City Of Norman Wastewater Treatment Plant

1. INTRODUCTION

The Norman Water Reclamation Facility (WRF) serves as the primary wastewater treatment asset for the City of Norman, Oklahoma, and the University of Oklahoma. Following a significant operational overhaul completed in 2017, the facility now boasts a rated design capacity of 17 million gallons per day (MGD). Operated by the Norman Utilities Authority (NUA), the plant is a critical component of the region’s environmental stewardship, discharging treated effluent into the South Canadian River.

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The facility is distinct in the region for its adoption of innovative compact technologies, specifically the integration of Salsnes Filter technology for primary treatment during its recent Phase 2 expansion. This strategic engineering choice allowed the NUA to expand capacity within a constrained geographic footprint while meeting increasingly stringent Oklahoma Department of Environmental Quality (ODEQ) standards. Today, the Norman WRF represents a model of modern biological nutrient removal (BNR) and energy-efficient operations in the Southern Great Plains.

2. FACILITY OVERVIEW

A. Service Area & Coverage

The WRF services the entirety of the City of Norman, the third-largest city in Oklahoma, covering approximately 189 square miles. The service area includes a diverse mix of residential zones, commercial districts, and the significant institutional load generated by the University of Oklahoma. The collection system comprises over 500 miles of sanitary sewer lines and roughly 15 lift stations that convey wastewater to the centralized treatment facility located south of the urban core.

B. Operational Capacity

The plant operates with a design average flow of 17 MGD and a peak hourly flow capacity of approximately 42 MGD. Historically, the plant operated at a 12 MGD capacity prior to the Phase 2 expansion. Current flows average between 11.5 and 13 MGD, providing the municipality with a capacity cushion to accommodate projected population growth through 2030. The hydraulic profile of the plant is designed to handle significant wet-weather events, a common challenge in the region due to inflow and infiltration (I&I).

C. Discharge & Compliance

Treated effluent is discharged into the South Canadian River via a dedicated outfall. The facility operates under the Oklahoma Pollutant Discharge Elimination System (OPDES), administered by the ODEQ. The receiving stream is classified for agriculture, industrial and municipal process and cooling water, and primary body contact recreation. Consequently, the facility must strictly adhere to limits regarding Dissolved Oxygen (DO), E. coli, and nutrient loading to prevent degradation of the river ecosystem.

3. TREATMENT PROCESS

A. PRELIMINARY TREATMENT

Raw influent enters the headworks where it undergoes aggressive screening and grit removal. The facility utilizes mechanical bar screens to remove large debris, rags, and plastics that could damage downstream pumps. Following screening, a vortex grit removal system extracts abrasive inorganic materials (sand, gravel) to protect mechanical equipment. The headworks is enclosed and ventilated through a chemical scrubber system to mitigate odors, a critical requirement given the facility’s proximity to public recreational areas.

B. PRIMARY TREATMENT (Innovative Technology)

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Unlike traditional plants utilizing large gravity clarifiers, the Norman WRF employs Salsnes Filter technology for primary treatment. This rotating belt sieve system filters suspended solids from the wastewater. This choice was driven by land constraints during the Phase 2 expansion. The Salsnes filters provide equivalent TSS removal to primary clarifiers (removing 30-60% of TSS) but occupy approximately 10% of the footprint. The solids removed are dewatered directly within the unit, streamlining the solids handling process.

C. SECONDARY TREATMENT

The biological heart of the Norman WRF consists of Vertical Loop Reactors (VLRs). These are modified oxidation ditches that use surface aerators and a deep-tank configuration to achieve high oxygen transfer efficiency. The VLRs are operated to facilitate Biological Nutrient Removal (BNR), specifically targeting ammonia reduction through nitrification and denitrification zones.

Following aeration, the mixed liquor flows to secondary clarifiers. These large circular tanks allow the biological floc to settle. The clear supernatant overflows the weirs, while the settled biomass is either returned to the VLRs as Return Activated Sludge (RAS) to maintain the biological population or removed as Waste Activated Sludge (WAS) for processing.

D. TERTIARY TREATMENT

To meet stringent effluent requirements, particularly for suspended solids and turbidity, the secondary effluent passes through cloth media disk filters. These filters provide a physical barrier to remaining particulate matter, ensuring a high-quality effluent suitable for effective UV disinfection.

E. DISINFECTION

The facility utilizes Ultraviolet (UV) Irradiation for disinfection, having moved away from chlorine gas to enhance safety and eliminate the formation of disinfection byproducts. The UV system (TrojanUV) exposes the effluent to high-intensity UV light, inactivating pathogens (bacteria and viruses) by disrupting their DNA/RNA, rendering them unable to replicate. The flow is then re-aerated (cascade aeration) to raise dissolved oxygen levels before discharge into the South Canadian River.

F. SOLIDS HANDLING

Primary sludge (from Salsnes filters) and WAS are combined and stabilized. The facility utilizes aerobic digestion to reduce volatile solids and pathogen content. Following digestion, the biosolids are dewatered using high-performance Belt Filter Presses. The dewatered cake is then transported to the adjacent Norman Compost Facility, where it is co-composted with yard waste to produce a Class A biosolid soil amendment, demonstrating a sustainable closed-loop waste management strategy.

G. PROCESS CONTROL

The entire facility is monitored via a centralized SCADA (Supervisory Control and Data Acquisition) system. Operators monitor Dissolved Oxygen (DO) profiles in the VLRs, Oxidation Reduction Potential (ORP), and return rates in real-time to optimize energy consumption and treatment efficacy.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The Norman WRF is situated on a compact site south of Jenkins Avenue. The layout is optimized for hydraulic efficiency. The site includes the Administration Building, which houses the laboratory and control center, the Maintenance Building, and the dedicated compost facility located immediately adjacent to the treatment train.

B. Energy Systems

Energy efficiency was a primary driver in the recent plant design. The use of VLRs allows for turndown capability on aeration rotors based on oxygen demand, significantly reducing electrical load during low-flow or low-loading periods. The Salsnes filters operate with minimal horsepower compared to the scraper mechanisms and pumps associated with conventional primary clarifiers.

C. Odor Control

Given the plant’s location near the Canadian River recreational areas and potential future development, odor control is paramount. The headworks and solids handling buildings are under negative pressure, with foul air treated through packed-tower wet scrubbers and activated carbon polishing units to ensure neutral air discharge.

5. RECENT UPGRADES & MAJOR PROJECTS

WRF Phase 2 Expansion – $62 Million (2013-2017)

• Project Scope: Comprehensive plant expansion and technology retrofit.
• Project Budget: ~$62 Million
• Funding Sources:
  • Oklahoma Water Resources Board (OWRB) Loans
  • Clean Water State Revolving Fund (CWSRF)
  • Local Utility Rates

• Key Contractors:
  • Design Engineer: Garver
  • General Contractor: Archer Western

• Technical Highlights:
  • Installation of **Salsnes Filter** technology to replace aging primary clarifiers, saving significant site space.
  • Construction of new **Vertical Loop Reactors (VLRs)** for advanced biological treatment.
  • New UV disinfection building.
  • New blower building and standby power generation.

• Results Achieved:
  • Increased capacity from 12 MGD to 17 MGD.
  • Achieved consistent compliance with ammonia and nutrient removal standards.
  • Reduced operational footprint for primary treatment by over 80%.

Current/Upcoming Projects (2024-2027)

Indirect Potable Reuse (IPR) Pilot: The City of Norman is currently investigating Indirect Potable Reuse to augment the water supply at Lake Thunderbird. While the WRF currently discharges to the river, future plans involve advanced treatment (potentially RO/AOP) to treat effluent to drinking water standards for environmental buffer discharge. This is in the planning and pilot study phases as part of the “Norman 2060” strategic water supply plan.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

A. Permit Requirements

The Norman WRF operates under OPDES Permit No. OK0029181. Key discharge parameters include:

• BOD5: Weekly Average limit typically < 20 mg/L (seasonally variable)
• TSS: Weekly Average limit typically < 30 mg/L
• Ammonia (NH3-N): Strict limits (often < 2.0 mg/L) during summer months to prevent toxicity.
• E. Coli: Daily max limits for recreational water protection.
• Dissolved Oxygen: Minimum 5.0 mg/L (summer).

B. Compliance History

Following the Phase 2 expansion, the facility has maintained an excellent compliance record. The upgrade specifically addressed historical challenges regarding ammonia toxicity and wet-weather hydraulic overloads. The facility has received recognition from the Oklahoma Water Environment Association (OWEA) for safety and operational excellence.

C. Environmental Stewardship

The Norman WRF is a regional leader in biosolids reuse. By integrating with the municipal yard waste composting program, the facility diverts thousands of tons of waste from landfills annually, creating a nutrient-rich soil conditioner available to the public.

7. OPERATIONAL EXCELLENCE

The facility is staffed by approximately 25 personnel, including licensed operators, maintenance technicians, laboratory analysts, and administrative staff. The NUA requires high-level certification (Class A or B) for lead operators. The on-site laboratory is state-certified for standard process control parameters (pH, DO, TSS, Ammonia), ensuring real-time data is available for process adjustments.

The plant utilizes an Asset Management Program to track equipment lifecycle, schedule preventative maintenance, and optimize capital replacement budgets, moving from reactive to predictive maintenance strategies.

8. CHALLENGES & FUTURE PLANNING

A. Current Challenges

Like many municipalities, Norman faces challenges with **Inflow and Infiltration (I&I)**. During severe Oklahoma thunderstorms, stormwater enters the sanitary sewer system, causing hydraulic spikes at the plant. The Phase 2 expansion improved the plant’s ability to handle these peaks, but collection system rehabilitation remains a priority.

B. Future Planning: Water Reuse

The most significant future challenge is water scarcity. The City of Norman relies on Lake Thunderbird and the Garber-Wellington Aquifer. The WRF is pivotal to the city’s long-term water security strategy (Norman 2060). Future phases will likely involve upgrading a portion of the plant flow to advanced purification standards for augmentation of Lake Thunderbird, closing the water loop.

9. COMMUNITY & REGIONAL IMPACT

The Norman WRF supports the economic growth of the University of Oklahoma and the surrounding technological corridors. By ensuring reliable wastewater capacity, the facility enables residential and commercial development. Furthermore, the co-composting operation is a popular community service, providing residents with high-quality compost while educating the public on resource recovery.

10. TECHNICAL SPECIFICATIONS SUMMARY

11. RELATED FACILITIES

Norman Compost Facility: Located adjacent to the WRF, this facility receives dewatered biosolids cake and mixes it with chipped brush and yard waste. It is a critical component of the solids handling train.

Vernon Campbell Water Treatment Plant: The city’s drinking water facility, which may eventually receive augmented raw water supply from future WRF reuse projects.

12. FAQ SECTION

Technical Questions

• What is the design capacity of the Norman WRF?
  The facility is rated for an average daily flow of 17 MGD following the Phase 2 expansion.
• Does the Norman WRF perform nutrient removal?
  Yes. The Vertical Loop Reactors (VLRs) are designed for biological nutrient removal, specifically targeting ammonia and nitrogen reduction.
• What technology is used for primary treatment?
  The facility utilizes Salsnes Filter technology (rotating belt sieves) instead of conventional primary clarifiers to save space and enhance carbon capture.
• Is there a water reuse program?
  Currently, the plant practices beneficial reuse of biosolids via composting. The city is actively piloting Indirect Potable Reuse (IPR) for future water supply augmentation.

Public Interest Questions

• Does the plant smell?
  The facility utilizes advanced chemical scrubbers and carbon filters at the headworks and solids handling areas to minimize odors, though occasional odors may occur during maintenance or upset conditions.
• Where does the treated water go?
  The highly treated effluent is discharged into the South Canadian River, where it supports the local ecosystem.
• Can I get compost from the facility?
  Yes, the Norman Compost Facility offers compost derived from the treatment process for sale to the public.