From Toilet to Tap

From Toilet to Tap

Facility uses sophisticated technology to transform wastewater into clean water.


3 - 12+


Engineering, Geography, Human Geography, Physical Geography, Physics, Social Studies, Economics

NGS Resource Carousel Loading Logo
Loading ...
Leveled by
Selected text level

Shivaji Deshmukh holds a plastic cup of water. He is a manager at Orange County Water District's Groundwater Replenishment System (GWRS).

Then, Deshmukh announces a fact about the water that might make some people's stomachs turn. "An hour and a half ago, this was treated sewage," he says. "A day ago, it was raw sewage."

In other words, it was likely in a toilet somewhere.

Deshmukh then chugs down the water without blinking — showing his complete faith in his project.

California often runs low on water, and the GWRS is trying to fight this with sewage from Southern California's Orange County. This gets transformed into water that is good enough to drink, according to government standards.

Before his big gulp, Deshmukh led me on a tour of the facility. He says the treated sewer water passes through three processes before becoming drinkable.

The Groundwater Replenishment System is just feet away from the Orange County Sanitation District (OCSD). This is where the sewage from northwest Orange County is first treated. Every day, OCSD sends water over to the GWRS through a .8 kilometer (.5 mile) long, 2.4 meter (96 inch) wide pipe.

Michael Gold is a former official for the Orange County Sanitation District. When water comes to the OCSD, "It's dirty," he says. "It's smelly. It's full of viruses and junk. As it comes out of our plant, it looks clean, but it's not clean enough to swim and bathe in."

Currently, OCSD sends about 378 million liters (100 million gallons) of treated sewer water over to the GWRS for recycling every day. Gold says that amount of water is roughly enough to fill up nearby Anaheim Stadium. That's where the Los Angeles Angels baseball team plays.

Three Processes

After OCSD sends treated water to the GWRS, it undergoes three processes to make it drinkable: microfiltration, reverse osmosis, and ultraviolet disinfection.

Microfiltration, the first step, gets rid of all solids in the liquid. It also gets rid of bacteria and protozoa, tiny lifeforms that can harm humans. Liquid is pushed through a series of fibers. These are filled with tiny, hollow tubes. Deshmukh compared it to drinking iced soda through a straw. The pollutants are like the ice, which are too large to be drawn up through the straw.

The water is propelled through the microfiltration fibers using giant, 600-horsepower engines. These are about twice as powerful as a Ford truck engine. After microfiltration, the water sits in a large holding tank.

Inside, the facility looks like a warehouse filled with stacks of plastic pipes.

Now, viruses, salts, and bits of medicines have to be filtered out. This is where a process called reverse osmosis comes in.

In reverse osmosis, conducted by OCSD, the water is pushed through plastic sheets by 1,000-horsepower engines. The plastic sheets separate the unwanted material from the water.

After this, we walked toward the final stage. We stopped at a series of steel tubes that are filled with ultraviolet (UV) light bulbs. This UV light destroys any of the water's remaining viruses.

After this, Deshmukh says, minerals are added back to the water.


Soon, Deshmukh and I tip back some plastic cups and drink a liquid that may have been swirling around a toilet bowl just a day ago. Still, this water actually has months to go before it will be sent through sinks and showers.

About 132 million liters (35 million gallons) of the water treated by GWRS is injected into Orange County's seawater barrier. The barrier is a series of wells that work like a dam.

Much of California's fresh water sits underground in deposits called aquifers. The barriers block salty seawater from coming into the underground freshwater supply.

About 246 million liters (65 million gallons) of the water is pumped 21 kilometers (13 miles) away to Anaheim, where it is released into several lakes. From there, it mixes with the region's rainwater and settles underground as groundwater. In approximately six months, chlorine is added to the groundwater, which further cleans out germs. Then, water is sent to taps in Orange County to be used by people and businesses.

As of 2015, the Orange County Water District treated 378 million liters (100 million gallons) of water daily. This would meet annual water needs of 850,000 people.

Another benefit is that the GWRS reduces the amount of treated wastewater released to the Pacific Ocean.

Sure, the idea of drinking reclaimed water might sound gross at first.

However, the success of Orange County's Groundwater Replenishment System changed California's thinking. There are now some proposals for similar facilities being built across the state.

Fast Fact

Water Wisdom
Before the Groundwater Replenishment System began processing treated sewer water in January 2008, the Orange County Water District's Water Factory 21 was the first facility to use reverse osmosis to make municipal sewer water into purified drinking water.

Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Stuart Thornton
Jeannie Evers, Emdash Editing, Emdash Editing
Kara West
National Geographic Society
Last Updated

October 19, 2023

For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource.


If a media asset is downloadable, a download button appears in the corner of the media viewer. If no button appears, you cannot download or save the media.


Text on this page is printable and can be used according to our Terms of Service.


Any interactives on this page can only be played while you are visiting our website. You cannot download interactives.

Related Resources