Can people distinguish the taste of tap, bottled and recycled water

If you are thirsty and someone hands you a glass of water, you might or might not ask where the water came from. If you trust the person, you probably don’t worry much about the health risks of drinking the water.

On the other hand, if you are told that the water comes from highly treated sewage effluent, you might think twice about taking a drink — even if you are assured that the water is cleaner than tap water, bottled water or any other source.

It’s a matter of perception, which is why some people drink only bottled water. They think it must be more pure than water from the faucet. But studies have shown that much of the bottled water on the market is just someone else’s tap water, and often the source is unidentified.

A recent study by researchers at the University of California, Riverside, conducted a taste test to see if people’s perceptions about drinking treated wastewater has any connection to the actual taste of water. Findings were reported in the journal “Appetite.”

The 143 participants were provided three samples of water in a blind taste test, meaning that there were no clues about the source of water. One was a brand-named bottled water, which had been purified through reverse osmosis; another was tap water from a groundwater source; and a third was tap water that came from an indirect reuse (IDR) source. IDR processing, which is used in at least six California water systems, involves treating the water to a high degree through reverse osmosis and putting it into the ground, where it mixes with existing groundwater. From there, it is pumped back out and treated as a normal groundwater source.

Many of the findings of the study were surprising to the researchers. For example, the IDR water and bottled water were preferred over the groundwater source by many of the tasters.

“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,” said co-author Mary Gauvain, professor of psychology at UC Riverside in a news release.

The groundwater source had the highest amount of sodium and carbonate, while the IDR source had more calcium. Concentrations of chloride and bicarbonate were similar for all three.

Another interesting finding: Women were twice as likely as men to prefer the bottled water.

Individuals who described themselves as more nervous or anxious than others had less preference for the IDR water, perhaps because of the higher mineral content. Individuals who described themselves as more open to new experiences showed a somewhat greater preference for the IDR water.

In describing the tastes, individuals often said their preferred choices had “no taste” or “no aftertaste,” which may be related to the mineral content. The IDR process may remove some unpalatable minerals during filtering, the authors said. Since IDR water goes into the ground, it may pick up other minerals that improve the taste.

The authors acknowledge that the preferences in the study may be more related to mineral content of each source than to the process that the water goes through before it gets into the drinking glass.

The taste of water involves many factors, starting with the makeup of a person’s own taste buds and saliva, as I described in a story last year in the Kitsap Sun:

“Experiments have shown that when a group of people with normal taste buds is given pure distilled water to drink, most people do not believe the water tastes normal,” I wrote. “Some even say it is slightly bitter or sour, perhaps because it contains less salt than saliva, or perhaps because it is totally lacking in minerals that people come to expect.”

As for mixing highly treated sewage effluent into the water supply, there are two hurdles to overcome. The first is convincing people that the water really is safe, such as by providing a clear assessment of the water content — including minute constituents that can make it through the treatment process, such as some pharmaceutical drugs.

Beyond an honest assessment of water quality, water managers need to address the emotional response of people when it comes to anything dealing with sewage. Revulsion is a deep-seated emotion designed to help people avoid contamination and disease.

One way to make treated effluent more palatable is to “naturalize” it by putting it into the environment, such as infiltrating it into the ground — even if that process makes it less pure before it goes through another step in purification. Removing or adding minerals may improve the taste.

Water itself — the H2O molecules — are no different in sewage than they are in bottled water or coffee. Water cycles through people, plants, clouds, soil, the ocean, and on and on. It gets used over and over again. The only real issue is the other chemicals that may go along for the ride.

Alex Spiegel of National Public Radio did a nice job analyzing the psychology behind the aversion people have to using treated wastewater and why people are more accepting of indirect use. Read or listen to “Why Cleaned Wastewater Stays Dirty In Our Minds.”

So far in Washington State, nobody is talking about using highly treated sewage effluent (“reclaimed water”) as a direct supply of drinking water — or even as an indirect supply where injection wells are close to extraction wells, as done in some areas of California.

Nevertheless, people’s concerns about the quality of their water may impair the acceptance of reclaimed water for irrigation, groundwater recharge, stream restoration or even industrial uses. Addressing both factual and emotional aspects of this issue should help get us over those hurdles.

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