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I counted seven different brands of bottled water at my local 7-Eleven, with none of them carrying the label “Toilet to Tap.” While most might pass on such a brand name, a new blind taste test shows that people actually ranked toilet to tap water comparable to bottled water and even preferred it over tap water.
Researchers at the University of California, Riverside and Santa Barbara City College asked 143 undergraduate students to judge conventionally treated, groundwater-based tap water, bottled water that had gone through reverse osmosis and “indirect potable reuse” (IPR) water.
At the very least, toilet to tap does have a catchy ring. IPR water refers to treated wastewater that’s intended to be put back into groundwater supplies. In the big picture of the water cycle, that water will eventually make its way back to our drinking water. But as the name implies, IPR water does not go directly into any water source meant to be used for drinking water.
Studies have found the purification process of making IPR water removes virtually all contaminants. Still, that doesn’t mean many people will gladly drink a glass of it.
Determining how to convince those disgusted by the mere thought, let alone the actual reality, of drinking … er, toilet water could be key to maintaining adequate water supplies into the 21st century.
Spurred by drought and growing populations, many cities are already incorporating recycled wastewater into their water supplies. We’ve read some studies that say an average city that recycles all its wastewater could reduce how much “fresh” water it needs by 60 percent.
Toilet to tap gained strength in the wake of the recent California drought. As initial water restrictions took hold, a lot of ideas that were long dismissed as too controversial, expensive, unpleasant, or all three, started getting another look.
Efforts in the 1990s to recycle wastewater in San Diego and Los Angeles were beaten back by activists, who coined the derisive term toilet to tap. Los Angeles even built a $55 million purification plant during a time, but never used it to produce recycled water. Instead, the water went to irrigation.
But now, six California water agencies employ IPR to replenish their drinking water sources. These include the Water Replenishment District of Southern California, the Orange County Water District, the Los Angeles County Department of Public Works, the Inland Empire Utilities District, the city of Los Angeles, and the city of Oxnard.
Toilet to tap, however, does present most of us with a strong “yuck” factor. Even one of the editors at PHCPPros HQ scrunched up her face at the thought. People tend to judge risk emotionally, and a phrase like toilet to tap can undercut earnest explanations. But other research on the matter has shown that highlighting the benefits of recycled water – and the need – can shift emotions to a more positive reaction and help diminish the sense of risk.
The inevitable squeamishness over drinking water that was once waste ignores the fundamental fact that water is water. Recycling water is becoming a necessity for a sustainable water future. It’s a cheaper and guaranteed resource, and it’s all around us.
There’s a lot more to toilet to tap water than toilet water. Think of all the water that goes down the drain every time you rinse an apple or hose off your car. That water is an untapped resource.
Plus, the use of recycled water is hardly untried and untested.
It’s already commonplace for irrigation with purple pipe signifying the delivery of secondhand water to golf courses and farms. While we aren’t exactly talking about it, “grey water” while certainly not meant to drink is perfect for watering backyard plants and gardens.
Call it what you want, wastewater that’s meant to eventually be drinking water again is just as safe as anything else you drink once it undergoes a rigorous filtering process done at specialized purification facilities.
The wastewater is stripped down to the H, 2 and O. Most reclamation plants include the first step of microfiltration that strains out anything larger than 0.2 microns, removing almost all suspended solids, bacteria and protozoa.
After that comes reverse osmosis, a gold standard in purification, that removes other impurities, including viruses, pharmaceuticals and dissolved minerals. Last but not least, a zap of ultraviolet light and a bit of hydrogen peroxide disinfects further and neutralize other small chemical compounds.
While studies have found IPR removes virtually all contaminants, no one has considered its relative taste in a blind taste test or in a scientific study.
The researchers from the California colleges hoped that by showing that IPR water tastes the same as other common sources of drinking water, they could make the notion of recycled water more appealing.
After tasting the three different types of water in unlabeled cups, participants were asked to rank the samples on a scale of one to five for taste, and also to rank them in categories like texture, smell and color.
The research team also assessed factors that might influence taste perception, including genetic differences in taste sensitivity using a measure of sensitivity to paper strips coated with the chemical phenylthiocarbomide (PTC). PTC either tastes bitter or tasteless depending on the taster. Those who found the strip’s taste to be bitter were considered to be more sensitive to taste.
The students also took a quick personality survey from which they were grouped on a scale ranging on their openness or nervousness to try new things.
Prior to conducting the test, researchers hypothesized the three waters would earn equal scores. In fact, one emerged the least preferred and was one of the study’s biggest surprises.
“The groundwater-based water was not as well liked as IPR or bottled water,” said Mary Gauvain, a professor of psychology at UC Riverside and co-author of the study. “We think that happened because IPR and bottled water go through remarkably similar treatment processes, so they have low levels of the types of tastes people tend to dislike.”
Sensitivity to PTC had no effect on the results. Perhaps not surprisingly, participants more open to new experiences liked the three samples about the same with no clear preference. However, those scoring higher on the personality scale for nervousness expressed a preference for IPR and bottled water, and were more negative about the taste of tap water.
Not every study participant was a fan of recycled wastewater, though. Women were twice as likely to prefer bottled water when compared to men. The researchers theorize that women register higher “disgust reactions” than men, which means their reactions to tastes they dislike is that much more extreme.
Still, the study's results are promising – although the challenge of getting people on board with recycled wastewater remains.
"It seems that this term (wastewater), and the idea of recycled water in general, evokes disgust reactions," lead author Daniel Harmon said in the press release. "It is important to make recycled water less scary to people who are concerned about it, as it is an important source of water now and in the future."
These reactions, both men’s and women’s, are the subject of the team’s next research.
In their conclusion, the researchers suggest that favorable comparisons between reverse osmosis and bottled water may make consumers more amenable to drinking recycled wastewater.
“We think this research will help us find out what factors people pay attention to in their water decisions, and what populations need to be persuaded to drink IPR water and how to persuade them,” Harmon said. l
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