The idea of drinking recycled water—that is, water that’s been taken from your toilet, mixed with other people’s toilet water and then cleaned up—naturally makes a lot of people very squeamish. Surprise fun fact for everyone currently insisting they would rather die than drink recycled sewage: Many of you are already drinking it!
Now you’ve finished scrubbing your tongue with industrial grade sandpaper, let’s find out how this happens. First off, not all recycled water goes back into our pipes. There are many different levels of what’s called “reclaimed water,” and they serve different purposes: Some is used in an industrial capacity, for example, while some is poured directly back into streams and rivers that have been affected by drought. A lot of it is used for irrigation, especially in the often-bone dry state of California, where parks and golf courses have been maintained with reclaimed water since 1929—thanks to the higher level of nutrients like nitrogen in this kind of water, it’s actually better for plants than the regular stuff.
And yes, of course, some of it becomes drinking water, although not always in the same way. Some communities direct the recycled water into their local groundwater basins (natural, underground water stores), while others add it to their surface reservoirs. In both cases, the idea is to dilute it with the existing water supply before it gets piped to the treatment plant and prepared for drinking. Ever the trailblazer in such matters, California is vying to become the first state to skip this step entirely, thanks to years of drought, and simply pipe the water straight from the recycling plant to the treatment plant, then on into their faucets.
The obvious thing to point out here is that whichever route the drinking water has taken, it’s perfectly safe to drink (as mentioned earlier, you may have been drinking it for years without knowing). According to the National Research Council, in fact, due to the sheer amount of effort that goes into cleaning it up, the risks from drinking reclaimed water may even be “orders of magnitude lower” than regular tap water.
Which brings us, finally, to the big question: How do they turn toilet water into drinking water? Here’s the process, step-by-step:
Step 1: The Chunks
When sewage first arrives at the plant, it passes through bar screens—literally, openings covered by thin bars—that stop things like sticks, rags and other larger items from getting through. After this, the water is bombarded with tiny bubbles, causing the smaller bits of grit to settle so they can be more easily separated.
Step 2: The Solids
The next stage is known as “primary clarification,” or in laymen’s terms, slowing down the water flow so that solids—yes, those solids—settle to the bottom. These solids are then removed and go on their own completely separate adventure: Known as “biosolids,” they are treated with anaerobic bacteria and de-watered (that is, completely dried out). At this point, they’re either used as fertilizer for agriculture or compost for trees and yards.
Step 3: The Bug Lunch
The next step for your old sewer water sees it getting pumped full of oxygen, whereupon hungry bacteria go into a feeding frenzy, disposing of much of the remaining organic material (that is, poop). Most of the remaining gunk gets added to the mess of biosolids from step three, although a tiny amount is used to reseed the next batch of water with the bacteria necessary to make this step work.
Step 4: The Final Scrub
After being filtered one last time to remove any fine particles remaining, the water is disinfected with chlorine for 20 minutes to kill undesirable bacteria. The chlorine is then removed with sulfur dioxide to make it safe for use before it’s released back into the wild, ready for the cycle to begin all over again.
So now you know the epic journey undertaken by your waste, all for the express purpose of getting back in your mouth. Cheers!