California considers adding treated wastewater to drinking supply through new proposal

• California regulators are set to vote on new rules allowing water agencies to recycle wastewater and reintroduce it into the drinking water supply.
• This initiative addresses California's persistent struggle to secure a reliable drinking water source for residents.
• The new rules would allow water agencies to directly treat and introduce recycled wastewater into the drinking water system, making California the second state after Colorado to permit this practice.

When a toilet is flushed in California, the water can end up in a lot of places — the ice in a skating rink, the manufactured snow on ski slopes, in pipes providing irrigation for farmland. And — coming soon — in your drinking glass.

California regulators on Tuesday are set to vote on new rules to let water agencies recycle wastewater and put it right back into the pipes that carry drinking water to homes, schools and businesses.

It's a big step for a state that has struggled for decades to have a reliable source of drinking water for its more than 39 million residents. And it signals a shift in public opinion on a subject that as recently as two decades ago prompted backlash that scuttled similar projects.

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Since then, California has been through multiple extreme droughts, including the most recent one that scientists say was the driest three-year period on record and left the state's reservoirs at dangerously low levels.

The Silicon Valley Advance Water Purification Center is pictured on Dec. 13, 2023, in San Jose, Calif. Treated wastewater is purified into drinking water at the facility. California regulators are preparing to vote on new rules for turning recycled wastewater into drinking water. (AP Photo/Terry Chea)

"Water is so precious in California. It is important that we use it more than once," said Jennifer West, managing director of WateReuse California, a group advocating for recycled water.

California has been using recycled wastewater for decades. The Ontario Reign minor league hockey team has used it to make ice for its rink in Southern California. Soda Springs Ski Resort near Lake Tahoe has used it to make snow. And farmers in the Central Valley, where much of the nation's vegetables, fruits and nuts are grown, use it to water their crops.

But it hasn't been used directly for drinking water. Orange County operates a large water purification system that recycles wastewater and then uses it to refill underground aquifers. The water mingles with the groundwater for months before being pumped up and used for drinking water again.

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California's new rules would let — but not require — water agencies to take wastewater, treat it, and then put it right back into the drinking water system. California would be just the second state to allow this, following Colorado.

The rules would require the wastewater be treated for all pathogens and viruses, even if the pathogens and viruses aren't in the wastewater. That's different from regular water treatment rules, which only require treatment for known pathogens, said Darrin Polhemus, deputy director of the division of drinking water for the California Water Resources Control Board.

In fact, the treatment is so stringent it removes all of the minerals that make fresh drinking water taste good — meaning they have to be added back at the end of the process.

"It's at the same drinking water quality, and probably better in many instances," Polhemus said.

It's expensive and time consuming to build these treatment facilities, so Polhemus said it will only be an option for bigger, well-funded cities — at least initially. That includes San Diego, where city officials have a plan to build a water recycling program that they say would account for nearly half of the city's water by 2035.

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Water agencies will need public support to complete these projects. The rules require water agencies to tell customers about the recycled water before they start doing it.

In San Jose, local officials have opened the Silicon Valley Advanced Water Purification Center for public tours "so that people can see that this is a very high tech process that ensures the water is super clean," said Kirsten Struve, assistant officer for the water supply division at the Santa Clara Valley Water District.

Right now, the agency uses the water for things like irrigating parks and playing fields. But they plan to use it for drinking water in the future.

"We live in California where the drought happens all the time. And with climate change, it will only get worse," Struve said. "And this is a drought resistant supply that we will need in the future to meet the demands of our communities."