In summary
Suppliers now have detailed steps to create a new source of drinking water. But it’s not really “toilet-to-tap.” Due to the cost, it’ll likely be only large suppliers.
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In a milestone for creating a major new source of drinking water, California has approved its first standards for turning sewage into potable water supplies delivered to homes and businesses.
The State Water Resources Control Board, in a unanimous vote today, outlined for the first time how water suppliers can treat recycled water and send it directly to taps. Currently recycled water is mixed into aquifers or used for irrigation and other non-drinking purposes.
The new rules — which have been more than a decade in the making and were mandated by a state law — outline a slew of requirements aimed at ensuring that germs and chemicals are scrubbed from treated sewage.
Often dubbed “toilet-to-tap,” the process is actually much more extensive and complex, requiring multiple treatment steps overseen by 63 pages of detailed rules. The new rules also call for extensive monitoring to ensure the treatment is working.
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Preliminary Treatment: All the random debris in sewage is filtered out, typically using bars and grates. Essentially, the treatment process starts by removing the largest objects and moving on to the smallest.
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Primary Treatment: The waste then is sent to settling tanks, where heavy solids, such as fecal matter, sinks to the bottom and forms a sludge. Meanwhile, oils and soapy chemicals float to the top and form scum.
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Secondary Treatment: The next step is to remove organic matter and other biological contaminants from this clarified water. In aeration tanks, oxygen bubbles into the water, allowing microorganisms to gradually digest contaminants. After gorging, these microorganisms clump together and settle to the bottom of the tank.
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Tertiary Treatment: Wastewater that will be used for non-potable purposes, such as irrigating crops or golf courses, must then be disinfected. Typically, chlorine is used to kill bacteria, making the water safe for many purposes, but not for drinking.
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Advanced Purification: Additional steps are taken to purify the water enough to consume. It is disinfected with ozone, digested by microbes and filtered through activated carbon. Reverse osmosis clears away chemicals and salt, and finally, advanced oxidation with UV light cleanses remaining contaminants.
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Almost There: Then, finally, the wastewater will be subjected to the regular treatment that all drinking water currently undergoes.
Graphic by John Osborn D'Agostino
The sewage will be bubbled with ozone, chewed by bacteria, filtered through activated carbon, pushed at high pressures through reverse osmosis membranes multiple times, cleansed with an oxidizer like hydrogen peroxide and beamed with high-intensity UV light. Valuable minerals, such as calcium, that were filtered out will be restored. And then, finally, the wastewater will be subjected to the regular treatment that all drinking water currently undergoes.
California will be following Colorado, which already has regulations, and Texas, where the nation’s first direct potable reuse plant was built a decade ago. Rules are in development in Florida and Arizona, as well.
Nothing will go into effect immediately; the regulations must undergo a final review by the Office of Administrative Law before being implemented, likely next summer or fall. The first facilities are several years away.
“A city produces wastewater during a drought, and having that source available to augment other (drinking water) supplies can be critical,” said Darrin Polhemus, deputy director of the state water board’s Division of Drinking Water.
The water is expected to be more expensive than imported water, but also provide a more renewable and reliable supply for California as climate change continues.
The expense of the treatment and monitoring means that it will likely be limited to large urban water providers, Polhemus said.
“It will offer a resilient source in drought times for large water systems to be part of their portfolio. It’s not going to be a singular water source for some small community on the coast — that’s just not going to work out well the way these regs are written,” Polhemus said.
Fewer than a dozen people commented about the regulations at today’s meeting, all in support.
These regulations “really herald a new era for water reuse in California,” said Jennifer West, managing director of the trade association WateReuse California. “Communities across California will be able to benefit from this new, safe, resilient supply.”
Some environmental groups urged the board to adopt deadlines for more aggressive monitoring to reassure consumers about safety and ensure no outbreaks or other health scares derail the projects.
Board Chair E. Joaquin Esquivel directed the staff to report back within the next year to update the board on monitoring, contaminants and other issues.
A panel of independent experts determined that the regulations “adequately protect public health,” but reported that some requirements, such as for removing disease-causing germs, might be on the more conservative side, driving up costs.
This could “push utilities toward less environmentally desirable alternatives, such as extracting groundwater without replenishing it,” the panel said in a memo to the state board in September. It could also “limit the ability of smaller communities to use” the recycled water as drinking water.
“I don’t think anyone should be surprised that a water board regulator would choose to err on the side of public health,” said Kevin Hardy, executive director of the National Water Research Institute, a non-profit that coordinated the expert panel.
The Metropolitan Water District, the giant agency that imports water to Southern California, is already on its way to being among the first to directly use recycled water for drinking supplies with Pure Water Southern California, a multi-billion dollar project with the Los Angeles County Sanitation Districts.
By 2032, the plant is expected to produce about 115 million gallons of recycled water a day, enough for 385,000 Southern California households. Most will replenish groundwater, but some is expected to be added to drinking supplies upstream of Metropolitan’s treatment plant for imported water.
Mickey Chaudhuri, interim chief of operations at Metropolitan, applauded what he called a historic milestone.
“This marks a pivotal moment in California’s water management history,” he said at the public hearing today.
Last year, Gov. Gavin Newsom called for increasing recycled water use in California roughly 9% by 2030 and more than doubling it by 2040.
Most treated sewage — about 400 million gallons a day in Los Angeles County alone — is released into rivers, streams and the deep ocean.
Waste would undergo extensive treatment and testing before it’s piped directly to taps, providing a new, costly but renewable water supply. The state’s new draft rules are more than a decade in the making.
August 1, 2023
Unlike a year ago, water storage is above average. Whether the year is wet or dry, though, remains uncertain despite El Niño conditions.
November 17, 2023
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