More severe droughts are looming. Could Santa Rosa’s pioneering water recycling program help stave off disaster?
Homes and businesses across central Sonoma County generated more than 5 billion gallons of wastewater last year, enough to fill more than 7,500 Olympic-sized swimming pools. That sewage flowed into Santa Rosa’s regional treatment plant south of Sebastopol, where it was cleaned up and nearly all of it put to a second use.
About 4 billion gallons of recycled water was pumped north from the Llano Road treatment plant in a 41-mile pipeline and up a steep slope into The Geysers geothermal fields southeast of Cloverdale. There it was injected into the ground to generate enough clean, renewable energy for about 100,000 North Bay households.
The system also sent 788 million gallons of recycled water to 61 farms covering 6,400 acres that produce milk, hay, grapes and vegetables, along with 386 million gallons for urban irrigation in Rohnert Park and Santa Rosa, the two largest cities in the wastewater system.
Every drop of the recycled irrigation water — safe for everything short of human consumption and sanitized to a degree that eliminates the COVID virus — replaces a drop of potable water from sources sure to be strained as California moves into its third year of worrisome drought.
But the state’s water future is daunting, and could pose a fundamental challenge to Santa Rosa’s recycling system, which was born out of controversy in the 1980s and is now hailed by state regulators as a win-win that safeguards local waterways — the Laguna de Santa Rosa and Russian River — previously used for discharge.
For water-stressed parts of California, where winter snowpack and rains are proving increasingly scarce or unreliable, recycled water is likely to prove a key source not just for irrigation but household and commercial use.
The warning signs are already apparent: State water regulators on Tuesday signaled plans to reduce or suspend diversions along the Russian River and its tributaries in Sonoma and Mendocino counties as early as June. The moves would likely affect fewer than the 1,800 water rights frozen last year in the face of dangerously low reservoir levels.
Long-range climate forecasts call for even more severe and persistent droughts, making existing surface and groundwater supplies more tenuous, while California’s latest long-term water strategy calls making greater use of recycled water.
“Recycled water is a sustainable, nearly drought-proof supply when used efficiently, and the total volume of water California recycles today could triple in the next decade,” the 2020 California Water Resilience Portfolio said.
The 141-page document was issued in response to Gov. Gavin Newsom’s executive order in 2019 calling for recommendations “to enable water security for all Californians.”
It also called for streamlining regulations to expand use of nonpotable recycled water while “protecting food safety and the environment.”
The State Water Resources Control Board is currently funding $970 million in loans and grants for 12 projects that would provide about 62,000 acre-feet of recycled water per year for urban and agricultural irrigation and indirect potable use through groundwater recharge. An acre-foot is 326,000 gallons, enough for more than two households for a year.
California produced 728,000 acre feet of recycled water in 2020, up about 40% from 20 years ago. Santa Rosa’s 5 billion gallon production equals 15,344 acre-feet — enough to sustain 35,750 local households annually, or an average of more than 92,000 people.
Obstacles to tapping recycled water
Wastewater experts like to say all water on, in and above Earth is recycled and humans are using the same water as the dinosaurs.
But there are major constraints on how the modern system of sewage plants can respond, starting at Santa Rosa’s Laguna Treatment Plant, located about 2 miles southwest of the city limits.
It receives an average of 16.4 million gallons of wastewater a day from more than 225,000 residents and 6,500 businesses in Santa Rosa, Rohnert Park, Cotati, Sebastopol and parts of Sonoma County outside cities.
The water goes through a three-step, 15-hour treatment process that includes removal of solids, clarification and filtration through a 4-foot bed of granular coal. Finally, the water is disinfected with ultraviolet light, deactivating potentially disease-causing bacteria and viruses, used instead of chlorination.
Recycled water that receives tertiary treatment is deemed safe for irrigation of landscapes, pastures, playground and crops that are eaten raw.
The city says it recycles 98% of the wastewater flowing into the plant, and there’s obviously no desirable way to boost the flow. Successful conservation measures in recent decades have, in fact, reduced the total amount of water used by Californians — and the nation as a whole.