF loans and revenue bonds to fund massive wet weather compliance projects. Below are the most significant active capital improvement projects.

A. Major Projects Under Construction (2024-2026)

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

• MSDGC Lower Mill Creek Partial Remedy (Cincinnati):
  • Budget: ~$50-$100 Million (Phased)
  • Scope: “Smart sewer” technologies and strategic separation/storage to manage CSOs without massive new tunnels.
  • Status: Design and Adaptive Management phase.

• Akron WRF Headworks Upgrade:
  • Budget: $25 Million
  • Scope: Replacement of screening and grit removal systems to handle higher peak flows from the new tunnel.
  • Status: Design complete, bidding soon.

C. Recently Completed Major Projects (2022-2024)

• Euclid WWTP Replacement: A $110M comprehensive rebuild of the primary and secondary treatment trains, completed in 2023.
• NEORSD Doan Valley Storage Tunnel: $142M tunnel project completed in 2022 to control overflows in the University Circle area.

Regulatory & Compliance Landscape

Ohio operates under a delegated NPDES program managed by the Ohio EPA Division of Surface Water. The regulatory landscape is currently defined by two major pressures:

1. Lake Erie Nutrient Targets: Under the Great Lakes Water Quality Agreement and domestic action plans, plants in the northern watershed (Toledo, Cleveland, etc.) face stringent total phosphorus limits (often 1.0 mg/L or lower) to combat algal blooms.
2. CSO Long Term Control Plans: Virtually every major Ohio river city is under a consent decree. Regulators are increasingly open to “Integrated Planning” frameworks, allowing utilities to prioritize high-impact projects (like Green Infrastructure) over gray infrastructure if the environmental benefit is proven.

Technology Trends in Ohio

Engineering firms and vendors should note the following technology adoption trends across the state:

• Chemically Enhanced Primary Treatment (CEPT): Widely adopted in Columbus and Toledo to treat massive volumes of wet weather flow without biological upset.
• Thermal Hydrolysis (THP): Gaining traction for biosolids processing to reduce volume and increase Class A biosolid production.
• Real-Time Control (RTC): “Smart Sewer” sensors and actuated gates are being aggressively deployed in Cincinnati and South Bend (nearby) to maximize in-system storage, reducing the need for new concrete tanks.
• UV Disinfection: Rapidly replacing gaseous chlorine systems to improve safety and reduce residuals in aquatic habitats.

Complete Directory of Facilities

Browse our comprehensive directory of wastewater treatment plants in Ohio. (Select links below for full plant details).

Resources for Engineers & Operators

• Ohio Water Environment Association (OWEA): www.ohiowea.org – The primary professional association for networking and training.
• Ohio EPA Division of Surface Water: Operator certification and permitting details.
• Ohio Water Development Authority (OWDA): The primary funding arm for water infrastructure loans in the state.
• Operator Training: The Operator Training Committee of Ohio (OTCO) offers CEUs and exam prep.

FAQ

How many wastewater treatment plants are in Ohio?

Ohio has over 2,000 permitted Publicly Owned Treatment Works (POTWs), ranging from massive regional facilities to small package plants.

What is the largest wastewater treatment plant in Ohio?

The Southerly Wastewater Treatment Center in Columbus is generally considered the largest by average flow, treating over 114 MGD on average.

Which Ohio cities are under Consent Decrees for sewage?

Most major Ohio cities including Columbus, Cincinnati (MSDGC), Cleveland (NEORSD), Akron, Toledo, and Lima are operating under consent decrees to reduce Combined Sewer Overflows (CSOs).

What funding is available for WWTP upgrades in Ohio?

Funding is primarily available through the Water Pollution Control Loan Fund (WPCLF) managed by the Ohio EPA and OWDA. Additionally, H2Ohio grants are available specifically for nutrient reduction projects.

What are the nutrient removal requirements in Ohio?

Plants discharging into the Lake Erie watershed face strict phosphorus limits, often capped at 1.0 mg/L, with many facilities optimizing to reach 0.5 mg/L to prevent algal blooms.