'Toilet to Tap' Water Surprisingly Good, Study Finds

Apr 16, 2018

Scientists have long known treated wastewater is safe to drink but how does it taste when compared to "conventional" groundwater and bottled water?

Researchers at the University of California, Riverside (UCR) asked 143 people to compare the two in a blind taste test.

This is especially important in California where residents have dealt with years of drought. Recycled wastewater has gained traction even though some refer to the technology as "toilet to tap."

Wastewater is treated using reverse osmosis and is commonly reintroduced into groundwater supplies, where it re-enters the drinking water system. It's called indirect potable reuse, or IDR. Studies have shown IDR removed virtually all the contaminants.

“The groundwater-based water was not as well liked as IDR or bottled water,” said Mary Gauvain, a professor of psychology at UC Riverside and co-author of the study. “We think that happened because IDR and bottled water go through remarkably similar treatment processes, so they have low levels of the types of tastes people tend to dislike.”

“It seems that this term (wastewater), and the idea of recycled water in general, evokes disgust reactions,” said Daniel Harmon, a graduate student in psychology and the lead author in the study on water taste. The study published in print in the February edition of the journal Appetite.

However, Harmon added: “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.”

The Test

The waters were in unlabeled similar cups. After participants tasted them they ranked the samples' taste from one to five in the categories of texture, temperature, smell, and color.

Researchers suggest this study may lead to more people being amenable to drinking recycled wastewater and they suggest marking to women who make most consumer purchasing decisions.

“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 IDR water and how to persuade them,” Harmon said.

One surprise for Gauvain and Harmon is women preferred bottled water two-to-one over men.