Memphis T E Maxson Wastewater Treatment Plant

1. INTRODUCTION

The T.E. Maxson Wastewater Treatment Facility (WWTF) is one of two primary wastewater treatment assets serving the City of Memphis and surrounding Shelby County. Located in southwest Memphis near the Mississippi River, this 90-MGD facility plays a critical role in the regional water infrastructure, handling wastewater from the city’s southern basin, which includes dense residential areas, the Memphis International Airport hub, and the heavy industrial corridor of President’s Island.

Originally commissioned in 1975, the plant is currently concluding a massive, multi-phase modernization effort driven by a Consent Decree and the need to address aging infrastructure. The facility is transitioning from a conventional treatment approach to a more advanced, energy-efficient configuration capable of meeting stringent environmental standards. As part of the City’s Sewer Assessment and Rehabilitation Program (SARP), the T.E. Maxson plant represents a significant capital investment—exceeding $200 million in recent upgrades—aimed at reducing sanitary sewer overflows (SSOs), improving effluent quality discharged to the Mississippi River, and mitigating odors in surrounding communities.

2. FACILITY OVERVIEW

A. Service Area & Coverage

The T.E. Maxson WWTF serves the “South Plant” basin. This service area is distinct from the northern basin served by the M.C. Stiles WWTF. The Maxson catchment area encompasses approximately half of Memphis, including the municipalities of Germantown and Collierville, which discharge into the Memphis interceptor system. The demographic profile is mixed, featuring established residential neighborhoods and significant industrial zones. The influent characteristics are notable for high industrial loading, contributing to varying BOD and COD profiles compared to purely residential facilities.

B. Operational Capacity

The facility is rated for an Average Daily Flow (ADF) of 90 MGD, with a peak hydraulic capacity reaching approximately 200 MGD during wet weather events. Historical flow trends indicate an operating average between 65 and 75 MGD. Due to the age of the collection system in older parts of Memphis, the facility experiences significant peaking factors due to Inflow and Infiltration (I/I) during storm events, necessitating robust hydraulic throughput capabilities.

C. Discharge & Compliance

Treated effluent flows via an outfall structure directly into the Mississippi River. Operations are governed by NPDES Permit TN0020711, issued by the Tennessee Department of Environment and Conservation (TDEC). The permit sets strict limits on Carbonaceous Biochemical Oxygen Demand (CBOD), Total Suspended Solids (TSS), E. coli, and pH. Recent regulatory focus has also shifted toward nutrient monitoring (Nitrogen and Phosphorus) to support Gulf of Mexico hypoxia reduction goals, influencing recent process selection.

3. TREATMENT PROCESS

The T.E. Maxson facility has recently undergone a transition from a simplified contact-stabilization process to a more robust biological nutrient removal configuration. The current treatment train is designed to handle high industrial loads while ensuring consistent compliance.

A. PRELIMINARY TREATMENT

Raw wastewater enters the facility through large interceptors leading to the headworks. The preliminary stage includes:

• Coarse Screening: Automated mechanical bar screens remove large debris, rags, and plastics to protect downstream pumps.
• Grit Removal: Vortex grit chambers utilize centrifugal force to separate heavy inorganic solids (sand, gravel) from the organic waste stream.
• Odor Control: The headworks facility was recently enclosed and fitted with foul air extraction systems scrubbed via biotrickling filters to mitigate local odor nuisances.

Read moreA Comparison Between Aerobic And Anaerobic Wastewater Treatment Technology

B. PRIMARY TREATMENT

Historically, the Maxson plant relied on a configuration that minimized primary treatment in favor of extended aeration. However, modern configurations utilize rectangular primary clarifiers to settle out heavy organic solids. The primary sludge is pumped to the solids handling complex, while the supernatant flows to the secondary treatment biological reactors. This step is critical for reducing the BOD load on the aeration basins.

C. SECONDARY TREATMENT

The core of the Maxson plant’s recent upgrade is the modernization of its secondary treatment system. The process has evolved to a variation of the Activated Sludge process.

• Biological Reactors: The plant utilizes large aeration basins equipped with fine-bubble diffused aeration systems. This replaced older, less efficient mechanical surface aerators. The fine-bubble system provides higher oxygen transfer efficiency (OTE), reducing energy costs.
• Process Configuration: The basins operate to facilitate nitrification (conversion of ammonia to nitrate) and carbon oxidation. The upgraded process control system allows for dissolved oxygen (DO) tapering to optimize biological activity.
• Secondary Clarification: Mixed liquor flows to a battery of circular secondary clarifiers. Here, activated sludge settles and is thickened. A portion is returned to the aeration basins as Return Activated Sludge (RAS) to maintain biomass, while the excess is removed as Waste Activated Sludge (WAS).

D. DISINFECTION

In a major shift from historical chlorination practices or lack of disinfection (common in older Mississippi River permits), the facility now employs a large-scale Ultraviolet (UV) Disinfection system.
The system utilizes TrojanUV 4000Plus (or equivalent high-intensity systems) installed in concrete channels. Effluent passes through banks of UV lamps, which scramble the DNA of pathogens (E. coli, fecal coliform) preventing replication. This method eliminates the need for hazardous chlorine gas storage and dechlorination chemicals (sulfur dioxide/bisulfite), ensuring the effluent is safe for the river ecosystem.

E. SOLIDS HANDLING

Solids management has been a primary focus of recent capital projects:

• Thickening: Primary and waste activated sludge are thickened, often utilizing gravity belt thickeners or rotary drum thickeners.
• Dewatering: The facility utilizes high-solids centrifuges to dewater sludge, producing a “cake” with significantly lower moisture content than previous belt press technologies.
• Disposal: Historically, the plant utilized sludge lagoons, which were significant odor sources. The new solids management plan involves mechanical dewatering followed by hauling to landfills, with long-term plans evaluating thermal drying or beneficial reuse options.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The T.E. Maxson site covers a substantial footprint, largely due to the legacy of large lagoon systems. The site includes the main process buildings, a dedicated administration and laboratory building, and extensive maintenance workshops. The site is leveed to protect against Mississippi River flood stages.

B. Energy Systems

Wastewater treatment is energy-intensive. The recent installation of turbo blowers for the aeration basins represented a significant energy conservation measure, replacing older centrifugal or positive displacement units. The plant’s SCADA system monitors power draw across major motor control centers (MCCs) to optimize peak demand usage.

C. Odor Control

Odor control was a primary driver for recent infrastructure investments. The “Cover and Treat” strategy involved covering the headworks and primary treatment areas. Foul air is conveyed to multi-stage biotrickling filters and activated carbon polishing units. These systems are designed to remove Hydrogen Sulfide (H₂S) and mercaptans, drastically improving air quality for the neighboring West Junction and Boxtown communities.

5. RECENT UPGRADES & MAJOR PROJECTS

The City of Memphis is under a Consent Decree with the EPA and TDEC to address sanitary sewer overflows and plant performance. This has driven the SARP (Sewer Assessment and Rehabilitation Program). The T.E. Maxson facility has seen over $200 million in investment over the last decade.

Upcoming Projects (2025-2027)

Future planning includes the “Maxson Basin Collection System improvements” to reduce I/I before it reaches the plant, and potential evaluation of Peracetic Acid (PAA) as a disinfection backup or alternative. Further automation of the SCADA system is planned to allow for “Digital Twin” process simulation.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

A. Permit Requirements

Operating under NPDES Permit TN0020711, the facility faces the following key effluent parameters (typical values subject to permit cycles):

• CBOD5: Monthly average limit ~25 mg/L (Summer)
• TSS: Monthly average limit ~30 mg/L
• E. Coli: Geometric mean limits (seasonal, typically 126 CFU/100mL)
• Dissolved Oxygen: Minimum 5.0 mg/L

B. Compliance History

Like many older large municipalities, Memphis has faced challenges regarding Sanitary Sewer Overflows (SSOs) within the collection system, leading to the 2012 Consent Decree. The T.E. Maxson plant itself generally maintains compliance with effluent limits, though high river stages and massive wet weather flows present operational challenges. The recent upgrades were specifically designed to ensure consistent compliance with E. coli limits via the new UV system.

7. OPERATIONAL EXCELLENCE

Staffing: The facility is staffed 24 hours a day, 365 days a year. The workforce includes state-certified wastewater operators (Grades III and IV), industrial mechanics, master electricians, and laboratory technicians. The City of Memphis Public Works division emphasizes cross-training and safety certification.

Technology: The migration to a modern SCADA (Supervisory Control and Data Acquisition) system allows operators to monitor dissolved oxygen levels, blower airflow, and UV transmittance in real-time. This automation facilitates “feed-forward” control strategies, adjusting aeration rates based on influent ammonia sensors.

8. CHALLENGES & FUTURE PLANNING

A. Current Challenges

• Inflow & Infiltration (I/I): The Maxson basin includes older infrastructure where stormwater enters sanitary pipes. This dilutes the influent and hydraulically stresses the plant during heavy rains.
• Industrial Loading: Significant industrial dischargers in the President’s Island area can introduce shock loads or slug loads that threaten biological stability.
• Flood Resilience: Located near the Mississippi River, the plant must maintain operations even when the river stage is high, which impacts hydraulic head conditions for the outfall.

B. Future Planning

The “Memphis 2.0” infrastructure plan envisions a fully resilient utility. Long-term goals for Maxson include potential resource recovery (biogas utilization) and further nutrient removal capabilities should regulations on the Mississippi River tighten regarding nitrogen and phosphorus.

9. COMMUNITY & REGIONAL IMPACT

The T.E. Maxson plant is a cornerstone of the regional economy, supporting major industries that require reliable wastewater service. Furthermore, the recent focus on odor control demonstrates the City’s commitment to Environmental Justice, improving the quality of life for residents in Southwest Memphis who have historically lived near the facility’s open lagoons. The improved effluent quality also supports the ecological health of the Mississippi River, a vital commercial and recreational waterway.

10. TECHNICAL SPECIFICATIONS SUMMARY

11. RELATED FACILITIES

The T.E. Maxson plant operates in conjunction with the M.C. Stiles Wastewater Treatment Facility, located in northern Memphis. While they serve different basins, they share management under the City of Memphis Public Works Division. Numerous lift stations throughout the southern basin convey flow to Maxson, including major interceptors from the Germantown area.

12. FAQ SECTION

Technical Questions

1. What is the design capacity of the T.E. Maxson WWTP?
The plant has a design average daily flow of 90 MGD and a peak hydraulic capacity of approximately 200 MGD.

2. Does T.E. Maxson use chlorine for disinfection?
No. As part of recent upgrades, the facility transitioned to Ultraviolet (UV) disinfection to eliminate the safety risks associated with chlorine gas and to meet permit limits without chemical byproducts.

3. What type of aeration system is used?
The plant utilizes fine-bubble diffused aeration powered by high-efficiency turbo blowers, replacing older mechanical surface aerators.

4. Is the plant under a Consent Decree?
Yes, the City of Memphis entered a Consent Decree in 2012 regarding SSOs and effluent compliance. The upgrades at Maxson are a direct result of compliance mandates under this decree.

Public Interest Questions

5. How does the plant control odors?
The facility recently installed covers over the headworks and primary treatment areas and treats the captured air using biotrickling filters and carbon scrubbers.

6. Where does the treated water go?
The treated effluent is discharged via an outfall into the Mississippi River.

7. Who operates the facility?
The facility is owned and operated by the City of Memphis Public Works Division.