Tennessee Wastewater Treatment Plants

1. Introduction

Tennessee’s wastewater infrastructure landscape is currently undergoing its most significant transformation in decades, driven by rapid population growth in the Nashville-Murfreesboro corridor and massive consent decree-driven overhauls in Memphis, Chattanooga, and Nashville. The state operates under the regulatory oversight of the Tennessee Department of Environment and Conservation (TDEC), managing a network of over 260 public municipal wastewater treatment plants (WWTPs).

Currently, Tennessee facilities treat approximately 1.2 billion gallons of wastewater daily. The state faces a unique hydrological divide: West Tennessee facilities primarily discharge into the high-volume Mississippi River, allowing for different effluent limits compared to Middle and East Tennessee plants, which discharge into sensitive tributaries of the Cumberland and Tennessee Rivers. This dichotomy creates distinct engineering challenges, ranging from nutrient removal requirements in the east to massive hydraulic capacity needs in the west.

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With the recent influx of American Rescue Plan (ARP) funds managed through the Tennessee Water Infrastructure Investment Plan (TWIIP), the state has allocated over $1.35 billion in grants, spurring a construction boom for consulting engineers and equipment vendors alike.

2. Recent Developments & Projects

The wastewater sector in Tennessee is currently defined by the convergence of federal funding and regulatory enforcement. In the last 24 months, the state has moved aggressively to address aging infrastructure that contributes to sanitary sewer overflows (SSOs).

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Key developments include:

• TDEC ARP Grants: In late 2022 and throughout 2023, TDEC awarded over $1 billion in non-competitive grants to cities and counties for water infrastructure, requiring local matches that have mobilized nearly $2 billion in total capital activity.
• Memphis Consent Decree Work: The City of Memphis is midway through a $250 million update to its major plants to address EPA compliance, focusing on disinfection and biosolids.
• Regionalization Studies: TDEC is actively funding engineering studies to assess the viability of connecting struggling small utility districts to larger, more capable municipal systems, creating opportunities for pipeline and pump station engineering projects.
• Biosolids Innovation: Chattanooga continues to lead with its thermal hydrolysis process (THP) installation, setting a precedent for energy neutrality in the region.

3. Top 20 Largest Treatment Plants in Tennessee

The following table ranks Tennessee’s largest wastewater treatment facilities by Design Capacity (MGD). Data is aggregated from TDEC NPDES permits, EPA ECHO database, and municipal Capital Improvement Plans (CIP).

*Note: Moccasin Bend’s capacity fluctuates based on wet weather protocols; peak hydraulic capacity is significantly higher.

Detailed Profiles of the Top 5 Largest Plants

4. Plants with Approved Budgets & Expansion Projects

Tennessee is currently seeing a surge in capital expenditure, primarily funded by State Revolving Funds (SRF), Revenue Bonds, and the TDEC-administered ARP grants. The following projects represent the most significant engineering opportunities in the state.

A. Major Projects Under Construction (2024-2026)

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

• Smyrna WWTP Expansion Phase 3: Design phase for increasing capacity from 15.85 MGD to 22.5 MGD. Estimated Budget: $45 Million. Driver: Regional automotive and residential growth.
• Harpeth Valley Utility District Expansion: Planning stages to expand treatment capacity to accommodate western Davidson/Williamson County growth. Budget: ~$30 Million.
• Clarksville WWTP Biosolids Upgrade: Engineering design for improved solids handling and thermal drying. Estimated Budget: $20 Million.

C. Summary Statistics

5. Regulatory & Compliance Landscape

The Tennessee Department of Environment and Conservation (TDEC) Division of Water Resources enforces the state’s water quality standards. Tennessee operates under delegated NPDES authority from the EPA.

• Nutrient Reduction: TDEC has been tightening limits on Nitrogen and Phosphorus, particularly for plants discharging into the Tennessee River watershed, necessitating upgrades to Biological Nutrient Removal (BNR) processes.
• Consent Decrees: Nashville, Memphis, Chattanooga, and Knoxville have all operated under federal consent decrees, which mandate strict schedules for reducing Sanitary Sewer Overflows (SSOs). This is the primary legal driver for the billion-dollar investments seen in these metro areas.
• PFAS Monitoring: TDEC has initiated statewide sampling for PFAS in wastewater effluent. While strict limits are not yet in all permits, engineers should anticipate future PFAS treatment requirements in design phases.

6. Infrastructure Challenges & Opportunities

Inflow and Infiltration (I&I): The geology of Tennessee (karst terrain in the middle/east) combined with aging clay pipes results in massive I&I issues. During heavy rain events, plants like Nashville’s Central or Chattanooga’s Moccasin Bend see flow spikes of 300-400% above average. This creates a robust market for sewer rehabilitation, lining, and flow equalization basin construction.

Workforce Shortage: Tennessee faces a critical shortage of certified Grade 3 and 4 operators. Automation and SCADA upgrades are increasingly viewed not just as efficiency tools, but as necessary adaptations to a shrinking workforce.

7. Technology Trends in Tennessee

• Disinfection Evolution: A rapid move away from chlorine gas due to safety concerns. Large plants are moving to UV (Nashville, Memphis Stiles) or Peracetic Acid (Memphis Maxson pilots).
• Thermal Hydrolysis: Chattanooga’s adoption of CAMBI technology has set a regional standard for high-efficiency biosolids processing, generating class A biosolid fertilizer.
• Decentralized Treatment: In rapid-growth areas like Williamson County, decentralized STEP (Septic Tank Effluent Pumping) systems and small satellite plants are being used to bypass the lag time of massive central sewer expansion.

8. Directory of Facilities

Browse our comprehensive directory of wastewater treatment plants in Tennessee:

• M.C. Stiles WWTP (Memphis)
• Central WWTP (Nashville)
• Moccasin Bend WWTP (Chattanooga)
• Kuwahee WWTP (Knoxville)
• Dry Creek WWTP (Nashville)
• Murfreesboro WRRF

9. Resources for Engineers & Operators

• Tennessee Department of Environment and Conservation (TDEC): Regulatory guidance and SRF funding information.
• Clean Water Professionals of Kentucky & Tennessee (CWP-KT): The primary Water Environment Federation (WEF) member association for the region.
• Tennessee Association of Utility Districts (TAUD): Provides training and certification for operators.
• Fleming Training Center: The state’s hub for operator licensure exams and classes.

10. FAQ Section

How many wastewater treatment plants are in Tennessee?

Tennessee has approximately 260 public municipal wastewater treatment plants, in addition to numerous industrial and private decentralized systems.

What is the largest wastewater treatment plant in Tennessee?

The M.C. Stiles Wastewater Treatment Plant in Memphis is the largest by design flow, with a capacity of 135 MGD, though Chattanooga’s Moccasin Bend handles higher wet-weather peak flows.

What funding is available for WWTP upgrades in Tennessee?

The primary funding vehicles are the State Revolving Fund (SRF) loans and the TDEC-administered American Rescue Plan (ARP) grants, which recently allocated $1.35 billion for water infrastructure.

Are Tennessee plants required to remove nutrients?

Yes, plants discharging into nutrient-impaired waters (common in East and Middle Tennessee) generally have strict Nitrogen and Phosphorus limits in their NPDES permits.

Who regulates wastewater treatment in Tennessee?

The Tennessee Department of Environment and Conservation (TDEC), specifically the Division of Water Resources.