Tennessee Wastewater Treatment Plants

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).

Rank Plant Name City/Location Design Capacity (MGD) Population Served Operating Authority
1 M.C. Stiles WWTP Memphis 135.0 MGD 650,000 City of Memphis
2 Moccasin Bend WWTP Chattanooga 140.0 MGD* 400,000 City of Chattanooga
3 Central WWTP Nashville 100.0 MGD 350,000 Metro Water Services
4 T.E. Maxson WWTP Memphis 80.0 MGD 300,000 City of Memphis
5 Kuwahee WWTP Knoxville 44.0 MGD 160,000 Knoxville Utilities Board (KUB)
6 Dry Creek WWTP Nashville 24.0 MGD 145,000 Metro Water Services
7 Whites Creek WWTP Nashville 37.5 MGD 120,000 Metro Water Services
8 Fourth Creek WWTP Knoxville 34.0 MGD 110,000 Knoxville Utilities Board (KUB)
9 Murfreesboro WRRF Murfreesboro 24.0 MGD 150,000 Murfreesboro Water Resources
10 South Jackson WWTP Jackson 20.0 MGD 70,000 Energy Authority (JEA)
11 Johnson City Regional Johnson City 26.0 MGD 90,000 Johnson City Water & Sewer
12 Kingsport WWTP Kingsport 29.0 MGD 55,000 City of Kingsport
13 Clarksville WWTP Clarksville 25.0 MGD 160,000 Clarksville Gas & Water
14 Loves Creek WWTP Knoxville 26.0 MGD 85,000 Knoxville Utilities Board (KUB)
15 Smyrna WWTP Smyrna 15.85 MGD 55,000 Town of Smyrna
16 Cleveland WWTP Cleveland 16.0 MGD 45,000 Cleveland Utilities
17 Columbia WWTP Columbia 14.0 MGD 40,000 Columbia Power & Water
18 Gallatin WWTP Gallatin 12.0 MGD 45,000 Gallatin Public Utilities
19 Franklin WRF Franklin 12.0 MGD 80,000 City of Franklin
20 Oak Ridge West End Oak Ridge 12.0 MGD 30,000 City of Oak Ridge

*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

1. M.C. Stiles Wastewater Treatment Plant

  • Location: Memphis, Shelby County, TN

  • Design Capacity: 135 MGD

  • Current Average Flow: ~95 MGD

  • Operating Authority: City of Memphis Public Works

  • Receiving Water: Mississippi River

Treatment Process: The Stiles plant utilizes a pure oxygen activated sludge process. Due to its discharge into the high-volume Mississippi River, the plant has historically operated without tertiary filtration, focusing on BOD and TSS removal. Recent upgrades are introducing UV disinfection to meet new compliance standards.

Infrastructure & Upgrades: As part of the SARP10 program, the facility is undergoing a massive electrical substation replacement and the installation of a new peracetic acid (PAA) disinfection system to replace chlorine gas.

2. Moccasin Bend Wastewater Treatment Plant

  • Location: Chattanooga, Hamilton County, TN

  • Design Capacity: 140 MGD (Wet Weather Peak >200 MGD)

  • Operating Authority: City of Chattanooga

  • Service Area: Chattanooga and 6 surrounding utility districts

Treatment Process: Moccasin Bend employs High Purity Oxygen activated sludge. It is a regional hub for biosolids processing.

Recent Upgrades: The “Clear Chattanooga” consent decree program has driven significant investment. The standout feature is the installation of the CAMBI Thermal Hydrolysis Process (THP), allowing the plant to produce Class A biosolids and generate significant renewable energy via biogas.

3. Central Wastewater Treatment Plant

  • Location: Nashville, Davidson County, TN

  • Design Capacity: 100 MGD (Peak 440 MGD)

  • Operating Authority: Metro Water Services (MWS)

  • Receiving Water: Cumberland River

Treatment Process: Advanced secondary treatment with biological nutrient removal capabilities. The plant handles the majority of downtown Nashville’s flow.

Infrastructure: MWS is currently executing the “Clean Water Nashville” program. The Central plant recently completed a massive Headworks and Optimization project to handle wet weather flows and reduce Combined Sewer Overflows (CSOs).

4. T.E. Maxson Wastewater Treatment Plant

  • Location: Memphis, Shelby County, TN

  • Design Capacity: 80 MGD

  • Operating Authority: City of Memphis

Treatment Process: Similar to Stiles, Maxson treats a heavy industrial load. It utilizes activated sludge processes and is currently being retrofitted for improved disinfection.

Recent Upgrades: A $100M+ upgrade package is underway to improve process reliability, upgrade sludge lagoons, and install UV disinfection systems.

5. Kuwahee Wastewater Treatment Plant

  • Location: Knoxville, Knox County, TN

  • Design Capacity: 44 MGD (Peak 120 MGD)

  • Operating Authority: Knoxville Utilities Board (KUB)

  • Receiving Water: Tennessee River

Treatment Process: Conventional activated sludge with biological treatment. KUB has aggressively targeted wet-weather storage to manage peak flows.

Compliance: Part of the “Century II” infrastructure management program, KUB has achieved high compliance rates through proactive asset replacement.

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)

Central WWTP Optimization & Headworks (Nashville)

  • Location: Nashville, TN

  • Total Budget: ~$400 Million

  • Funding: Revenue Bonds, WIFIA Loan, SRF

  • Project Scope: Construction of a new headworks facility, grit removal systems, and chemically enhanced primary treatment (CEPT) to handle peak wet weather flows up to 440 MGD.

  • Key Contractors: Brasfield & Gorrie (Construction), Hazen and Sawyer (Design).

  • Status: Late stages of construction; phased commissioning underway.

  • Drivers: Consent Decree compliance to eliminate CSOs into the Cumberland River.

M.C. Stiles & T.E. Maxson Upgrades (Memphis)

  • Location: Memphis, TN

  • Total Budget: $250+ Million (Combined)

  • Funding: SRF Loans, Local Capital Funds

  • Project Scope: Comprehensive rehabilitation including new UV disinfection at Stiles, PAA disinfection at Maxson, and major electrical/blower upgrades.

  • Drivers: Regulatory compliance and aging infrastructure replacement.

  • Timeline: Construction ongoing through 2026.

Murfreesboro WRRF Expansion

  • Location: Murfreesboro, TN

  • Total Budget: $65 Million

  • Project Scope: Expansion of treatment capacity to handle rapid suburban growth; includes advanced nutrient removal technologies.

  • Drivers: Population growth (Murfreesboro is one of the fastest-growing cities in the US).

  • Status: Active Construction.

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

  • Total Active Capital Investment: ~$2.1 Billion (Statewide)

  • Primary Funding Source: TDEC ARP Grants & SRF Loans

  • Largest Single Project: Nashville Central Optimization (~$400M)

  • Top Project Driver: Wet Weather Flow Management / Consent Decrees

  • Key Technology Trend: Shift from Chlorine Gas to UV/PAA Disinfection

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.