PureBlue Blog


Toilet to Tap: Passing the Taste Test

January 22, 2019
Water Treatment

For basically ever, the idea of drinking recycled wastewater has been met with a very large gag response. Then, years of drought happened in California and water providers' thoughts turned to the age-old question, "Yeah, but how does it taste?" As it turns out, not so bad.

Researchers at the University of California, Riverside (UCR) recently published a study of wastewater that focused on its flavor rather than its safety, which already has been established. The idea of supplementing conventional groundwater with water that presently is being discarded by the millions of gallons holds great appeal, particularly during the extended drought conditions that the western U.S. is facing. According to a report in Eureka Alert, a service of the American Association for the Advancement of Science, Daniel Harmon, a graduate psychology student who was the study’s lead author, just the thought of recycled water provoked “disgust reactions,” with some people referring to the recycling process as “toilet to tap.”  

However, Harmon says, “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.” Hence, a taste test like none Pepsi could have imagined.

Most research on wastewater treatment has focused on its safety. The water is treated using reverse osmosis and then, through indirect potable use (IDR), it is reintroduced into the groundwater supply, where it merges with existing drinking water. Studies have found that IDR removes virtually all contaminants, and six California agencies employ IDR. However, the actual taste of the water had not been considered, at least not in a scientific study using a blind test.

The UCR study involved 143 people who were asked to taste IDR-treated water, conventional tap water and commercially bottled water and to compare their flavor. The water was presented in identical cups and were unlabled, so participants could not tell the water’s source. After tasting the water, they were asked to rank its taste from one to five, and to rank the samples according to texture, temperature, smell and color — all factors that influence people’s perception of taste.

The study included other factors that affect how individuals perceive flavor, including one test that gauged genetic differences in taste sensitivity using paper strips coated with phenylthiocarbomide (PTC). People who are highly sensitive to taste will find the strip to taste bitter. Researchers also weighed personality traits to determine participants’ water preferences. People who are “Open to Experience” are receptive to novel and diverse experiences. The traits of people who are anxious and insecure when facing new experiences were referred to as “Neuroticism.”

The people in the study who were more open to new experiences didn’t have a marked preference for any of the three different samples. The more anxious respondents preferred IDR and bottled water. And women were twice as likely to prefer bottled water as men. Overall the groundwater-based sample—tap water—was not as well-liked as IDR or bottled water.

The researchers suggest that favorable comparisons between reverse osmosis-treated water and bottled water may make consumers more likely to accept drinking recycled wastewater. They also suggest that any marketing to women should focus on these similarities and should cater to women’s “demonstrated openness to new experiences.”

Harmon said the researchers think the study will help them discover what factors people pay most attention to when they make decisions about water, and how to persuade them to give IDR a shot.

Apparently, it's only gross if you haven't tasted it.




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