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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