What if the rains don't return for a long time?
Water agencies such as Santa Clara Valley Regional Water District, known as Valley Water, have sounded the alarm for more than a year. Cutbacks in water usage, which they say will be necessary, are likely to become a reality by this summer, staff said during a San Francisco Public Utilities Commission (SFPUC) meeting last month. The SFPUC owns Hetch Hetchy reservoir, a major water source for local counties and cities.
But Valley Water is looking for ways to not only conserve but also reclaim the precious crystal-clear liquid. In December, the agency's board of directors approved an agreement to work with the city of Palo Alto to build an advanced water-purification facility in Palo Alto. The 6.4-acre plant would be located at the old Los Altos Regional Wastewater Plant at the eastern end of San Antonio Road.
Wastewater from the separate Palo Alto Regional Water Quality Control Plant on Embarcadero Way would flow into the new facility, which would purify it to a usable cleanliness. The recycled water would be an additional source for irrigation, so-called "purple pipe" water that is used in industry and construction projects, and in agriculture. The plant would double the district's current supply of recycled water from the current 5% to 10% of its total water portfolio, the district said.
What's more, the water from the purification plant — millions of gallons of it — could be used for drinking after a little chemical tweaking and the state's approval.
Valley Water already has a similar 5-acre facility in San Jose. The Silicon Valley Advanced Water Purification Center currently cleans 10% of the water coming out of the nearby San Jose-Santa Clara Regional Wastewater Facility. The purified but non-potable water is used at 800 companies, including businesses at Levi Stadium and PayPal Park, for construction projects to keep dust down, and for irrigation and agriculture, said Gina Adriano, public information representative for the water district.
"This is the future of how to get water into our county. It's much more sustainable," Gary Kremen, Valley Water board member, said during a recent tour of the San Jose plant.
If the thought of drinking sewage water is a turnoff, consider this: By the time the purification plant strains, cleans and disinfects the wastewater, it contains no viruses, protozoa, bacteria or dangerous chemical contaminants. It also has fewer particles than Santa Clara County's regular tap water: 40 mg/Liter compared to 250 mg/Liter, according to Valley Water data.
From toilet to tap
The journey from mean water to clean water begins at the nearby San Jose-Santa Clara Wastewater Facility, which can treat up to 100 million gallons per day. The wastewater goes through three cycles of cleaning and disinfecting, Adriano said.
Most of this treated wastewater is sent to San Francisco Bay or is used as "purple pipe" water for landscapes and businesses. But up to 10 million gallons a day make their way in underground pipes to the purification center, resulting in about 8 million gallons of clean water each day, Adriano said.
A giant, 2.25-million-gallon metal holding tank towers over the home base of the Silicon Valley Advanced Water Purification Center, which opened in 2014 at the edge of the southernmost tip of the baylands between State Route 237 and Interstate 880.
A labyrinth of pipes and intake pumps receive the wastewater, which is the color of weak tea, and pressurize it to 40 pounds per square inch, or psi. The 40 pounds psi is the equivalent of forcing the water through an area about the diameter of a quarter.
Water first passes through four stainless steel mesh screens, which remove solid particles that are 300 microns or larger. Every 30 minutes a reverse flow flushes the screens, which are back-washed on the opposite side, sending the trapped particles back to the treatment plant.
Then the fun part begins.
"If you're a nerd, this is just the coolest thing ever," Kremen said as he entered the microfiltration room.
Inside a large warehouse, 896 vertical microfilter vessels reach nearly from floor to ceiling. Each contains 6,300 tiny straw-like tubes that filter out dissolved solids, protozoa, bacteria and large viruses bigger than 0.1 microns, or about 300 times smaller than the width of a human hair, according to the district.
The particles cling to the walls of each strand while the cleaned water passes through tiny holes at the center of each tube.
The water continues its journey to the 250,000-gallon inter-process tank located outside of the building, which helps regulate the pressure flow. An anti-scaling agent is added to prevent buildup of any microscopic matter in the next stage: reverse osmosis.
"It's like a spa for water. It gets pampered," Kremen said.
As the water is sent back into the warehouse, three reverse osmosis pumps raise the water pressure to 140 psi to help force the water through 240 reverse osmosis cartridges. The water is pushed through long, horizontal tubes containing rolls of special plastic membrane sheets in 1,000 layers, Adriano said.
The thin membranes allow the water to pass through while trapping compounds based on their size, shape and electrical charge. Contaminants larger than water molecules don't pass through, including most chemical contaminants, salt and organic compounds, small viruses and all remaining microorganisms, Adriano said.
While the clean water flows out of the vessels, the remaining water, contaminated with salt and other substances, flows out another outlet to start the process all over again, thus enabling more water to be recovered.
About 82% of all the original water becomes purified water, Adriano said.
But the water still has a way to go. Sent to two towering decarbonation tanks, it gets the Wiffle ball treatment. The towers contain 53,000 plastic super-frame balls, which look much like Wiffle balls, that remove carbon dioxide and reduce the water's acidity, which can corrode the water system.
The surface area of all the balls is equivalent to the size of an American football field, according to Valley Water. In a process similar to how soda in an open can loses its carbonation, the ball surfaces strip carbon dioxide from the water. While the water pours down into the lower part of the towers, the CO2 dissipates from the top.
Finally, ultraviolet light is used to turn water from pure into ultra-pure. The water is exposed to 40 high-intensity UV bulbs in 12 UV light reactors. After 30 seconds, the light has broken down any remaining pathogen DNA so it can't replicate. The exposure to this light is 20,000 times more effective than boiling water, according to Valley Water.
At the Palo Alto plant, testing of the water will ensure that chemical contaminants aren't present, Kremen said.
The purified water would be exported by a new 20-mile pipeline to existing percolation ponds on a 70-acre site in Campbell where it would seep down to recharge the underground water aquifer. Such water is known as indirect potable water, since it would be pumped up from wells before it is treated at a drinking water treatment plant, Kremen said.
To get recycled water to the drinking water state, Valley Water plans to add another step to the purification plant — advanced oxidation technology, which combines the UV light treatment and hydrogen peroxide. The process destroys all organic compounds, including those from pharmaceuticals, pesticides and personal-care products that might have been missed by other processes. The water would then meet the state's Division of Drinking Water's regulations for using purified water as a direct drinking source, so it will either go into the aquifer or be blended with other sources of water, which could be sent through water pipes directly to homes and businesses.
The future of drinking water?
Thirty percent of Valley Water's supply comes from rainfall and 70% from Hetch Hetchy, state and federal water programs. Those sources are slowly drying up and are predicted to become increasingly limited in the next decades.
"It's getting harder and harder to get water into Santa Clara Valley" from outside sources, Kremen said.
Half of the reservoir rainwater storage for Santa Clara County is also out of commission. Anderson Reservoir currently has only 4% capacity, according to current district data, due to mandated seismic retrofitting. It won't return to full capacity for at least a decade, Kremen said.
To offset some of the shortfall, recycled water must become more than a drop in the bucket. The district wants to increase its recycled water capacity from the current 5% to 20% of its supply by 2028, according to its 2021 Countywide Water Reuse Master Plan.
In Palo Alto, new pipes will need to be built along the U.S. Highway 101 on the east side to connect the two water plants. The purified water would be sent to Los Gatos Percolation Ponds in Campbell in the Santa Cruz Mountains near state routes 85 and 17, which would feed the water into the gravel of a deep underground aquifer.
The price tag for the project buildout, including the pipeline to Los Gatos/Campbell, isn't cheap. Capital costs are an estimated $600 million, Kremen said. The district is looking to obtain low-interest loans, such as those offered under the federal Water Infrastructure Finance and Innovation Act, the Clean Water State Revolving Fund Loan Program, the Infrastructure State Revolving Fund Loan Program, and state and federal reclamation and water recycling construction grants.
Funding could also come from the Department of Water Resources and State Water Resources Control Board, which received a share of an additional $22.5 million allocated for water and drought resilience that the state announced on March 13.
The majority of the funding, though, would come from a public/private partnership between the water district and a private contractor, who would pay for most of the costs to build and operate the facility. The district would pay a flat rate for the purified water and would buy back the facility at a low cost after 25 to 30 years, Kremen said. A third-party contractor is currently being considered.
The new facility will produce nearly as much purified water as the Silicon Valley Plant in San Jose, Valley Water said.
The cities of Palo Alto and Mountain View would have a first right to the potable groundwater if there's a drinking-water shortage, Kremen said. The cities would pay a fee if they opt to use it, he added.
Catherine Elvert, Palo Alto's Utilities communications manager, said the city and water district are still negotiating the land-lease agreement. She didn't have an estimate for when a deal might be inked. In addition to the lease, Valley Water would also pay about $1 million a year to purchase the effluent from the Regional Water Quality Control Plant for purification. Palo Alto would receive about one-third of that sum, she said. Other cities that send wastewater to the regional plant would receive payment for their proportional shares. Mountain View would receive about half of the money, Elvert said.
If all goes as planned, the facility could potentially be completed and operational by 2028.
Plans for the 6.4-acre purification plant would still leave room for another planned project on the 13-acre site, the Project Homekey emergency housing complex.
Will water rates increase?
Valley Water's purification facility will not impact Palo Alto water rates because the purified water will be used in other parts of the county to augment groundwater, which Palo Alto does not use, Elvert said.
On average, county residents who use the groundwater system would pay an additional $1 to $2 a month for the water, according to Valley Water's Countywide Water Reuse Master Plan.
"Santa Clara County is rapidly approaching a tipping point where purified water is cost competitive with other supplies," the Valley Water reuse master plan noted.
But though the water would not be used by Palo Alto residents, the city will benefit in numerous ways, including through the district's payments for Palo Alto's treated wastewater and through the land lease. For utilities customers, the new wastewater revenue would theoretically lead to lower sewer rates.
More broadly, the increased use of recycled water is a strategy that both Palo Alto and Mountain View fully support.
Palo Alto is currently developing its One Water Plan, an approach that integrates water resource planning with a comprehensive examination of non-potable water options such as captured stormwater and recycled water. The aim is to supplement and preserve the potable water supply.
The city's plan includes consideration of all potential non-potable water sources including the purification plant and the continued use and expansion of recycled water from the Regional Water Quality Control Plant, Elvert said.
Mountain View, meanwhile, wants to expand its current 4% recycled water usage by adding to its infrastructure to serve additional customers, according to the city's Recycled Water Feasibility Study Update from March 22. The city has also moved to standardize the use of recycled water: Its 2017 Dual Plumbing Ordinance also requires private commercial development greater than 25,000 square feet to include separate plumbing for recycled water uses such as toilets and landscaping as well as for drinking water.
The purification plant isn't the only piece of infrastructure that could boost the local supply of recycled water: Plans for a separate, smaller plant that could remove salt from treated water are also under development, following a December 2019 agreement between Palo Alto, Mountain View and Valley Water.
Currently, however, the entities are negotiating over the funding. In 2019, Valley Water committed $16 million to the project. The remaining costs for the desalination plant were to be paid for by Palo Alto (25%) and Mountain View (75%). But project costs have risen from $22.3 million to $51.4 million due to supply-chain issues, increased construction costs and modifications to address potential sea-level rise, according to a March 22 update to the Mountain View City Council.
In addition, during discussions with Palo Alto and Mountain View, Valley Water said that $12 million of its $16 million will come from refunds it had agreed to give the cities related to a tax that supported the State Water Project through Valley Water. The cities have voiced their objections, according to the Mountain View City Council report.
Kremen said by phone on Monday that the desalination operation might be added to the large purification facility as a way to potentially cut costs.
He took a pragmatic view of additional costs.
"What is the price of water if you don't have any? It's incalculable," he said.
This story contains 2448 words.
Stories older than 90 days are available only to subscribing members. Please help sustain quality local journalism by becoming a subscribing member today.
If you are already a subscriber, please log in so you can continue to enjoy unlimited access to stories and archives. Subscriptions start at $5 per month and may be cancelled at any time.