Washoe County Truckee Meadows Water Reclamation Facility Sparks

TARGET AUDIENCE

• Municipal consulting engineers evaluating biological nutrient removal (BNR) in cold climates.
• Wastewater treatment plant operators and managers focusing on strict nutrient limit compliance.
• Environmental regulators studying closed-basin river discharge standards.
• Equipment vendors researching advanced filtration and cogeneration specifications.
• University researchers interested in potable reuse (OneWater Nevada) and effluent management.

1. INTRODUCTION

The Truckee Meadows Water Reclamation Facility (TMWRF) serves as the primary wastewater treatment hub for the Reno-Sparks metropolitan area, treating an average of 28 million gallons daily (MGD) for approximately 450,000 residents. Jointly owned by the Cities of Reno and Sparks, and operated by the City of Sparks, this 44-MGD facility is technically renowned for operating under some of the most stringent discharge permits in the United States.

Because TMWRF discharges into the Truckee River—a sensitive, closed-basin system that terminates in Pyramid Lake (home to the endangered Cui-ui sucker fish)—the facility must achieve exceptional nutrient removal levels. It has long been a pioneer in Biological Nutrient Removal (BNR) and nitrogen management. Currently, TMWRF is at the forefront of the water industry’s shift toward circular economy principles, serving as a key site for the regional “OneWater Nevada” advanced water purification initiatives. Through continuous retrofitting and a robust Capital Improvement Plan, TMWRF remains a critical safeguard for Northern Nevada’s hydrologic health.

2. FACILITY OVERVIEW

A. Service Area & Coverage

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TMWRF provides regional wastewater treatment for a service area covering over 80 square miles. This includes the high-density urban cores of Reno and Sparks, as well as suburban expansion zones in Sun Valley and Spanish Springs. The collection system feeding the plant is complex, involving major interceptors from both cities. Demographics are mixed, with roughly 75% residential flow and significant contributions from the hospitality/gaming sector and a rapidly growing industrial base in the nearby Tahoe-Reno Industrial Center corridor (though some industrial flows are treated separately, TMWRF handles regional commercial growth).

B. Operational Capacity

The facility is rated for an annual average daily flow of 44.0 MGD. Historically, flows have stabilized around 26-30 MGD despite population growth, largely due to aggressive water conservation measures upstream and low-flow fixture implementation. However, peak wet weather flows can surge significantly due to infiltration and inflow (I/I) from older sections of the collection system. The plant manages hydraulic peaks exceeding 60 MGD via flow equalization basins. Capacity utilization currently sits at approximately 65%, providing runway for regional growth, though nutrient mass loading limits often present a tighter constraint than hydraulic capacity.

C. Discharge & Compliance

Treated effluent is discharged into the Truckee River or diverted for recycled water use. The receiving water body is highly sensitive; Pyramid Lake, the terminus of the Truckee River, is a nitrogen-limited terminal lake. Consequently, TMWRF operates under a strict Total Maximum Daily Load (TMDL) allocation. The facility consistently achieves effluent nitrogen levels below 2-3 mg/L and phosphorus levels below 0.2 mg/L, often exceeding permit requirements to generate “credit” for the regional water quality management program.

3. TREATMENT PROCESS

TMWRF employs a complex, multi-stage advanced treatment train designed specifically for high-efficiency Biological Nutrient Removal (BNR). The process has evolved from a conventional activated sludge plant to a sophisticated BNR facility.

A. PRELIMINARY TREATMENT

Raw influent enters the headworks via large interceptors where it undergoes screening and grit removal.

• Screening: Mechanically cleaned bar screens remove large debris (rags, plastics) to protect downstream pumps.
• Grit Removal: Aerated grit chambers decrease the velocity of the flow, allowing inorganic solids like sand and coffee grounds to settle while keeping organic matter in suspension.
• Odor Control: The headworks are enclosed and ventilated to chemical scrubbers to mitigate odors for the surrounding industrial/commercial neighbors.

B. PRIMARY TREATMENT

Flow enters rectangular primary sedimentation tanks. Here, gravity separation occurs:

• Settling: Heavy organic solids settle to the bottom as primary sludge.
• Scum Removal: Grease and oils float to the surface and are skimmed off.

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• Efficiency: Primary treatment typically removes 50-60% of Total Suspended Solids (TSS) and 30-40% of Biochemical Oxygen Demand (BOD), reducing the load on the secondary biological stage.

C. SECONDARY TREATMENT (Activated Sludge & BNR)

This is the core of TMWRF’s compliance strategy. The facility utilizes an Activated Sludge process configured for BNR to remove carbon, nitrogen, and phosphorus.

• Anaerobic Selectors: The initial zone is anaerobic to encourage the growth of Phosphate Accumulating Organisms (PAOs), facilitating biological phosphorus removal.
• Anoxic/Aerobic Zones: The mixed liquor passes through anoxic zones (for denitrification) and aerobic zones (for nitrification). Ammonia is converted to nitrate (nitrification), and nitrate is converted to nitrogen gas (denitrification).
• Nitrification Towers: Historically, TMWRF utilized distinct trickling filters (nitrification towers) to polish ammonia. While the plant has transitioned toward suspended growth BNR, these towers represent the facility’s legacy of aggressive nitrogen management.
• Clarification: Secondary clarifiers settle the biological floc. Return Activated Sludge (RAS) is sent back to the front of the biological process, while Waste Activated Sludge (WAS) is sent to solids handling.

D. TERTIARY TREATMENT

To meet the strict TSS and nutrient limits for the Truckee River, secondary effluent undergoes tertiary polishing:

• Coagulation/Flocculation: Chemicals (such as alum or polymer) are added to precipitate remaining phosphorus and bind fine particles.
• Filtration: The water passes through dual-media gravity filters (anthracite coal and sand). This step ensures effluent turbidity is consistently low (often < 1 NTU) and removes particulate phosphorus.

E. DISINFECTION

TMWRF utilizes chlorination for disinfection, followed by dechlorination to protect aquatic life.

• Chlorination: Sodium hypochlorite is injected into chlorine contact basins to pathogen inactivation.
• Dechlorination: Sodium bisulfite is added prior to discharge to neutralize residual chlorine, ensuring zero toxicity to the Truckee River ecosystem.

F. SOLIDS HANDLING

Solids processing is a major energy recovery component at TMWRF:

• Thickening: Primary sludge and WAS are thickened (using dissolved air flotation or gravity belts) to reduce volume.
• Anaerobic Digestion: Thickened sludge enters anaerobic digesters where it is stabilized at mesophilic temperatures (~98°F). This process reduces pathogen content and volatile solids.
• Dewatering: Digested sludge is dewatered using high-speed centrifuges to produce a “cake” with higher solids content.
• Disposal: The dewatered biosolids are trucked to the regional landfill, though evaluation of composting and land application is ongoing.

4. INFRASTRUCTURE & FACILITIES

A. Physical Plant

The site spans approximately 130 acres in the eastern industrial section of Sparks. The layout is dominated by the large rectangular aeration basins, the iconic nitrification towers, and the extensive solids handling complex. The site includes a fully accredited environmental laboratory that performs daily compliance testing and river monitoring.

B. Energy Systems & Cogeneration

TMWRF is a leader in energy recovery. The anaerobic digestion process produces methane-rich biogas.

• Cogeneration: The plant utilizes internal combustion cogeneration engines to convert biogas into electricity and heat.
• Energy Independence: These engines can generate a significant portion (often 30-50%) of the plant’s electrical demand.
• Heat Loop: Waste heat from the engines is captured to heat the digesters and facility buildings, closing the energy loop.

C. Odor Control

Given the proximity to the I-80 corridor and commercial developments, odor control is critical. The facility employs packed-tower wet scrubbers and biofilters at key generation points (headworks and solids handling). The SCADA system monitors differential pressure and chemical dosing to ensure continuous scrubbing efficiency.

5. RECENT UPGRADES & MAJOR PROJECTS

The Joint Coordinating Committee maintains an aggressive Capital Improvement Plan (CIP) to address aging infrastructure and evolving regulations.

OneWater Nevada (Advanced Purified Water)

While not a full-scale build-out at TMWRF yet, the facility hosts pilot/demonstration projects for OneWater Nevada. This regional initiative creates A+ advanced purified water. The demonstration proved that TMWRF effluent can be purified via Ozone-BAC (Biological Activated Carbon), UF (Ultrafiltration), and UV to meet drinking water standards, setting the stage for future indirect or direct potable reuse projects in the region.

6. REGULATORY COMPLIANCE & ENVIRONMENTAL PERFORMANCE

A. Permit Requirements

TMWRF operates under NPDES Permit NV0020150. The permit is characterized by:

• Nitrogen: Seasonal limits driven by the Truckee River TMDL. Total Nitrogen (TN) loads are strictly capped.
• Phosphorus: Total Phosphorus (TP) limits are among the lowest in the nation to prevent algal blooms in the river and Pyramid Lake.
• TDS (Total Dissolved Solids): A challenging parameter in the region due to closed-basin hydrology and geothermal activity.
• Thermal Load: Regulations on the temperature of the effluent to protect cold-water fish species (trout/salmonids).

B. Compliance History

TMWRF maintains a strong record of compliance. The facility has received multiple Gold and Silver Peak Performance Awards from NACWA (National Association of Clean Water Agencies). The plant’s ability to balance chemical usage with biological performance allows it to consistently meet nutrient targets despite variable influent loads.

7. OPERATIONAL EXCELLENCE

A. Staffing

The facility is staffed by approximately 60-70 full-time employees, including operations, maintenance, instrumentation/electrical, laboratory, and administration personnel. Operators are required to hold Nevada Department of Environmental Protection (NDEP) wastewater certifications, with senior staff holding Grade III and IV licenses.

B. Technology & Innovation

TMWRF utilizes a sophisticated SCADA system for real-time monitoring. The plant has been a testbed for nutrient removal technologies, including research into side-stream treatment (deammonification) to handle high-ammonia centrate from the dewatering process, thereby reducing the load on the main biological train.

8. CHALLENGES & FUTURE PLANNING

A. Current Challenges

• Total Dissolved Solids (TDS): As water is conserved and recycled, salts concentrate. TMWRF faces challenges in managing TDS without reverse osmosis, which creates brine disposal issues.
• Aging Infrastructure: Much of the plant was built in the 1980s. Concrete degradation in headworks and digesters requires constant rehabilitation.
• Chemical Costs: Rising costs of coagulants (alum/ferric) and methanol (for denitrification) drive the push for process optimization.

B. Future Planning

The regional wastewater master plan envisions TMWRF working in conjunction with satellite reclamation facilities. The “purple pipe” network is expanding, diverting more effluent to irrigation and industrial use (like the Tesla Gigafactory region), reducing thermal and nutrient loading to the river. Future capital projects focus heavily on electrical distribution upgrades, headworks rehabilitation, and further integration of Advanced Water Purification technologies.

9. COMMUNITY & REGIONAL IMPACT

TMWRF is the hydrologic kidney of the Truckee Meadows. By returning high-quality water to the Truckee River, it supports the flow required for recreation (kayaking/fishing) in downtown Reno and the ecological health of Pyramid Lake. The facility creates high-skilled jobs and supports the region’s rapid housing growth by ensuring sewer capacity is available. The plant also offers tours to engineering students from the University of Nevada, Reno (UNR), fostering the next generation of water professionals.

10. TECHNICAL SPECIFICATIONS SUMMARY

11. RELATED FACILITIES

• Reno-Stead Water Reclamation Facility: A smaller satellite plant (~2.0 MGD) serving the North Valleys area, utilizing MBR technology.
• South Truckee Meadows Water Reclamation Facility (STMWRF): Operated by Washoe County, serving the southern reaches of the valley.
• American Flat Road & Tahoe-Reno Industrial Center: Rapidly developing industrial water reclamation infrastructure connected regionally.

12. FAQ SECTION