City Of Columbus North Highlands Water Resource Facility

FACILITY BASIC INFORMATION

Plant Name: North Columbus Water Resources Facility (NCWRF)

Location: Columbus, Muscogee County, Georgia

Operating Authority: Columbus Water Works (CWW)

Permitted Capacity: 29.5 MGD

Current Average Flow: ~12-14 MGD

Population Served: ~206,000 (System-wide estimate)

Service Area: Northern Columbus and portions of Harris County/Fort Benning

Receiving Water Body: Chattahoochee River

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NPDES Permit Number: GA0020516

System Distinction: Integrated with North Highlands CSO Wet Weather Facility

TARGET AUDIENCE

• Municipal consulting engineers evaluating wet-weather flow integration.
• Wastewater treatment plant operators and asset managers.
• Regulatory officials tracking Chattahoochee River compliance.
• Engineering firms pursuing capital improvement projects in the Southeast.
• Researchers studying Combined Sewer Overflow (CSO) abatement strategies.

1. INTRODUCTION

The North Columbus Water Resources Facility (NCWRF) serves as a cornerstone of the Columbus Water Works (CWW) wastewater infrastructure, a system widely recognized as a national model for effective Combined Sewer Overflow (CSO) management. Located along the banks of the Chattahoochee River, this facility operates in tandem with the North Highlands CSO infrastructure to manage both continuous sanitary flow and high-volume wet-weather events. With a permitted capacity of 29.5 million gallons per day (MGD), the facility plays a critical role in protecting the water quality of the middle Chattahoochee basin.

Columbus Water Works has distinguished itself through the early adoption of advanced regulatory strategies and innovative biosolids management. The NCWRF functions not only as a conventional biological treatment plant but also as a critical hydraulic node in a complex collection system that mitigates untreated discharges. Following significant investments in the late 1990s and continuous capital improvements under the “One Water” management philosophy, the facility ensures compliance with strict Georgia Environmental Protection Division (EPD) standards while supporting the economic expansion of the Muscogee County region.

2. FACILITY OVERVIEW

A. Service Area & Coverage

The NCWRF services the northern sector of Muscogee County, capturing flows from residential neighborhoods, commercial corridors along Veterans Parkway, and light industrial zones. The collection system is a hybrid of separated sanitary sewers and legacy combined sewers (CSO), necessitating a highly responsive treatment strategy. The system includes extensive interceptor sewers that run parallel to the river, utilizing gravity to convey flows to the low-lying treatment site. The service area is characterized by undulating terrain, requiring a network of lift stations to convey wastewater from outlying subdivisions to the main interceptors.

B. Operational Capacity

The plant is permitted for a maximum monthly average flow of 29.5 MGD. Historically, the facility operates at approximately 40-50% of its hydraulic design capacity during dry weather, providing significant buffer for diurnal peaks and future regional growth. However, during significant precipitation events, the hydraulic loading increases rapidly due to Inflow and Infiltration (I&I) and the combined sewer network. The facility is designed to handle peak hourly flows significantly higher than the average design, diverting excess combined sewage to the dedicated North Highlands CSO treatment train when hydraulic capacities are exceeded.

C. Discharge & Compliance

Treated effluent is discharged into the Chattahoochee River, a water body designated for fishing, recreation, and drinking water supply downstream. The discharge is regulated under the National Pollutant Discharge Elimination System (NPDES) administered by the Georgia EPD. The facility operates under strict limits for Carbonaceous Biochemical Oxygen Demand (CBOD), Total Suspended Solids (TSS), Ammonia-Nitrogen, and Fecal Coliform. Given the recreational use of the “Whitewater Columbus” course downstream, disinfection reliability is a paramount compliance parameter.

3. TREATMENT PROCESS

The North Columbus Water Resources Facility utilizes a conventional activated sludge process with anaerobic selection zones to ensure robust biological treatment and nutrient reduction. The site is unique in that it houses both the continuous Water Reclamation Facility (WRF) and components of the wet-weather management system.

A. PRELIMINARY TREATMENT

Influent wastewater enters the headworks where it undergoes physical separation. Large debris is removed via mechanical bar screens (typically <6mm spacing) to protect downstream pumps. Grit removal follows, utilizing vortex grit separators to remove inorganic solids (sand, gravel) which are washed and dewatered for landfill disposal. This stage includes flow metering (Parshall flumes or mag meters) to determine pacing for downstream chemical feeds.

B. PRIMARY CLARIFICATION

Following headworks, flow enters 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 significantly reduces the organic load (BOD) sent to the biological reactors, improving energy efficiency in the secondary stage.

C. SECONDARY TREATMENT (Activated Sludge)

The core treatment occurs in the aeration basins. The facility utilizes a specific configuration of the Activated Sludge process:

• Selector Zones: Anoxic/Anaerobic zones at the front of the basins promote the growth of floc-forming bacteria over filamentous organisms, preventing sludge bulking and enabling biological phosphorus uptake.
• Aeration: Fine bubble diffusion systems provide oxygen for aerobic bacteria to metabolize dissolved organic matter and convert ammonia to nitrate (nitrification). Airflow is modulated via Variable Frequency Drive (VFD) blowers controlled by dissolved oxygen (DO) probes.
• Secondary Clarification: Mixed liquor flows to circular secondary clarifiers where biological floc settles. Settled biomass is returned to the aeration basins as Return Activated Sludge (RAS), while excess biomass is wasted (WAS) to solids handling.

D. TERTIARY FILTRATION

To meet stringent effluent limits, particularly for suspended solids and associated nutrients, the facility employs tertiary deep-bed granular media filters (or equivalent cloth media technology in recent retrofits). This polishing step ensures turbidity levels remain low, maximizing the efficacy of the subsequent disinfection process.

E. DISINFECTION

Historically, chlorination followed by dechlorination (using sodium bisulfite or sulfur dioxide) was the standard. However, CWW has progressively moved towards Ultraviolet (UV) disinfection across its assets to eliminate chemical handling hazards and reduce disinfection byproducts (DBPs) in the receiving water. The effluent passes through channelized UV banks where DNA of pathogenic organisms is disrupted, rendering them inert before discharge to the Chattahoochee River.

F. SOLIDS HANDLING & BIOSOLIDS STRATEGY

The NCWRF is integrated into CWW’s regional biosolids strategy. Solids handling at the North plant typically involves:

• Thickening: Primary sludge and Waste Activated Sludge (WAS) are thickened (often via gravity belt thickeners or rotary drums) to reduce volume.
• Regional Processing: CWW is famous for the Columbus Biosolids Flow-Through Thermophilic Pasteurization (CBFTTP) process. Thickened solids from the North Columbus facility are generally pumped or transported to the larger South Columbus Water Resources Facility (SCWRF) for digestion.
• Reuse: The processed biosolids (Class A EQ) are marketed as “Columbus Earth Helper,” a soil amendment used in agriculture and landscaping, achieving 100% beneficial reuse.

G. WET WEATHER / CSO INTEGRATION (North Highlands)

Distinct from the biological plant, the North Highlands CSO facility activates during heavy rain. It employs:

• Screening: Coarse and fine screens to remove floatables.
• Vortex Separation: High-rate physical separation of solids.
• Chemical Disinfection: High-dose chlorination (often sodium hypochlorite) with rapid mixing to treat bacteria in the combined flow before discharge.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The facility is situated on a footprint constrained by the Chattahoochee River to the west and urban development to the east. The site layout is linear, maximizing hydraulic efficiency. Architecture is utilitarian industrial, with recent improvements to administration buildings to support SCADA upgrades and operator comfort.

B. Energy Systems

As part of CWW’s sustainability initiatives, the facility has undergone energy audits to optimize aeration efficiency—typically the largest energy consumer. VFDs are installed on major prime movers (influent pumps, RAS/WAS pumps, blowers). While biogas generation occurs primarily at the South plant, the North facility benefits from grid-based power with backup diesel generation capacity sufficient to run critical treatment processes during outages.

C. Odor Control

Given the proximity to the Chattahoochee RiverWalk and commercial areas, odor control is a priority. The headworks and primary clarifier weirs are covered and ventilated to chemical scrubbers (wet scrubbers using caustic/bleach) or biological treatment units to treat hydrogen sulfide (H2S) before air release.

5. RECENT UPGRADES & MAJOR PROJECTS

Columbus Water Works maintains a robust Capital Improvement Plan (CIP) funded through revenue bonds and Georgia Environmental Finance Authority (GEFA) loans.

Integrated Master Plan Implementation (Ongoing)

Scope: Comprehensive assessment and rehabilitation of aging infrastructure across both North and South facilities.
Key Elements: Replacement of aging electrical switchgear, SCADA system migration to Rockwell/Allen-Bradley platforms, and concrete rehabilitation of aeration basins.

River Crossing & Interceptor Rehabilitation (2018-2023)

Project Budget: ~$15 – $20 Million (System-wide allocation)
Technical Highlights: Cured-In-Place Pipe (CIPP) lining of major interceptors feeding the North facility. This project was critical to reducing Inflow and Infiltration (I&I), thereby stabilizing the hydraulic load to the plant and reducing the activation frequency of the CSO facility.
Drivers: Asset management and I&I reduction.

Advanced Metering Infrastructure (AMI) Integration

While primarily a distribution project, the integration of AMI data allows plant operators to better predict diurnal flow patterns and detect system leaks or unauthorized discharges that could impact the biological process at the North plant.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

CSO Consent Decree: CWW operates under a historical understanding and proactive management regarding CSOs. The North Highlands CSO facility allows CWW to meet the “Nine Minimum Controls” and Long-Term Control Plan (LTCP) requirements by treating combined sewage rather than allowing raw bypasses.

Effluent Quality: The NCWRF consistently achieves high compliance rates.

• BOD5: Typically < 5.0 mg/L (well below permitted limits).
• TSS: Typically < 5.0 mg/L.
• Ammonia: Near-complete nitrification is achieved year-round.

Watershed Protection: The facility participates in the Middle Chattahoochee monitoring program, ensuring that discharge does not degrade the dissolved oxygen sag curve of the river.

7. OPERATIONAL EXCELLENCE

CWW is an active member of the Water Environment Federation (WEF) and the Georgia Association of Water Professionals (GAWP). The North Columbus facility is staffed by Class I and Class II certified operators. The utility utilizes a computerized maintenance management system (CMMS), likely Maximo or Cityworks, to schedule preventative maintenance on rotating assemblies and instrumentation.

The facility is also a testing ground for process optimization, balancing the biological health of the activated sludge against the chaotic hydraulic regime introduced by the region’s intense thunderstorms.

8. CHALLENGES & FUTURE PLANNING

A. Aging Infrastructure

Like many plants commissioned or significantly expanded in the Clean Water Act era (1970s-80s), the NCWRF faces the challenge of replacing mechanical equipment that is reaching the end of its useful life. Priority is placed on headworks reliability and clarifier drive mechanisms.

B. Emerging Contaminants

CWW is proactively monitoring regulatory discussions regarding PFAS (Per- and polyfluoroalkyl substances). While no current limits are enforced on the effluent, future regulations may require advanced treatment upgrades such as Granular Activated Carbon (GAC) or membrane retrofits.

C. Climate Resilience

Located in a river valley, the facility must plan for increased flood risk. Future planning includes hardening of electrical substations and raising critical control panels above the 500-year flood elevation.

10. TECHNICAL SPECIFICATIONS SUMMARY

12. FAQ SECTION

Technical Questions

1. What is the difference between the NCWRF and the North Highlands CSO facility?
The NCWRF is a biological wastewater treatment plant operating 24/7 to treat sanitary sewage. The North Highlands CSO facility is a wet-weather facility located nearby that only activates during heavy rain events to treat combined sewage via physical screening and chemical disinfection before discharge.

2. Does the North Columbus facility utilize anaerobic digestion?
Generally, no. The North facility thickens sludge and transports it to the South Columbus Water Resources Facility, which houses the centralized Cambi/CBFTTP digestion system for biogas production and Class A biosolids generation.

3. Is nutrient removal required at this facility?
Yes. The plant operates to remove ammonia (nitrification) and utilizes selector zones to encourage biological phosphorus uptake, although chemical precipitation (Alum/Ferric) may be used as a backup to meet river discharge limits.

Public Interest Questions

4. Is the discharge safe for the Chattahoochee River?
Yes. The effluent is treated to a level that meets or exceeds all state and federal standards for protection of aquatic life and recreational contact.

5. Who operates the facility?
The facility is owned and operated by Columbus Water Works, a public utility serving the Columbus, Georgia region.