Is California Recycling Sewage Water for Drinking? Here’s What You Need to Know

California regulators approved standards for turning sewage water into potable drinking water for residents and businesses. Here’s what you need to know.

Updated: December 21, 2023
Jeremiah Zac


California, the economic and agricultural powerhouse of a state, has always had one major weakness: water. 

The precious resource the state so critically depends on is unevenly abundant in less populated areas and scarce in metropolitan Southern California, often requiring access to faraway sources such as the Colorado River and Owens Valley.

While drought has always been an issue to wrestle with, the state has historically implemented a variety of major projects to transport and treat water for the state’s 40 million residents.

One project, in particular, has gained notable attention.

On December 19, 2023, the State Water Resources Control Board unanimously approved strict rules that will allow cities to transport purified wastewater into drinking water supplies, also known as direct potable reuse. California will be behind Colorado, which already has direct potable reuse regulations in place, and Texas, which built the nation’s first direct potable reuse plant in 2013.

The first stage of the project is expected to be completed by 2032 and will provide 150 million gallons of recycled water a day for 400,000 households in Southern California.

While the idea of turning sewage water into drinking water may—quite understandably—be an objectionable topic, many may be surprised to learn that many clean water sources in California and other US states have already had an indirect relationship with recycled sewage water for several decades. 

For about 60 years now, wastewater recycling plants in California undergo a stringent process of treating sewage water, converting it back to conditions close to how it exists in lakes and groundwater, and then reusing it for non-potable purposes such as irrigating landscapes, crops, and golf courses.

Some recycled water is distributed back into clean water sources such as rivers, lakes, and aquifers, where it will eventually reach a potable water treatment plant and be used for drinking.

The difference between this process and the one approved on Dec 19th is that recycled sewage water can now be distributed directly into drinking water piping systems; hence the term 'direct potable reuse.’

How does direct potable reuse work?

While the process for recycling wastewater for non-potable uses is stringent enough, the process for direct potable reuse is even more comprehensive. 

And rightfully so.

Wastewater, whether that of dense urban areas or agricultural origin, is appropriately polluted, brimming with bacteria, parasites, viruses, insecticides, pharmaceuticals, and industrial chemicals, all of which can make anyone deathly ill.

Therefore, an extensive series of steps will be applied to remove specific contaminants at separate stages, resulting in water that is now suitable to be taken through the normal purification process for drinking.

Direct potable reuse diagram - John Osborn D'Agostino - CalMatters

  1. Preliminary Treatment: First, all large debris is filtered out with bars and grates.

  2. Primary Treatment: The waste is sent to tanks, where heavy solids settle to the bottom and form sludge, while oils and soapy chemicals float to the top and form scum.

  3. Secondary Treatment: Oxygen bubbles are injected into aeration tanks, allowing microorganisms to digest contaminants. These microorganisms then clump together and settle to the bottom of the tank.

  4. Tertiary Treatment: Wastewater that will be used for non-potable purposes, such as irrigating crops or golf courses, must then be disinfected with chlorine.

  5. 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 the remaining contaminants.

  6. Almost There: Then, finally, the wastewater will be subjected to the regular treatment that all drinking water currently undergoes.

Rachel Becker of CalMatters writes, “It is 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 are restored. And then, finally, the wastewater is subjected to the regular treatment that all drinking water currently undergoes.”

Because of the high concentration of contaminants in wastewater, particular measures will be applied to break down certain substances, such as anti-depressants and pain relievers, which can often be found in recycled wastewater. Due to the stringent attention to detail, some argue that water treated for direct potable reuse is actually cleaner than surface water before it reaches regular drinking water treatment.

How do drinking water treatment facilities work?

Once the wastewater has undergone the initial cleaning process, removing large particles and reducing the concentration of contaminants, it can then be taken to a treatment facility to be purified for drinking.

Public water treatment facilities can use a variety of treatment methods for drinking water, but most follow an overall general process involving the following methods.

The processes of sedimentation, coagulation, and flocculation are responsible for removing larger suspended particles, while activated carbon filtration removes specific chemical contaminants. Disinfection through chlorination or UV radiation eliminates harmful pathogens such as bacteria and viruses. Finally, some treatment facilities have a remineralization process where beneficial minerals such as calcium and magnesium are added back into the water before being distributed to the public.

All public treatment facilities are regulated by the EPA and must adhere to certain quality standards under the Safe Drinking Water Act, which lists 90 known contaminants that are found in water. Each of these contaminants has a maximum concentration level that must be met before being distributed in order for the governing agency to be considered compliant under federal law.

At this point of the treatment process, whether it started as recycled wastewater or came from a lake, the water adheres to the same treatment standards and must produce the same results before being distributed to the public.

So, is recycled sewage water safe to drink?

It depends on how comfortable you are with drinking tap water.

Let's put it into perspective.

The total volume of water on Earth never changes—it can change composition and location, become contaminated and purified, but not a drop of H20 can be added to or subtracted from the total amount circulating throughout the planet.

Through the Earth’s hydrologic cycle, water continuously evaporates from surface water sources into the atmosphere and precipitates back down as snow and rain to replenish rivers, lakes, and underground aquifers. During the cycle, water undergoes many chemical and compositional changes, moving between a solid, liquid, and gas, collecting a variety of contaminants as it travels through various regions, and purifying once again as it evaporates back into the air.

The problem that pollution poses is that it decreases the availability of clean, drinkable water that societies need to thrive. In the case of California, drought occurs when the clean water sources from the ground or from rivers become depleted due to overuse, and thus, new means of accessing and purifying water need to be explored.

No matter how contaminated a source of water may be, the H20 molecules are always present and can always be isolated through natural or artificial processes. Direct potable reuse plants are attempting to separate the H20 molecules from a stew of contaminants through a series of purification stages. 

Should I continue purifying my water at home?

The question then is, if the end result is the same regardless of where the water came from, just how clean is it by the time it flows out of the tap?

Federal laws like the Safe Drinking Water Act of 1974 are meant to set standards for local agencies to adhere to, expecting safe water conditions for all residents. This means that US drinking water quality is much higher than in regions where no standards are set.

However, even the SDWA's Primary Drinking Water Standards permit some trace levels of certain contaminants to pass through. The truth is that it is very difficult to achieve a 0% contamination level in public drinking water supplies due to the high volume of water being processed, the number of people being served, and the cost of resources required to treat such a high concentration of contamination.

This is why it is always a best practice for households, whether relying on city water or a private well, to test and purify water themselves. Home filtration systems are the only way to guarantee clean water for consumption, adding an extra level of protection and peace of mind even after the public treatment processes have been applied.

Home reverse osmosis systems are an excellent means of isolating all contaminants from water sources, ensuring only the H20 molecules, along with beneficial minerals, are being consumed.

Home water distillers replicate the hydrologic cycle on a small scale and are one of the most effective means of purifying water.

Gravity filters such as the Berkey are popular and convenient ways of having great-tasting, safe water at home.

It is also wise to test your tap water with a home testing kit or laboratory service to find out exactly what kind of purification system best suits your water conditions.

The bottom line is that whether the public water source is from a regular drinking water treatment facility or from a direct potable reuse plant, the quality of the water coming through the tap should still meet the SDWA standards, but testing and purifying the water yourself is still the only way to guarantee your own standard of purity.

Thank you for taking the time to read our article about recycling sewage water in California. We'd love to hear your feedback in the comments section below. If you've found this article to be useful and are interested in learning more, be sure to sign up for our newsletter.

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I'm Jeremiah, the owner of World Water Reserve. I'm a writer and researcher with a particular interest in sustainability and rural living, water scarcity, and innovative water purification methods. I utilize my multimedia and communication experience in the NGO and humanitarian fields to bring light to important topics. My passion is to educate others on the reality of the global water crisis and on ways to sustain themselves and their families in the midst of it.
Jeremiah Zac