Oklahoma City Water Utilities Trust North Canadian Wastewater Treatment Plant

FACILITY BASIC INFORMATION

Plant Name: North Canadian Wastewater Treatment Plant (NCWWTP)

Location: 2313 N Eastern Ave, Oklahoma City, OK 73111

Operating Authority: Oklahoma City Water Utilities Trust (OCWUT)

Design Capacity: 82.0 MGD (Average Daily Flow)

Current Average Flow: ~55-60 MGD

Peak Flow Capacity: ~160 MGD

Service Area: Central Oklahoma City, Nichols Hills, The Village, and parts of Del City/Midwest City

Receiving Water Body: North Canadian River (Oklahoma River)

NPDES/OPDES Permit Number: OK0026212

Read more4D-Printed Smart Materials For Water Treatment

Year Commissioned: 1928 (Major modernizations in 1980s, 2000s, 2010s)

1. INTRODUCTION

The North Canadian Wastewater Treatment Plant (NCWWTP) serves as the flagship facility for the Oklahoma City Water Utilities Trust (OCWUT), acting as the largest of the four wastewater treatment plants serving the metropolitan area. With a design capacity of 82 million gallons per day (MGD), this facility manages the wastewater needs of the city’s dense urban core, treating effluent from major residential districts, the state capitol complex, and significant industrial contributors.

Strategically located near the Adventure District, the plant plays a pivotal role in the environmental health of the North Canadian River, locally known as the Oklahoma River. This receiving water body has been transformed into a premier rowing and recreational venue, necessitating high-performance effluent standards, particularly regarding disinfection and solids removal. Following over $100 million in cumulative upgrades over the last two decades, including a conversion to ultraviolet disinfection and advanced SCADA integration, the NCWWTP exemplifies the transition from conventional sanitation to modern water resource recovery.

2. FACILITY OVERVIEW

A. Service Area & Coverage

The NCWWTP services the “North Canadian” drainage basin, which encompasses the oldest and most densely populated sections of Oklahoma City. The collection system feeding the plant includes over 1,000 miles of gravity mains and force mains. The service area extends to cover municipalities such as The Village and Nichols Hills, as well as receiving flow from the Deep Fork Lift Station. The tributary population is estimated at approximately 350,000 to 400,000 residents, alongside a significant commercial base including the OU Health Center and the Innovation District.

B. Operational Capacity

While the plant is rated for an average design flow of 82 MGD, it typically operates between 55 and 60 MGD during dry weather conditions. The hydraulic profile of the plant is designed to handle peak wet weather flows up to 160 MGD. Historical flow data indicates a stable base load, though infiltration and inflow (I/I) during severe storm events in Oklahoma’s volatile weather climate remain a primary operational variable. The facility is currently operating at approximately 65-70% of its average hydraulic capacity, allowing room for vertical growth within the city center.

C. Discharge & Compliance

Treated effluent is discharged into the North Canadian River. This discharge point is critical as it feeds into the river section used for Olympic-level rowing and kayaking training. Consequently, the Oklahoma Department of Environmental Quality (ODEQ) imposes strict limitations on bacteria levels (Fecal Coliform/E. coli), requiring robust disinfection protocols. The plant operates under the Oklahoma Pollutant Discharge Elimination System (OPDES) permit, consistently meeting standards for Biochemical Oxygen Demand (BOD5) and Total Suspended Solids (TSS).

3. TREATMENT PROCESS

The NCWWTP utilizes a conventional activated sludge process modified for specific site constraints and effluent requirements. The treatment train is designed to ensure robustness against flow variances typical of the region.

Read moreA Comparison Between Aerobic And Anaerobic Wastewater Treatment Technology

A. PRELIMINARY TREATMENT

Raw influent enters the headworks facility where it undergoes screening and grit removal to protect downstream mechanical equipment.

• Screening: Mechanically cleaned bar screens remove large debris, rags, and plastics. Screenings are washed, compacted, and conveyed to dumpsters for landfill disposal.
• Grit Removal: The facility utilizes aerated grit chambers, which introduce air to reduce the specific gravity of the wastewater, allowing heavier inorganic grit (sand, gravel, coffee grounds) to settle while keeping organic material in suspension.
• Flow Measurement: Parshall flumes provide accurate influent flow monitoring for process control and regulatory reporting.

B. PRIMARY TREATMENT

Following preliminary treatment, flow is directed to primary clarifiers. These large circular basins reduce the velocity of the wastewater to allow settleable solids to drop to the bottom as raw sludge, while floatable materials (grease, oil) are skimmed from the surface. The primary treatment stage typically removes 30-35% of BOD and 50-60% of TSS, significantly reducing the organic load on the secondary biological system.

C. SECONDARY TREATMENT

The core of the treatment process is the Activated Sludge System.

• Aeration Basins: The plant operates multiple rectangular aeration basins. Historically, these utilized mechanical surface aerators, but recent upgrades have shifted toward fine bubble diffusion systems to improve oxygen transfer efficiency (OTE) and reduce energy costs. Large centrifugal blowers supply the necessary oxygen to maintain an aerobic environment for the microorganisms.
• Biological Process: A suspended growth culture of microorganisms consumes dissolved organic matter. The Mixed Liquor Suspended Solids (MLSS) concentration is carefully controlled via Return Activated Sludge (RAS) rates.
• Secondary Clarifiers: The mixed liquor flows into circular secondary clarifiers. Here, the biological floc settles out, separating the clear treated water from the biomass. Settled sludge is either returned to the aeration basins (RAS) or wasted (WAS) to the solids handling train.

D. DISINFECTION

In a major departure from historical chlorination practices, the NCWWTP utilizes Ultraviolet (UV) Disinfection. The conversion to UV was driven by safety concerns regarding chlorine gas storage in a populated area and the need to eliminate chlorination byproducts in the receiving stream.

• Technology: High-intensity, low-pressure UV lamp banks (Trojan UV system or equivalent) are submerged in the effluent channel.
• Mechanism: UV light penetrates the cell walls of pathogens, disrupting their DNA/RNA and preventing reproduction.
• Performance: This system effectively manages seasonal compliance limits for bacteria without requiring chemical dechlorination.

F. SOLIDS HANDLING

The solids handling complex at NCWWTP is extensive, managing sludge from both primary and secondary processes.

• Thickening: Waste Activated Sludge (WAS) is thickened, often using Gravity Belt Thickeners (GBT), to reduce hydraulic volume before digestion.
• Anaerobic Digestion: The plant utilizes anaerobic digesters to stabilize the sludge. In the absence of oxygen, mesophilic bacteria break down volatile solids, reducing pathogen counts and producing biogas (methane).
• Dewatering: Digested sludge is dewatered using high-speed Belt Filter Presses. This process increases solids content to approximately 18-22% cake.
• Disposal: The resulting Class B biosolids are trucked off-site for beneficial reuse via land application on permitted agricultural sites, returning nutrients to the soil.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The site spans over 100 acres in Northeast Oklahoma City. The campus includes the main operations building, a fully equipped compliance laboratory, maintenance shops, and the massive concrete tankage structures. The architecture reflects various eras of expansion, from Art Deco influences in original structures to utilitarian industrial design in modern additions.

B. Energy Systems

Wastewater treatment is energy-intensive. The aeration blowers and main effluent pumps are the primary consumers. OCWUT has implemented Variable Frequency Drives (VFDs) on major motors to match energy consumption with biological demand. The facility also captures biogas from the anaerobic digesters, which is used in boilers to heat the digesters, maintaining the mesophilic temperature range required for optimal sludge stabilization.

C. Odor Control

Given its proximity to the Lincoln Park Golf Course and residential zones, odor control is a high priority. The headworks and primary clarifier weirs—typically the most odorous areas—are equipped with covers and air extraction systems. Extracted air is treated through chemical scrubbers or bio-towers to remove hydrogen sulfide ($H_2S$) and other malodorous compounds before release.

5. RECENT UPGRADES & MAJOR PROJECTS

OCWUT actively reinvests in the NCWWTP through its Capital Improvement Plan (CIP). Recent projects focus on reliability, energy efficiency, and asset preservation.

Project ST-0138: Headworks and Aeration Improvements

• Scope: Comprehensive rehabilitation of the preliminary treatment facilities and upgrades to the aeration system.
• Timeline: Completed circa 2018-2020.
• Technical Highlights: Installation of new, high-efficiency screens and washer/compactors to improve the capture of inorganic debris. Replacement of aging blowers with high-efficiency turbo blowers to reduce electrical load.
• Impact: improved protection of downstream pumps and reduced energy consumption by an estimated 15-20%.

Project ST-0150: Solids Handling Improvements

• Scope: Upgrades to the sludge thickening and dewatering equipment.
• Budget: Multi-million dollar investment funded through OCWUT revenue bonds and OWRB loans.
• Technical Highlights: Refurbishment of belt filter presses and sludge transfer pumps. Improvements to the polymer feed systems to optimize dewatering performance.
• Impact: Increased cake solids percentage, reducing the number of hauling trucks required and lowering disposal costs.

SCADA System Migration

A system-wide project to migrate process controls to a unified Rockwell Automation/Allen-Bradley platform. This allows for centralized monitoring, better data historian capabilities, and automated pacing of chemicals and aeration based on real-time sensor data.

6. REGULATORY COMPLIANCE

A. Permit Requirements

The facility operates under OPDES Permit No. OK0026212. Key effluent limitations typically include:

• CBOD5: Monthly average limits generally < 20 mg/L (seasonally variable).
• TSS: Monthly average limits generally < 30 mg/L.
• pH: Maintained between 6.5 and 9.0 s.u.
• DO (Dissolved Oxygen): Minimum requirements to ensure river health (typically > 5.0 mg/L).
• Bacteria: Seasonal limits on Fecal Coliform/E. coli for recreational water contact (May-September).

B. Compliance History

The NCWWTP maintains a strong record of compliance with the Oklahoma DEQ. Occasional excursions are typically related to extreme wet weather events where hydraulic peaking factors challenge the secondary clarifier settlability. OCWUT proactively reports these events and manages them through wet weather operating protocols.

7. CHALLENGES & FUTURE PLANNING

A. Aging Infrastructure

With core components dating back several decades, corrosion and concrete degradation are constant challenges. OCWUT employs an aggressive Asset Management Program to prioritize rehabilitation of concrete basins and replacement of corroded piping.

B. Nutrient Regulations

While current permits focus on carbonaceous removal (BOD) and solids, regional trends suggest future permits will include tighter limits on Total Nitrogen (TN) and Total Phosphorus (TP) to prevent eutrophication in downstream reservoirs. Future master planning for NCWWTP includes footprint allocation for Biological Nutrient Removal (BNR) upgrades.

C. Wet Weather Management

Inflow and Infiltration (I/I) from the aging collection system in central OKC results in high peaking factors. Future planning involves not just plant expansion, but significant investment in the collection system to line pipes and seal manholes, reducing the hydraulic load arriving at the plant.

8. TECHNICAL SPECIFICATIONS SUMMARY

9. FAQ SECTION

Technical Questions

1. Does the NCWWTP perform Biological Nutrient Removal (BNR)?
Currently, the plant operates as a conventional carbonaceous removal facility. However, the process can be tuned for partial nitrification, and future master plans account for BNR implementation should regulatory limits for Nitrogen and Phosphorus tighten.

2. What is the solids retention time (SRT) for the biological process?
SRT varies by season to maintain nitrification efficiency, typically ranging from 5 to 10 days depending on wastewater temperature and mixed liquor volatile suspended solids (MLVSS) targets.

3. How is the plant powered?
The plant relies on grid power from OG&E but has backup generation capabilities for critical loads. Biogas generated in digesters is utilized for process heating, offsetting natural gas consumption.

Public Interest Questions

4. Is the discharged water safe for the river?
Yes. The effluent undergoes rigorous treatment and UV disinfection, meeting strict state standards designed to protect aquatic life and allow for secondary contact recreation (like boating) in the Oklahoma River.

5. Why does the plant sometimes have an odor?
Wastewater treatment inherently involves organic breakdown. While the plant uses scrubbers to treat air from headworks and primary tanks, weather inversions or maintenance on odor control units can sometimes allow odors to escape the fenceline. OCWUT actively monitors this to minimize community impact.

6. Where does the waste go?
The “clean” water goes to the river. The solids (sludge) are treated, stabilized, and used as a fertilizer on agricultural land, recycling nutrients back into the earth rather than filling up landfills.

Disclaimer: This page is an independent technical resource and is not the official website of the Oklahoma City Water Utilities Trust. All data is based on publicly available engineering reports, permits, and planning documents as of 2023.