Why recycled Arizona wastewater to use as drinking water is safe

Arizona cities are on the hunt for new sources of drinking water and recycling the water that goes down your drains is part of the solution.

The Colorado River provides a significant portion of Phoenix's drinking water supply currently, but it's shrinking from climate change and overuse. Phoenix is turning to advanced water purification to mitigate the dwindling river supply, sometimes called "toilet to tap" by critics.

The technology essentially takes all the water that goes down your household drains, cleans it, and then sends it back to you. The idea that your toilet water could end up as drinking water grosses people out, but the reality is, we already drink purified wastewater. It's called indirect reuse.

Here's what you need to know about how it works.

The water that goes down your toilet, shower or sink becomes wastewater, or effluent. Right now, it travels from your drains to a wastewater treatment plant where it's cleaned and then sent elsewhere for non-potable purposes, meaning it isn't drinkable. Some cities send a portion of the treated water underground, where it goes through a natural filtration system and is then later extracted, or pumped out, for drinking purposes. That's called indirect reuse.

For subscribers:Exclusive: Phoenix plans to make wastewater drinkable on mass scale by 2030

Direct reuse skips the part where you inject water into the ground. Instead, the effluent goes to the wastewater treatment plant where it goes through a rigorous purifying process. Phoenix water officials say it's quicker and more efficient than indirect reuse.

There are multiple ways to go about direct potable reuse, Phoenix Water Resources Director Troy Hayes told The Arizona Republic. For Phoenix, the plan to is to clean the wastewater via:

Hayes said the water is monitored by sensors throughout the process and is tested at the end to ensure it complies with the state's quality standards for drinking water. If the purified water didn't meet quality standards, it would be discharged to the Salt River, Hayes said.

Advanced water purification will mean Phoenix can reuse about 40% of the water that gets sent to households in the first place — that's the amount most households send back down the drains.

It's not a silver bullet. Homes will always need an initial freshwater source. Residents can't survive on recycled wastewater because every time the water goes through the process, some is lost to outdoor use. Phoenix's water planning documents show about 60% of a household's water consumption is lost to outdoor use, which is why the city is focused mostly on encouraging outdoor water conservation, Phoenix's water advisor Cynthia Campbell says.

But recycling wastewater provides cities with a new source of drinking water they didn't have before. This is critical because cities' current supplies depend heavily on the Colorado River, which is shrinking. Plus, Arizona shares the river with other states and it's highly likely the allocation agreement, which expires in 2026, will provide less water to us in the future.

Reporter Taylor Seely covers Phoenix City Hall for The Arizona Republic. Reach out to her at [email protected] or on Twitter @taylorseely95.