Your toilet is probably the very last place you would look for fresh drinking water. But, as it turns out, water that was once in a toilet may already be coming out of your tap — and not by accident. When we saw the recent Scientific American article “Drinking from the Toilet,” which describes the phenomenon of purified wastewater, we had to dig deeper. We wanted to know: What's the advantage of reintroducing water from the sewer back into our drinking supply? And, is it really safe?
The U.N. has announced that by 2030, the world’s demand for water will exceed its supply by 40%, leaving almost half the world’s people with inadequate water access. Population growth, urbanization, and climate change are all accelerating the process. Certain areas of the U.S. have been especially hard-hit by water shortages, including California and Texas — both of which are now getting serious about reintroducing sewage water into their drinking supplies. Not all sewage water was once in a toilet; most of it comes from sinks, washing machines, dishwashers, and bathtubs. But, according to pro-wastewater municipal officials, by the time the water is treated, it doesn’t matter where it came from.
Drought-stricken Wichita Falls, TX is a poster child for recycled wastewater. In November of 2013, the city completed its Direct Potable Reuse (DPR) project: a 13-mile-long pipeline that will introduce five million gallons of treated and tested wastewater into the city’s potable water supply each day. The project is now in the final testing stages and is prepping for rollout. Until then, Wichita Falls’ wastewater is treated and dumped into a local river that carries it to a reservoir, where natural solar radiation continues the purification process. Then, other cities treat the water again for their own use. So, what DPR will do is speed up the recycling process that's already in place, by connecting the city's water treatment plant with its wastewater treatment plant.
Some detractors refer to purified wastewater as “toilet-to-tap” — but it’s more complicated than that. Water is generally treated post-use anyway, whether it goes on to water a golf course or reenter the drinking supply. Wichita Falls treatment plant operators tested the town’s treated wastewater and found that it already met 94 of the 97 standards that qualify water as potable. To hit the remaining three standards, the water needed to travel to a regular treatment plant to be stripped of 1) trihalomethanes, 2) nitrates, and 3) microbes, which are produced when disinfectant products such as chlorine and nitrogen peroxide interact with water. Disinfectant treatments aren't dangerous in and of themselves, but what is harmful is their carcinogenic byproducts: Trihalomethanes and microbes are known to cause cancer, while nitrates can go on to produce carcinogens. Plants such as the one in Wichita Falls tackle this problem with a powerful one-two-three punch of microfiltration, reverse osmosis (forced passage through a permeable membrane), and ultraviolet light exposure.
The biggest remaining challenge for the recycled wastewater movement is to overcome public perception — in other words, the “ick” factor. If your first instinct when you read the beginning of this story was to switch to bottled water, you’re not alone. But, no evidence indicates that treated sewage water is less safe or less healthy than any other kind of potable water. We have a long way to go, though, before it becomes a significant source: In 2010, only one tenth of a percent of the nation's municipal wastewater was reintroduced into potable water supplies. While we’re not yet recommending you drink directly from the toilet like this guy, toilet water could soon become as acceptable to us as it is to our pups.