City Of Vancouver Bi County Wastewater Treatment Plant

1. INTRODUCTION

The Westside Wastewater Treatment Plant serves as the cornerstone of wastewater infrastructure for Southwest Washington, treating effluent for the City of Vancouver and portions of the Clark Regional Wastewater District. Situated on the north bank of the Columbia River, this facility is critical to the environmental health of the Pacific Northwest’s largest waterway. While owned and operated by the City of Vancouver, the plant functions as a regional asset, processing flows from a bi-jurisdictional service area that includes dense urban centers and rapidly growing suburban corridors.

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With a design maximum monthly flow of 28.3 MGD and a peak hydraulic capacity approaching 60 MGD, the Westside facility utilizes conventional activated sludge treatment paired with a highly specialized solids handling process: fluidized bed incineration. Recent capital investments exceeding $70 million have modernized the facility’s solids handling capabilities and electrical infrastructure, positioning the plant as a model of regulatory compliance and operational resilience in the face of regional population growth.

2. FACILITY OVERVIEW

A. Service Area & Coverage

The Westside WWTP operates within a unique regional framework. It receives influent from the City of Vancouver’s collection system (serving downtown and western neighborhoods) and the Clark Regional Wastewater District (CRWWD), which serves the unincorporated areas north and west of the city limits. This “bi-county” style partnership allows for economies of scale in treatment while maintaining distinct collection system management. The service area is characterized by a mix of established residential zones, the Port of Vancouver’s heavy industrial district, and expanding commercial corridors.

B. Operational Capacity

The facility is designed to handle significant hydraulic variations typical of the Pacific Northwest’s wet weather seasons.

• Design Average Flow: 28.3 MGD
• Peak Hour Flow: 60+ MGD
• BOD5 Loading Capacity: Approx. 68,000 lbs/day
• TSS Loading Capacity: Approx. 70,000 lbs/day

Historically, the plant operates at approximately 75-80% of its hydraulic capacity during dry months, with wet weather events utilizing equalization storage to manage peak inflows and prevent permit excursions.

C. Discharge & Compliance

Treated effluent is discharged into the Columbia River via a submerged outfall diffuser at River Mile 105. The plant operates under National Pollutant Discharge Elimination System (NPDES) Waste Discharge Permit No. WA0024350, administered by the Washington State Department of Ecology. The facility maintains a strong compliance record, consistently meeting strict limits for Carbonaceous Biochemical Oxygen Demand (CBOD), Total Suspended Solids (TSS), and pH, while navigating the complex thermal load regulations associated with Columbia River salmonid migration corridors.

3. TREATMENT PROCESS

A. PRELIMINARY TREATMENT

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Influent enters the plant through large interceptors where it undergoes rigorous preliminary treatment to protect downstream mechanical equipment.

• Screening: Mechanically cleaned bar screens remove rags, plastics, and large debris. The screenings are washed, compacted, and disposed of at a landfill.
• Grit Removal: Following screening, flow enters aerated grit chambers where velocity is reduced to allow inorganic solids (sand, gravel, coffee grounds) to settle. The grit is pumped out, classified, and dewatered for disposal.

B. PRIMARY TREATMENT

The Westside facility utilizes primary clarification to reduce the organic load on the biological system.

• Clarifiers: Flow is distributed to primary clarifiers (circular configuration).
• Efficiency: These units typically remove 50-60% of Suspended Solids and 30-35% of BOD through gravity settling.
• Scum Removal: Surface skimmers remove grease and oils, which are pumped to the solids handling train.

C. SECONDARY TREATMENT

The biological treatment stage utilizes a Conventional Activated Sludge process designed to oxidize remaining organic matter.

• Aeration Basins: The plant operates multiple aeration basins equipped with fine-bubble diffusers to maximize oxygen transfer efficiency. The basins maintain a mixed liquor suspended solids (MLSS) concentration optimized for CBOD removal.
• Secondary Clarifiers: Mixed liquor flows to secondary clarifiers where biological floc settles out. The clear supernatant overflows the weirs to disinfection.
• RAS/WAS: Return Activated Sludge (RAS) is pumped back to the aeration basins to maintain the biological population. Waste Activated Sludge (WAS) is thickened and sent to solids handling.

D. DISINFECTION

Unlike many modern facilities converting to UV, the Westside WWTP currently utilizes a chemical disinfection process, which remains effective for the high volumes treated.

• Chlorination: Chlorine gas (or hypochlorite) is injected into the effluent in chlorine contact basins (CCBs) to ensure pathogen inactivation (fecal coliform reduction).
• Dechlorination: Before discharge into the Columbia River, the effluent is dechlorinated using sulfur dioxide or sodium bisulfite to protect aquatic life, ensuring zero residual chlorine in the discharge.

E. SOLIDS HANDLING (Notable Feature)

The Westside plant is distinguished by its use of thermal reduction (incineration) for solids processing, a necessity given the high volume of solids and limited land application options in the immediate urban vicinity.

• Thickening: Primary sludge is gravity thickened; WAS is thickened using gravity belt thickeners or rotary drum thickeners.
• Digestion: The plant historically utilized anaerobic digestion, but recent upgrades have focused on preparing solids for autogenous combustion.
• Dewatering: Thickened sludge is dewatered using high-solids centrifuges to achieve a cake dryness sufficient for efficient incineration (typically 25-30% solids).
• Incineration: The facility recently commissioned a new Fluidized Bed Incinerator (FBI). This system suspends the sludge in a hot sand bed, ensuring complete combustion and meeting strict EPA sewage sludge incineration (SSI) air emissions standards. The resulting inert ash is landfilled.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The site is constrained by the Columbia River to the south and urban development to the north. The layout is linear, designed to move water via gravity where possible. Key structures include the Administration Building, Maintenance Shop, Process Control Center, and the distinctive stack of the solids incineration complex.

B. Energy Systems

Wastewater treatment is energy-intensive. The Westside plant consumes significant power for aeration and pumping.

• Heat Recovery: The new Fluidized Bed Incinerator includes heat recovery systems that pre-heat combustion air, significantly reducing the requirement for auxiliary fuel (natural gas).
• Efficiency: Variable Frequency Drives (VFDs) have been retrofitted on major pumps and blowers to match energy use with diurnal flow patterns.

C. Odor Control

Given the proximity to downtown Vancouver and commercial districts, odor control is paramount. The headworks and solids handling buildings are enclosed and vented through chemical scrubbers and carbon adsorption systems to treat hydrogen sulfide and mercaptans before releasing air to the atmosphere.

5. RECENT UPGRADES & MAJOR PROJECTS

Upcoming Projects (CIP)

Future planning includes the “Westside Liquid Stream Upgrade,” aiming to rehabilitate secondary clarifiers and upgrade aeration basin blower technologies to Turbo Blowers for enhanced energy efficiency. Additionally, seismic retrofitting of critical structures is planned to meet modern Cascadia Subduction Zone resilience standards.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

A. Permit Requirements

Under NPDES Permit WA0024350, the Westside WWTP adheres to the following primary limits (monthly average):

• CBOD5: 25 mg/L (and 85% removal)
• TSS: 30 mg/L (and 85% removal)
• pH: 6.0 – 9.0 Standard Units
• Fecal Coliform: 200/100 mL

B. Industrial Pretreatment

Because the service area includes the Port of Vancouver, the plant manages a robust Industrial Pretreatment Program. This program monitors and permits industrial dischargers (breweries, silicon wafer manufacturing, food processing) to prevent pass-through of toxic metals or slug loads that could upset the biological process.

7. OPERATIONAL EXCELLENCE

The facility is staffed 24/7/365 by a team of certified wastewater operators, industrial mechanics, and instrumentation technicians. The City of Vancouver maintains a high level of certification requirements, with lead operators typically holding Washington State Group III or IV certifications. The plant utilizes a robust SCADA system for real-time monitoring of dissolved oxygen levels, incinerator temperatures, and hydraulic loading.

8. TECHNICAL SPECIFICATIONS SUMMARY

9. FAQ SECTION

Technical Questions

1. Why does the Westside plant use incineration instead of land application?
Due to the high volume of solids produced and the urban density of the service area, hauling biosolids for land application is logistically challenging and carbon-intensive. The Fluidized Bed Incinerator allows for maximum volume reduction (reducing solids to inert ash) and energy recovery, making it the most viable option for this specific site.

2. Is the facility equipped for Nutrient Removal?
Currently, the NPDES permit for discharge into the Columbia River (a high-volume, cold water body) does not mandate stringent nitrogen or phosphorus removal limits comparable to facilities discharging into the Puget Sound or small tributaries. However, the City monitors nutrient levels for future planning.

3. How are industrial flows managed?
The City operates a Delegated Industrial Pretreatment Program. Significant Industrial Users (SIUs) must pretreat their waste to specific standards before discharging to the collection system to protect the plant’s biological processes.

General Interest

4. Does the plant smell?
Odor control is a top priority. The City uses chemical scrubbers and carbon filters to capture odors at the source (headworks and solids handling). While occasional odors may occur during maintenance, the system is designed to be a “good neighbor.”

5. Who pays for the treatment?
Operations are funded through sewer utility rates paid by residents and businesses in Vancouver, and through wholesale service agreements with the Clark Regional Wastewater District.