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How San Jose Recycles Water: Inside the Silicon Valley Advanced Water Purification Center
- Saved By Nature
- Feb 16
- 11 min read
Updated: Feb 20
Quick Answer: How Does Silicon Valley Recycle Wastewater?
The San Jose-Santa Clara Regional Wastewater Facility (RWF) processes 110 million gallons of wastewater daily from 1.4 million residents across eight cities. The adjacent Silicon Valley Advanced Water Purification Center then applies a three-stage process—microfiltration, reverse osmosis, and ultraviolet light treatment—producing water 99%+ purified. This advanced recycled water reduces Santa Clara County's dependence on Sierra Nevada snowmelt imports while protecting South Bay wetlands and wildlife habitats.
Introduction: Silicon Valley's Water Recycling Infrastructure
The San Jose-Santa Clara Regional Wastewater Facility (RWF) and Silicon Valley Advanced Water Purification Center (WPC) are part of a complex water infrastructure owned and operated by Santa Clara Valley Water District (SCVWD). Founded in 1929, SCVWD mobilized to provide safe, clean water, flood protection, and stewardship of streams. The District manages 10 reservoirs and operates three water treatment plants that clean and disinfect 220 million gallons a day of drinking water from imported water and four local reservoirs.
The RWF plant accounts for 110 million gallons a day serving 1.4 million residents and 17,000 business-related sewer connections in the cities of San Jose, Santa Clara, Milpitas, Cupertino, Campbell, Los Gatos, Monte Sereno, and Saratoga. Santa Clara Valley Water District's water infrastructure includes a $54 million dollar investment in the innovative Silicon Valley Advanced Water Purification Center (WPC), with goals to expand recycled water to make up for 10% of the county's water demand.
Advancements at the Silicon Valley Advanced Water Purification Center make our local community less dependent on snowmelt from the Sierra Nevada that makes its way to the Sacramento–San Joaquin Delta before being imported to Santa Clara County treatment plants or aquifers—accounting for half our water supply. The federal government determines how much Sierra Nevada water we receive annually. The additional benefits of investing in the Silicon Valley Advanced Water Purification Center include replenishing aquifers with purified water for drinking and alleviating infrastructure damage caused by land subsidence.
Understanding how Silicon Valley treats and recycles water connects directly to environmental conservation—the same Bay Area ecosystems that depend on clean water discharge are explored through Saved By Nature's👉🏻 guided nature programs where participants observe the wildlife and wetlands downstream from these facilities.
History and Background of Silicon Valley Wastewater Treatment
From Untreated Sewage to Advanced Purification
Water quality in Santa Clara County before wastewater treatment plants was unsanitary. Before "advanced purification centers," people discarded sewage on streets and into local waterways. It wasn't until the 1880s that the City of San Jose built a meager sewage system to deliver untreated wastewater to the Bay. In the 1940s, indoor plumbing became more popular, generating more wastewater and leading to the passage of the federal Water Pollution Control Act of 1948.
By 1950 Santa Clara County implemented two water systems for stormwater and wastewater to reduce the amount of water requiring treatment. In 1964 the RWF incorporated secondary treatment to meet state regulations and accommodate a growing population. The Clean Water Act enacted in 1972, aimed at limiting and regulating pollution, forced the RWF to expand again—beginning to include tertiary treatment to meet CWA standards. Motivated by population growth and the need to conserve water, the South Bay Water Recycling facility was constructed in 1998, leading the way to a brighter sustainable future.
What Pollutants Does the San Jose Wastewater Facility Remove?
Residential Pollutants
The pollutants directed to the San Jose-Santa Clara Regional Wastewater Facility are byproducts of human activity. Ideally only feces, urine, and toilet paper are supposed to enter the toilet, but foreign objects and chemicals—including baby wipes, cigarette butts, dental floss, and pharmaceuticals—make their way to the RWF where most are removed. Trace elements of pharmaceuticals are left behind and released into the Bay. Cooking grease, oils, and fats also enter the system through kitchen sinks, clogging pipes and causing sewer overflows.
In 2014, the facility hauled 447 tons of grit, 501 tons of grease, and 607 tons of screenings—a total of over 1,500 tons of pollutants removed from our regional water supply in a single year.
Industrial Pollutants and Priority Monitoring
In addition to serving residents, the RWF maintains 17,000 main connections to businesses serving industries including food service, automotive, metal finishing, photo processing, and manufacturing.
The RWF monitors six priority pollutants: copper, nickel, cyanide, dioxin, indeno (1,2,3-cd) pyrene, and mercury. Additionally, six priority pollutant metals are tracked—arsenic, cadmium, chromium, selenium, silver, zinc, and lead—plus non-priority metals such as antimony, beryllium, and thallium. Receiving water's dissolved oxygen level cannot fall below 5.0 mg/L due to effluent discharges, protecting South Bay aquatic life.
One of the facility's core goals is to protect the health, environment, and economy of the South Bay by cleaning wastewater to near-drinking water standards before discharging it into the Bay—directly benefiting the wildlife and wetlands that 👉🏻 upcoming nature walks explore throughout the region.
San Jose-Santa Clara Regional Wastewater Facility: How It Works
Facility Overview and Scale
The City of San Jose built the original wastewater facility in 1956 and has since operated it 24 hours a day, 7 days a week. In 1959, the City of Santa Clara helped fund upgrades, gaining approximately 20% ownership. Operating on an $80 million annual budget overseen by San Jose and Santa Clara city councils, the RWF employs 200 employees and is regulated by both the Regional Water Quality Control Board and the Bay Area Air Quality Management District.
Buffered by RWF-managed bay lands, the 175-acre operations site contains about 4 miles of tunnels holding various valves, engines, and infrastructure. The plant has the capacity to take in and process 167 million gallons of water a day but on average processes 110 million gallons daily. The RWF boasts a 12,000 square-foot award-winning laboratory employing 20 technicians, chemists, and microbiologists, conducting 5,000 tests monthly to ensure proper treatment and compliance for both RWF and industrial dischargers.
The Three-Stage Treatment Process
After wastewater enters the San José–Santa Clara Regional Wastewater Facility it undergoes a three-step treatment process to remove solids, pollutants, and pathogenic bacteria. Machinery and gravity separate solids from the wastewater. Added bacteria clean water pollutants before the flow enters the advanced filter process. The treatment process produces water that is 99% purified before discharge into the Bay.
Stage 1 – Headworks (Pretreatment)
The entrance point of wastewater (influent) where heavy-duty rotating bars pull out large debris. The headworks structure was built to avoid accidental sewage spills due to mechanical malfunction, earthquakes, or other unexpected events. Berms and other protections surround the system to prevent sewage from entering the Bay.
Stage 2 – Primary Tanks
This 24-hour physical process removes about 50% of wastewater contaminants. In large tanks, the flow is slowed to allow gravity to separate large particles, mimicking the natural processes of creeks and rivers where sediments settle to the bottom. Fiberglass bars, or flights, skim off fats, oils, and grease while settled solid particles are moved into the digesters.
Stage 3 – Digesters
Pollutants and solid material removed during treatment are separated in digester tanks. It takes 25 to 30 days for anaerobic bacteria to stabilize unwanted material and reduce pathogens. Digesters produce methane gas that meets 35% of the WPC's energy needs—a significant sustainability achievement for a facility of this scale.
Secondary Treatment
Aeration
Aeration is a biological process that produces 95% clean water by pumping air into the flow. The oxygen-rich (aerobic) environment nurtures the growth of naturally-occurring aerobic bacteria that consume solids.
Clarifiers
After aeration, secondary wastewater is slowed in a set of 1-million gallon clarifier tanks to allow aerobic bacteria to settle. Treated water remains in the clarifiers for one to three hours. Some bacteria are sent back to the aeration tanks to repeat the process.
Tertiary Treatment and Outfall
Clarified wastewater is filtered and chlorinated in tertiary filtration, becoming 99% clean. The chlorine is neutralized before water is discharged to prevent harm to aquatic life.
After tertiary treatment, about 90% of the treated water is piped to the outfall channel, flowing to Artesian Slough, through Coyote Creek, and eventually into the wetlands of the 30,000-acre Don Edwards–San Francisco Bay National Wildlife Refuge. Because of the outfall channel's proximity, many birds and fish—including striped bass, largemouth bass, and Chinook salmon—are found here.
Of the 110 million gallons treated daily, 13% is sent to South Bay Water Recycling and used to irrigate food crops, parks, schools, golf courses, street medians, and business park landscaping—an annual average of 14 million gallons a day of recycled water reuse.
The byproduct of RWF's water treatment process is sludge, pumped to 11 anaerobic 1-million gallon digester tanks where methane is produced and captured to meet about 35% of RWF energy needs. After about 30 days, the sludge is transferred to open lagoons to dry and become biosolids—an average of 45,000 tons produced annually and used as alternative daily cover for landfills.
Silicon Valley Advanced Water Purification Center: Three-Stage Process
Facility Overview
The Silicon Valley Advanced Water Purification Center represents a landmark achievement in regional water sustainability. Santa Clara Valley Water District partnered with the City of San Jose and Santa Clara to meet the demand of Santa Clara County residents. The facility cost $72 million to build and produces 8 million gallons a day of highly purified water that can be blended with recycled water from RWF—increasing its quality for more diverse usage.
After touring this facility firsthand, I was very impressed with how clean it was and the state-of-the-art technology on display. The purification center uses a three-step process—microfiltration, reverse osmosis, and ultraviolet light—that mimics the process of how nature cleans water.
Step 1 – Microfiltration
Microfiltration is the process where treated wastewater is pushed through filtration membranes made of thousands of very fine pores—1/300th the width of a human hair.
Bacteria, protozoa, solids, and some viruses are filtered out in this first stage, dramatically reducing contaminant loads before more advanced treatment begins.
Step 2 – Reverse Osmosis
The reverse osmosis process forces water using very high pressure (50–190 psi) through holes so small only H₂O molecules can fit through.
This removes salts, viruses, and most contaminants including pharmaceuticals, personal care products, and pesticides. Three 500-horsepower pumps boost pressure before two chemicals are added to eliminate scaling and protect the reverse osmosis membranes.
Step 3 – Ultraviolet Light Treatment
Now that the water is clean, ultraviolet light is used as an additional safety procedure to inactivate any remaining viruses and trace organic elements.
There are 6 UV trains, each having two vessels; each vessel holds 40 high-intensity UV bulbs—for a total of 480 high-intensity UV bulbs providing comprehensive sterilization.
Complete Purification System Flow
Four 200-horsepower intake pumps deliver 8 million gallons of water a day that has gone through two levels of treatment at the RWF. After microfiltration, water transfers to a 225,000-gallon stainless steel tank before flowing to reverse osmosis transfer pumps and cartridge filters. After reverse osmosis, a decarbonization process reduces CO₂ to prevent corrosion. UV sterilization then precedes transfer to a 2.25 million gallon stainless steel storage tank. From here, water is sent to the Transmission Pump Station for blending with tertiary-treated recycled water from RWF—then distributed through the South Bay Water Recycling system serving over 600 customers.
Environmental Impact and Future of Silicon Valley Water Recycling in San Jose
Protecting South Bay Wetlands and Wildlife
The RWF and WPC operations directly impact the ecological health of South Bay wetlands. Careful monitoring of effluent quality protects fragile anadromous fish species—including Chinook salmon—and the migratory birds that depend on the Don Edwards–San Francisco Bay National Wildlife Refuge. Maintaining healthy treated water discharge standards supports the biodiversity of one of California's most important coastal wetland ecosystems.
Limiting water releases into the Bay while maintaining water quality standards requires ongoing investment in advanced purification technology—a balance between municipal water needs and ecological preservation that defines Silicon Valley's water management approach.
Sustainability and Energy Recovery
The methane gas produced by RWF digester tanks meets approximately 35% of the facility's energy needs—a meaningful step toward operational sustainability for a facility processing 110 million gallons daily. Future investments in the advanced oxidation process would increase effectiveness in producing water that meets and exceeds State Water Board regulations, potentially enabling recycled water use for more diverse agricultural crops, groundwater recharge, and eventually direct potable use.
Economic Advantages Over Ocean Desalination
Investing in advanced water purification is less expensive and more sustainable than tapping the ocean through desalination, which requires enormous energy to pressurize saltwater during the reverse osmosis process. Recycled water purification leverages water already processed through municipal systems, dramatically reducing both energy costs and environmental impact compared to ocean-sourced alternatives.
Frequently Asked Questions About Silicon Valley Water Recycling
How much wastewater does San Jose process daily?
The San Jose-Santa Clara Regional Wastewater Facility processes an average of 110 million gallons of wastewater per day, with capacity to handle up to 167 million gallons daily. It serves 1.4 million residents and 17,000 business connections across eight cities including San Jose, Santa Clara, Milpitas, Cupertino, Campbell, Los Gatos, Monte Sereno, and Saratoga.
What is the Silicon Valley Advanced Water Purification Center?
The Silicon Valley Advanced Water Purification Center is a $72 million water recycling facility operated by Santa Clara Valley Water District in partnership with San Jose and Santa Clara. It produces 8 million gallons of highly purified water daily using microfiltration, reverse osmosis, and ultraviolet light treatment—three stages that remove virtually all contaminants including pharmaceuticals and trace chemicals.
How clean is the water after treatment at the Silicon Valley WPC?
After completing the three-stage purification process—microfiltration, reverse osmosis, and UV treatment—water is purified to levels exceeding drinking water standards in many categories. The combined RWF and WPC process achieves 99%+ purity, with the WPC designed to add an advanced oxidation process that will enable direct potable reuse in the future.
Where does San Jose's treated water go?
About 90% of treated water flows through the outfall channel to Artesian Slough, through Coyote Creek, and into the 30,000-acre Don Edwards–San Francisco Bay National Wildlife Refuge. Approximately 13% is sent to South Bay Water Recycling for irrigation of parks, schools, golf courses, and agricultural land—an average of 14 million gallons per day.
Does the wastewater facility produce energy?
Yes. Anaerobic digester tanks at the RWF produce methane gas as a byproduct of treating wastewater sludge. This captured methane meets approximately 35% of the facility's total energy needs, significantly reducing operational costs and environmental footprint for a facility running 24 hours a day, 7 days a week.
How does water recycling benefit San Jose's environment?
Water recycling reduces dependence on imported Sierra Nevada snowmelt (currently 50% of Santa Clara County's supply), replenishes local aquifers, prevents land subsidence, and reduces pollutant discharge into San Francisco Bay. Treated water supports wetland ecosystems at Don Edwards National Wildlife Refuge—critical habitat for Chinook salmon, migratory birds, and hundreds of native species.
What pharmaceuticals does the wastewater facility remove?
The RWF removes most pharmaceuticals through primary and secondary treatment, though trace elements may remain in discharged water. The Silicon Valley Advanced Water Purification Center's reverse osmosis and UV treatment processes remove pharmaceuticals, personal care products, pesticides, and hormones more comprehensively—making purified water suitable for expanded reuse applications including groundwater recharge.
How does San Jose wastewater treatment protect the Bay?
The RWF operates under strict NPDES Permit regulations controlling Biochemical Oxygen Demand (BOD), Total Suspended Solids (TSS), ammonia, and priority pollutants including copper, nickel, mercury, and cyanide. Receiving water dissolved oxygen levels cannot fall below 5.0 mg/L from effluent discharges, protecting aquatic life throughout South Bay and the Don Edwards Wildlife Refuge.
Conclusion: Water Recycling and Environmental Stewardship in Silicon Valley
As far as I can tell, the RWF and WPC have been doing a great job managing our wastewater while producing innovative engineering that efficiently supports over 1 million people. I applaud these facilities for their foresight and investment in the use of recycled water for a more sustainable future. The infrastructure to transport water from the WPC to the Campbell percolation ponds along Highway 17—estimated at $72 million and 7 years to build—would be a great investment, especially since the WPC plans to introduce an advanced oxidation process to increase effectiveness in producing water that meets and exceeds State Water Board regulations. This would be a game changer for our water future since recycled water could be used for more diverse agricultural crops, industry, groundwater recharge, and eventually drinking.
Understanding these water systems deepens appreciation for the interconnected nature of urban infrastructure and Bay Area ecology. The same wetlands receiving treated discharge from these facilities provide habitat for the wildlife and natural communities explored through Saved By Nature's 👉🏻 outdoor education programs—guided experiences connecting participants to the ecosystems that depend on thoughtful water management.
Discover upcoming programs exploring Bay Area conservation, watershed health, and environmental stewardship by checking our 👉🏻 upcoming events. Every step toward understanding our water systems is an investment in protecting the San Francisco Bay Area's remarkable natural heritage.
Written by Richard Tejeda
Founder & Executive Director of Saved By Nature
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