Sustainability

2. Emissions from the Supply of Potable Water Operations in Washoe County (USCP Recommended)

0.03 MMT of CO2e | 33% of Water & Wastewater Emissions | <1% of overall emissions

Sources of MT CO2e for Potable Water Operations

Definition of Potable Water Operations Potable Water Operations deliver clean drinking water to members of the community.

Potable Water in Washoe County Four operators provide potable water to the Washoe County community. Truckee Meadows Water Authority (TMWA) is a not-for-profit, community-owned water utility serving more than 440,000 residents. Great Basin Water Company is a private water and wastewater utility provider delivering services to over 20,000 residential and commercial customers in the Cold Springs, Spanish Springs in Washoe County as well as Spring Creek (Elko County), and Pahrump (Nye County) communities. Finally, two General Improvement Districts (GIDs) provide water to their residents: Incline Village and Sun Valley. Incline Village GID is chartered to provide water, sewer, trash, and recreation services for the communities of Incline Village and Crystal Bay, Nevada in unincorporated Washoe County. Sun Valley GID is chartered to provide water, sewer, garbage, and recreation services throughout the community. The District owns and maintains an estimated 100 miles of water mains, 120 miles of sewer mains, two sewer vaults, several pressure reducing vaults and pumping stations, and nine water storage water tanks. The Gerlach GID provides water, disposal, and sewer services to the 125 residents of the community. For more about GIDs in Nevada, see the Glossary in Appendix 2. Together, these four operators process 30,076 million gallons of water each year.

GHG Inventory Methodology Emissions for potable water production are calculated based on electricity and natural gas use, as documented in E2 Energy Methodology. Operators’ energy use is listed below. In the Commercial Energy sector of this inventory, potable water GHG energy usage values are subtracted from the utility-provided total energy-use numbers to avoid double-counting.

3. Emissions from Wastewater Operations in Washoe County

0.06 MMT of CO2e | 67% of Water & Wastewater Emissions | <1% of overall emissions

Sources of MT CO2e for Wastewater Operations

Definition Wastewater, per the EPA, includes water that has constituents of human and / or animal metabolic (related to converting food and drink to energy in the body) wastes and water that has residuals from cooking, cleaning and / or bathing.

Wastewater Management in Washoe County Five organizations process wastewater in Washoe County. Truckee Meadows Water Reclamation Facility (TMWRF), has a permitted capacity of 44 million gallons / day. That capacity is shared between the cities of Reno and Sparks and portions are leased to the Sun Valley General Improvement District and Washoe County. Current flows into the facility average 30 million gallons / day. The facility (see an image in Figure 13) is located in the City of Sparks, which serves as the operating authority. City of Reno directs major capital improvements, and a Joint Coordinating Committee (JCC) includes representatives from Sparks, Reno, Washoe County, and Sun Valley General Improvement District (GID). TMWRF serves the central Truckee Meadows, including areas within the City of Reno, the City of Sparks, the Sun Valley General Improvement District, and portions of Washoe County that are within the Truckee Meadows and the Spanish Springs Valley. The sewer system transports wastewater flows from the Truckee Meadows Valley, Spanish Springs Valley, Sun Valley, Verdi / Truckee Canyon, and portions of the Golden Valley and Lemmon Valley hydrographic (river) basins.

Figure 13 TMWRF facility, via TMWRF website

The Reno-Stead Water Reclamation Facility (RSWRF) is a wastewater treatment and water reclamation facility meeting the latest design standards, instrumentation and process control technology, and energy and manpower efficiency to treat up to 2 million gallons per day of raw sewage, in compliance with stringent public health and water quality discharge standards. In 2021, RSWRF’s capacity was approximately 2 million gallons per day. The facility planned to expand its capacity to 4 million gallons per day by 2023. A large portion of the water recycled at RSWRF flows to Swan Lake, where it supports the Swan Lake Nature Study. During the irrigation season, recycled water from RSWRF is also used for irrigation at North Valleys Regional Park / Sports Complex, Sierra Sage Golf Course, The Lakes Apartments, and Mayor’s Park. RSWRF also has a Truck Fill Station in Reno for recycled water service customers.

The Washoe County Community Services Department Utility Team provides wastewater treatment to approximately 16,000 customers including some urban areas in Reno and Sparks. The Utility treats an average of 5 million gallons of wastewater per day at three regional wastewater plants and manages the recovery of reclaimed water and biosolids from these waste streams. The three regional wastewater plants are South Truckee Meadows Water Reclamation Facility (STMWRF), Cold Springs Water Reclamation Facility (CSWRF), and Lemmon Valley Water Reclamation Facility (LVWRF).

Incline Village GID Wastewater Reclamation Facility receives an average of 1.3 million gallons of wastewater daily. The collection and export system for wastewater includes: 100 miles of sewer pipelines, 18 pumping stations, a half million-gallon storage tank, and a twenty-mile export pipeline taking treated effluent water out of the Tahoe Basin for final disposal. The wastewater treatment plant processes and disinfects wastewater using conventional biological treatment processes and solids handling facilities. The wastewater treatment process from start to finish takes approximately 15 hours. The solids removed from the process are sent to Bentley Ranch for composting with other organic material. The export pipeline transports the plant’s secondary treated effluent to the IVGID wetlands in Douglas County.

The Gerlach GID has a small treatment plant south of the town. Influent waste flows through two, 1.4 acre facultative ponds in series, then empties into an evaporation basin. Nominal capacity is 20,000 gallons per day. In a facultative system, no energy is used.

And finally, some households and businesses, usually in suburban and rural areas, do not receive direct service from centralized wastewater treatment plants. These buildings depend on septic systems to treat and dispose relatively small volumes of wastewater. Septic systems treat wastewater from household plumbing fixtures (toilet, shower, laundry, etc) through both natural and technological processes, typically beginning with solids settling in a septic tank, and ending with wastewater treatment in the soil via the drainfield. This inventory estimates the population served by septic systems (57,472) by subtracting the operator-reported population served by wastewater treatment plants (427,641) from the 2021 NV State Demographer’s population statistic (485,113).

How wastewater treatment plants work Wastewater treatment plants clean sewage and water so they can be returned to the environment. First, large and small debris is removed. Next, organic matter, including carbon and nitrogen, is broken down and removed. Then, the wastewater is treated to remove phosphorus, nitrogen, and other nutrients, and it is disinfected. Finally, the solid sludge is treated and sent to landfill, and the clean water is returned to the environment.

Truckee Meadows Water Reclamation Facility (TMWRF) describes its specific process on its website: “TMWRF is a biological nutrient removal plant that uses separate nitrification and denitrification processes for nitrogen removal and biological and chemical processes for phosphorus removal. Reclaimed water is discharged to the Truckee River or is pumped to effluent (treated wastewater) reuse sites throughout the region. Solids are thickened, anaerobically digested, dewatered and hauled to the local landfill for disposal. The methane gas produced by solids digestion is used to generate the hot water which is used to heat many TMWRF’s buildings as well as run a 988 kilowatt cogeneration engine which reduces power costs for the facility by roughly 1/3.”

GHG Inventory Methodology

Wastewater emissions come from different stages of the treatment process. First, the energy used to run the facilities causes emissions. Second, emissions come from the processes of combusting (burning) and flaring wastewater gases. Third, emissions come from the process of removing nitrogen from the water. And fourth, combustion of solid waste causes emissions. Not all facilities in Washoe County use all of these processes.

Energy Use methodology Emissions for wastewater processes are calculated based on electricity and natural gas use, using the factor sets documented in E2, Energy Methodology. Operators’ energy use is listed above. To avoid double-counting, this inventory subtracts reported wastewater GHG energy use data from the utility-provided total energy-use data in the Commercial Energy section of this report.

Digester methodology Digestion is a process through which bacteria break down organic matter. This process is used on biosolids that are removed from wastewater.

Anaerobic digestion happens in the absence of oxygen in a vessel called a reactor. The process produces two outputs: biogas and digestate. Biogas is composed of a large percentage (50-75%) of methane (CH4) as well as carbon dioxide (CO2), hydrogen sulfide (H2S), water vapor, and trace amounts of other gases. Digestate is the residual material left after the digestion process. It is composed of liquid and solid portions.

Aerobic digesters, which operate in the presence of oxygen, produce non-combustible carbon dioxide gas, not methane. This process can also produce products like nitrate and phosphate.

TMWRF uses an anaerobic digester, and Washoe County uses an aerobic digester. Reno Stead, Incline Village, and Gerlach do not have digesters.

TMWRF combusts (burns) its methane gas (51%) and flares the remainder of the gas (49%). The exact methane destruction efficiency is not monitored, so this inventory assumes a destruction efficiency of 99.96%. The inventory uses the methane (CH4) emissions factor (0.0032 kg / MMBtu) and nitrogen emissions factor (0.00063 kg / MMBtu) to estimate the GHG impact of processing these gases. TMWRF recovers energy from this process and sends that energy to the electric grid; the facility uses heat from the process on-site.

Nitrification / denitrification methodology Nitrification and denitrification are processes used to clean wastewater. Nitrification is the biological oxidation (adding of oxygen) of ammonia (NH3) or ammonium (NH4+) in wastewater to create nitrite (NO2, then NO3). Denitrification is the process in which nitrate (NO3) is converted into nitrogen gas (N2) that goes back into the atmosphere, instead of polluting sensitive waterways. This inventory uses the emissions factor of 7 grams of N2O / person for the nitrification / denitrification process. The inventory then uses the N2O emissions factor of 0.005 kg N2O / kg N to measure the GHG impact of the daily nitrogen load in wastewater effluent. “Nitrogen load” is the amount of nitrogen discharged into a water body during a time period.

Methanol methodology Some wastewater treatment plants use methanol to assist with nitrogen removal. Methanol (CH3OH) is a type of alcohol that functions as a carbon source to accelerate the biodegradation of nitrogen. TMWRF is the only plant in Washoe County that uses methanol, and it uses 8.9 metric tons / day. This inventory applies an emissions factor of 1.096 CO2.

Solids Disposal methodology Some wastewater treatment plants combust their biosolids, causing emissions. None of the facilities in Washoe County do this. All of the biosolids are landfilled, and those emissions are captured in section E6, Solid Waste.

Septic – Fugitive Methane emissions methodology This inventory calculates methane emissions from septic users. Using population data, the inventory applies a methane generation rate of 0.09 kg BOD5 / person / day. “BOD” stands for “biochemical oxygen demand,” and BOD5 is an indirect measure of the biodegradable organic material present in water. The inventory then applies the methane emissions factor of 0.048213 MT CH4 / daily kg BOD5.

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