City Of Broken Arrow Wastewater Treatment Plant

TARGET AUDIENCE

• Municipal consulting engineers evaluating SBR (Sequencing Batch Reactor) applications.
• Wastewater treatment plant operators and utility managers.
• Environmental regulators (ODEQ/EPA) tracking watershed compliance.
• Engineering firms pursuing hydraulic improvement and flow equalization projects.

Read more10 Surprising Benefits of Upgrading Your Aeration Tank System
• Biosolids managers interested in municipal composting operations.

1. INTRODUCTION

The Lynn Lane Wastewater Treatment Plant (LLWTP) serves as the primary municipal treatment facility solely owned and operated by the City of Broken Arrow, Oklahoma. As the city has evolved into one of the state’s fastest-growing municipalities, the LLWTP has transitioned from conventional treatment methods to an advanced Sequencing Batch Reactor (SBR) system. The facility is critical to the region’s water quality management, treating an average of roughly 6 million gallons daily (MGD) before discharging into Adams Creek.

Beyond liquid stream treatment, the facility is distinguished by its integration with the city’s award-winning composting program, which diverts biosolids from landfills to create beneficial soil amendments. Following significant investments in hydraulic peak flow management—including the construction of a massive Flow Equalization Basin (FEB)—the plant represents a model of modernization focused on regulatory compliance, wet-weather resilience, and sustainable solids handling.

2. FACILITY OVERVIEW

A. Service Area & Coverage

The City of Broken Arrow operates a split wastewater system. The northern and eastern portions of the city flow to the Lynn Lane Wastewater Treatment Plant, while the southern and western portions are directed to the Haikey Creek Wastewater Treatment Plant (a regional facility operated by the Regional Metropolitan Utility Authority—a partnership between Tulsa and Broken Arrow). The LLWTP specifically serves the rapid residential and commercial expansion in the Wagoner County portion of the city. The collection system feeding Lynn Lane is characterized by a mix of gravity lines and lift stations dealing with significant topographic variations.

B. Operational Capacity

The facility has a design average daily flow of 8.0 MGD. However, like many municipalities in the region, Broken Arrow faces challenges related to Inflow and Infiltration (I/I) during severe weather events. Historically, peak wet weather flows have stressed the biological systems, necessitating the recent focus on hydraulic buffering. The plant is currently operating at approximately 70-75% of its average organic design capacity, allowing room for continued municipal growth.

C. Discharge & Compliance

Treated effluent is discharged into Adams Creek, which flows into the Verdigris River system. The plant operates under the Oklahoma Pollutant Discharge Elimination System (OPDES) permit administered by the Oklahoma Department of Environmental Quality (ODEQ). Stringent limits are placed on Dissolved Oxygen (DO), Total Suspended Solids (TSS), Carbonaceous Biochemical Oxygen Demand (CBOD), and E. coli. The facility has maintained a strong record of compliance, particularly following the implementation of UV disinfection and flow equalization strategies.

3. TREATMENT PROCESS

The Lynn Lane facility utilizes a modified activated sludge process featuring Sequencing Batch Reactors (SBR). This technology allows for equalization, aeration, and clarification to occur within a single basin, providing operational flexibility and a smaller physical footprint compared to conventional flow-through systems.

A. PRELIMINARY TREATMENT

Raw wastewater enters the headworks where it passes through mechanical bar screens to remove large debris, rags, and plastics. This is followed by a vortex grit removal system designed to settle out sand, gravel, and inorganic solids that could damage downstream pumps. The screened and de-gritted wastewater is then measured via Parshall flumes before entering the biological stage. Odor control at the headworks is managed via chemical scrubbers to mitigate nuisance odors for nearby developments.

B. SECONDARY TREATMENT (SBR)

The core of the treatment process consists of multiple Sequencing Batch Reactor basins. The SBR process operates on a timed cycle consisting of four phases:

• Fill: Wastewater enters the basin and mixes with the biomass (mixed liquor).
• React (Aeration): Fine bubble diffusers provide oxygen, allowing microorganisms to consume organic matter and nitrify ammonia.
• Settle (Clarification): Aeration and mixing stop, allowing the biomass to settle to the bottom, creating a clear supernatant at the top. This eliminates the need for separate secondary clarifiers.
• Decant: A mechanical decanter lowers into the tank to draw off the clear, treated water (effluent) without disturbing the settled sludge.

C. DISINFECTION

Following the SBR decant phase, the effluent flows to the Ultraviolet (UV) disinfection facility. The plant transitioned from chlorine gas to UV to improve safety and eliminate the formation of disinfection byproducts. The UV system utilizes banks of low-pressure, high-output lamps to inactivate pathogens (specifically E. coli) by disrupting their DNA. This system is automatically paced based on flow rate and UV transmittance (UVT).

D. SOLIDS HANDLING & COMPOSTING

Waste Activated Sludge (WAS) is wasted from the SBR basins to aerobic digesters for stabilization and volatile solids reduction. The digested sludge is then pumped to the dewatering building, which utilizes belt filter presses to produce a cake with 15-18% solids concentration.

Beneficial Reuse: Unlike facilities that landfill their solids, Broken Arrow transports dewatered biosolids to its on-site composting facility. Here, the biosolids are mixed with green waste (wood chips, yard debris collected from residents) and processed in windrows. The result is a Class A Exceptional Quality (EQ) compost sold to the public, closing the sustainability loop.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The site encompasses significant acreage to accommodate the SBR basins, the massive flow equalization basin, and the adjacent composting operation. The administration building houses the SCADA control room and a NELAP-accredited laboratory capable of performing daily process control tests and permit-required analysis for pH, DO, and solids.

B. Flow Equalization Basin (FEB)

A dominant feature of the site infrastructure is the Flow Equalization Basin. Constructed to manage wet-weather peaking, this concrete-lined reservoir allows the plant to divert excess influent during storms. The stored water is then returned to the headworks for full treatment once flows subside, preventing washouts of the biological biomass in the SBRs.

C. Energy Systems

The plant is a significant energy consumer, primarily driven by the large blowers required for the SBR aeration phase. Energy efficiency upgrades have focused on Variable Frequency Drives (VFDs) for the main blower assemblies and pumps, allowing motor speeds to match biological demand rather than running at full speed continuously.

5. RECENT UPGRADES & MAJOR PROJECTS

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

A. Permit Requirements

The facility operates under OPDES Permit OK0026921. Key discharge parameters include:

• CBOD5: Monthly average limits typically ≤ 10-15 mg/L depending on season.
• TSS: Monthly average ≤ 15-20 mg/L.
• Ammonia (NH3-N): Seasonal limits, often < 2 mg/L in summer to protect aquatic life toxicity.
• E. Coli: < 126 colonies/100ml (Geometric Mean) during recreation season (May-Sept).

B. Environmental Stewardship

The City of Broken Arrow has received recognition for its water reclamation efforts. By maintaining strict compliance with nutrient and bacteria limits, the LLWTP protects the ecosystem of Adams Creek. Furthermore, the co-composting facility creates a circular economy, turning waste products into a revenue-generating soil conditioner used by local residents and landscaping crews.

7. OPERATIONAL EXCELLENCE

A. Staffing & Certification

The plant is staffed by a team of licensed operators, mechanics, and lab technicians. Oklahoma DEQ requires high-level certification (Class A or B) for lead operators due to the complexity of the SBR system and the reuse components. The utility places a strong emphasis on continuing education and safety training.

B. Technology Integration

The LLWTP utilizes a robust SCADA (Supervisory Control and Data Acquisition) system. This allows operators to monitor SBR cycle times, dissolved oxygen levels, and tank levels in real-time. The system also automates the diversion of flow to the FEB during storm events, a critical function that previously required manual intervention.

8. CHALLENGES & FUTURE PLANNING

A. Rapid Urban Growth

Broken Arrow is one of the fastest-growing cities in the region. As farmland converts to subdivisions, the hydraulic loading on the plant increases. The City’s Master Plan anticipates the eventual need to expand the Lynn Lane plant beyond its current 8 MGD capacity or divert additional flow to the regional Haikey Creek facility.

B. Aging Infrastructure

While the SBRs are relatively modern, the original conveyance piping and some headworks structures date back to the 1980s. A comprehensive asset management program is underway to identify critical failure points and prioritize replacement of pumps, valves, and electrical switchgear.

C. Nutrient Regulations

Emerging regulations regarding total phosphorus and total nitrogen in the Arkansas River basin may require future retrofits. While SBRs are naturally good at nutrient removal through cycle manipulation (anoxic/oxic phases), stricter limits may require chemical addition (alum/ferric) or tertiary filtration in the future.

9. TECHNICAL SPECIFICATIONS SUMMARY

10. RELATED FACILITIES

Haikey Creek Wastewater Treatment Plant: A 16 MGD regional facility located in south Broken Arrow. It is operated by the RMUA (a joint venture between Broken Arrow and Tulsa). Approximately half of Broken Arrow’s sewage flow (southern basin) is treated here.

Verdigris River Water Treatment Plant: The city’s potable water production facility, which draws from the river downstream of the wastewater discharge, necessitating high treatment standards at LLWTP.

11. FAQ SECTION

Technical Questions

1. Why does Lynn Lane use SBR technology instead of conventional activated sludge?
SBRs provide a smaller footprint and the ability to control nitrification and denitrification within a single tank by adjusting cycle times, which is efficient for the variable flows the plant experiences.

2. How does the Flow Equalization Basin (FEB) interact with the treatment train?
During high flow events (storms), influent in excess of the biological capacity is diverted to the FEB. Once the storm subsides, this water is pumped back to the headworks at a controlled rate to be fully treated.

3. Does the plant produce Class A or Class B biosolids?
Through the composting process, the facility produces Class A “Exceptional Quality” compost, which is safe for public use in gardens and lawns.

Public Interest Questions

4. Does the plant smell?
The City utilizes chemical scrubbers at the headworks and manages the composting windrows carefully to minimize odors. However, slight earthy odors are natural near wastewater facilities.

5. Can I buy compost from the facility?
Yes, the City of Broken Arrow creates compost from the biosolids and yard waste, which is often available for residents to purchase or pick up.

6. Who do I contact for a tour?
Tours are typically arranged through the City of Broken Arrow Utilities Department for educational groups and engineering students.