Lexington Fayette Urban County Government Town Branch Wastewater Treatment Plant

1. INTRODUCTION

The Town Branch Wastewater Treatment Plant is the oldest and largest of two major wastewater treatment facilities serving the Lexington-Fayette Urban County Government (LFUCG) area. Situated just west of downtown Lexington, the plant is a critical component of the region’s hydrology, discharging into Town Branch Creek—a waterway that consists almost entirely of effluent during dry weather conditions.

Currently operating under a stringent EPA Consent Decree initiated in 2006 (and modified thereafter), the facility has been the focal point of hundreds of millions of dollars in infrastructure investment. These remedial measures aim to eliminate sanitary sewer overflows (SSOs) and manage wet weather surges. With a peak hydraulic capacity of 64 MGD and advanced anaerobic digestion capabilities, the Town Branch facility represents a complex integration of legacy infrastructure and modern wet-weather management technologies.

2. FACILITY OVERVIEW

A. Service Area & Coverage

The facility serves the “Town Branch” sewershed, which encompasses the dense urban core of Lexington, the University of Kentucky campus, and the expanding northern suburbs. The service area is characterized by a mix of older combined sewer systems (in the downtown core) and separated sanitary sewers in outlying areas. The topography of the Inner Bluegrass region directs gravity flow toward the plant, necessitating a complex network of trunk lines and lift stations.

B. Operational Capacity

Design Capacity: The plant is rated for an average daily flow of 30 MGD. However, the critical engineering parameter for this facility is its response to wet weather. The plant is designed to handle a peak hydraulic flow of 64 MGD through full secondary treatment. Flows exceeding this capacity are diverted to auxiliary wet weather storage and treatment systems to prevent system bypasses.

C. Discharge & Compliance

The plant discharges into Town Branch Creek at Mile Point 5.9. Because the receiving stream has very low natural flow (7Q10 of essentially zero), the plant’s effluent often constitutes the majority of the stream’s volume. This designates the receiving water as “effluent dominated,” resulting in highly stringent NPDES permit limits regarding dissolved oxygen (DO), ammonia-nitrogen, and whole effluent toxicity (WET) to protect aquatic life in the downstream Elkhorn Creek basin.

3. TREATMENT PROCESS

A. Preliminary Treatment

Raw wastewater enters the headworks via multiple trunk lines. The preliminary treatment stage was significantly upgraded to handle variable flows and protect downstream mechanical equipment.

• Screening: Multi-rake mechanical bar screens remove coarse debris, rags, and plastics.
• Grit Removal: Vortex grit chambers utilize centrifugal force to settle out inorganic solids (sand, gravel, coffee grounds) while keeping organic material in suspension.
• Odor Control: Due to its proximity to the budding Town Branch Park and the Distillery District, the headworks are enclosed and ventilated through biological scrubbers and activated carbon units.

B. Primary Treatment

Flow moves to rectangular primary clarifiers. These tanks reduce the velocity of the wastewater, allowing settleable solids to drop to the bottom as primary sludge and floatables (grease/oil) to be skimmed from the surface. The primary treatment stage is essential for reducing the BOD load on the subsequent biological stage by approximately 30-35%.

C. Secondary Treatment

The biological treatment train utilizes a conventional activated sludge process modified for nitrification.

• Aeration Basins: The plant utilizes plug-flow aeration basins equipped with fine-bubble diffused aeration systems. Blowers provide the necessary oxygen for microorganisms to metabolize organic matter and convert ammonia to nitrate (nitrification).
• Secondary Clarifiers: Mixed liquor flows to circular secondary clarifiers where the biological floc settles. A portion of the settled solids is returned to the head of the aeration basins (Return Activated Sludge – RAS), while the excess biomass is wasted (Waste Activated Sludge – WAS) to the solids handling train.

D. Disinfection

Historically a chlorination/dechlorination facility, Town Branch has transitioned toward Ultraviolet (UV) disinfection in recent upgrades to improve safety and reduce chemical byproducts in the receiving stream. The UV system must ensure compliance with fecal coliform and E. coli limits before the water flows over the cascade aeration steps and into the outfall.

E. Solids Handling

Town Branch serves as the regional solids processing center, often receiving sludge from the West Hickman plant.

• Thickening: Gravity belt thickeners reduce the water content of WAS.
• Anaerobic Digestion: Primary sludge and thickened WAS are stabilized in anaerobic digesters. The process operates at mesophilic temperatures, reducing pathogen counts and volatile solids while producing biogas.
• Dewatering: Digested sludge is dewatered using high-performance belt filter presses.
• Disposal: The resulting Class B biosolids are hauled off-site for beneficial reuse via land application on permitted farmland in surrounding counties.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The site is constrained by urban development, bordered by the Town Branch creek, historic distilleries, and waste management facilities. The architecture is strictly industrial, though recent efforts have been made to improve aesthetics and fencing to integrate with the revitalization of the Manchester Street corridor.

B. Wet Weather Storage

A defining feature of the Town Branch infrastructure is the extensive wet weather management system. This includes large equalization basins (EQ) designed to shave peak flows during storm events. Stored wastewater is returned to the headworks for full treatment once hydraulic capacity becomes available, preventing unpermitted discharges.

C. Odor Control Systems

Odor control is a primary operational KPI due to the “Town Branch Commons” greenway project. The facility employs a multi-stage approach including chemical misting systems at perimeter fences and negative pressure containment in solids handling buildings, treated through bio-towers.

5. RECENT UPGRADES & MAJOR PROJECTS

LFUCG has been executing a comprehensive Remedial Measures Plan (RMP) driven by a Consent Decree with the EPA and the Commonwealth of Kentucky.

Town Branch Wet Weather Flow Transfer (2018-2022)

• Project Scope: Construction of new large-diameter force mains and pump station upgrades to manage wet weather surges.
• Budget: Part of the wider ~$590 million consent decree spending.
• Objective: To convey peak flows efficiently to the plant and storage facilities, eliminating SSOs in the collection system.

Plant Improvements & Nutrient Removal

• Scope: Upgrades to aeration systems and chemical feed facilities (Ferric Chloride) to enhance phosphorus removal and ensure consistent nitrification during cold weather.
• Driver: While the Consent Decree focused on quantity (capacity), parallel regulatory pressure focused on quality (nutrients) regarding the Gulf of Mexico Hypoxia operational strategy.

Upcoming: Biogas Utilization & Efficiency

LFUCG is currently evaluating options to optimize energy recovery from the anaerobic digesters. While biogas is currently used for process heating (digester heating), future plans consider Combined Heat and Power (CHP) to offset grid electrical consumption.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

Permit Requirements (NPDES KY0020982)

The permit reflects the low dilution capacity of Town Branch Creek.

• CBOD5: Monthly average limits typically ≤ 10 mg/L (Summer).
• TSS: Monthly average limits typically ≤ 30 mg/L.
• Ammonia-Nitrogen (NH3-N): Highly restrictive summer limits (often < 2.0 mg/L) to prevent toxicity.
• Phosphorus: Monitoring and reporting required; optimization is ongoing to meet statewide nutrient reduction goals.

Compliance History

Since the implementation of the Consent Decree projects, the frequency of bypasses and overflows has dropped significantly. The plant consistently achieves high removal efficiencies for BOD and TSS (typically >95%). The primary compliance challenge remains managing peak inflow and infiltration (I/I) during severe weather events typical of the Ohio Valley climate.

7. OPERATIONAL EXCELLENCE

Staffing & Certification

The plant is staffed 24/7. Operators must hold Kentucky Class IV Wastewater Treatment certification—the highest level in the state—due to the complexity of the activated sludge and solids handling processes. The Division of Water Quality emphasizes cross-training between the Town Branch and West Hickman facilities.

SCADA & Automation

A robust SCADA system monitors thousands of I/O points, allowing operators to adjust Return Activated Sludge (RAS) rates, dissolved oxygen setpoints, and chemical dosing in real-time. This automation is critical for managing the “first flush” of storm events without washing out the biological mass.

8. CHALLENGES & FUTURE PLANNING

A. Inflow and Infiltration (I/I)

The historic nature of downtown Lexington’s sewer infrastructure means the plant sees rapid hydraulic spikes during rainfall. While storage tanks help, the ultimate solution involves continuous rehabilitation of the collection system (lining pipes, separating sewers) to reduce the hydraulic load arriving at the plant.

B. Urban Encroachment

The Town Branch corridor is currently the site of Lexington’s most aggressive urban revitalization project. The plant, once on the “back side” of town, is now adjacent to high-value recreational and commercial real estate. This increases pressure for flawless odor control, noise reduction, and aesthetic screening.

C. Emerging Contaminants

Like all major utilities, LFUCG is monitoring regulatory horizons regarding PFAS (Per- and polyfluoroalkyl substances). As a receiver of landfill leachate or industrial flows, future treatment trains may require advanced filtration (GAC or Reverse Osmosis) if EPA establishes strict effluent limits for PFAS.

9. TECHNICAL SPECIFICATIONS SUMMARY

10. FAQ SECTION

Technical Questions

Q: How does Town Branch WWTP handle flows exceeding 64 MGD?
A: Flows exceeding secondary treatment capacity are diverted to on-site flow equalization (storage) basins. These basins hold the diluted wastewater until the storm subsides, at which point the water is pumped back to the headworks for full treatment.

Q: Does the facility perform nutrient removal?
A: Yes. The activated sludge process is operated to achieve nitrification (ammonia removal). While not originally designed for biological phosphorus removal, chemical precipitation (using Ferric Chloride) is employed to reduce phosphorus levels.

Q: What is the status of the EPA Consent Decree?
A: LFUCG is in the advanced stages of the Remedial Measures Plan. Significant completion has been achieved on storage tanks and plant upgrades, with ongoing work focused on collection system rehabilitation.

Public Interest Questions

Q: Why is there sometimes an odor near Manchester Street?
A: Wastewater treatment naturally generates odors (hydrogen sulfide). While the plant uses advanced scrubbers and carbon filters to capture 99% of these odors, atmospheric inversions or maintenance activities can sometimes allow odors to escape. LFUCG actively monitors and mitigates these issues.

Q: Is the water discharged into Town Branch clean?
A: Yes. The effluent meets strict state and federal standards for clarity, bacteria, and oxygen content. In dry months, the clear water seen in Town Branch Creek is almost entirely treated water from the plant.