Many areas of the United States--California in particular--are facing a water shortage, due in part to demands from a growing population living in traditionally arid places. Some believe that recycling wastewater, or treating sewage water to the point that it is safe to drink, may be the answer to a thirsty country's prayers.

The method makes water that is "abundant and safe," says Brent Haddad, PhD, associate professor of environmental studies at the University of California, Santa Cruz. "The technology is remarkable and can treat water to an often higher quality than the water that originally entered the system."

However, attempts to reintroduce purified wastewater into the aquifers and rivers from which cities draw their supplies has met vehement opposition from citizens' groups, stalling water recycling projects in cities from San Diego to Tampa, Fla. According to Haddad, who studies the success of water reuse initiatives, and University of Pennsylvania psychologist Paul Rozin, PhD, who studies disgust and contamination, this opposition comes more from a knee-jerk response to wastewater--the "yuck" factor--than from concerns about the water's chemical composition.

In people's minds it's "once in contact, always in contact," explains Rozin. "Even if you convince people you did every co nceivable thing to [purify] the water they would still be reluctant to drink it."

Yet Rozin notes there are ways to help people overcome the "yuck"--something he and other psychologists like the University of Oregon's Paul Slovic, PhD, a specialist in risk perception, have begun doing by consulting with Haddad and public water officials from such regions as California's Orange County and Elsinore Valley.

Together they are developing methods for making reclaimed water more palatable--such as designing systems that make the origins of such water less salient, "purifying" water in people's minds through association with environmental organizations and taking advantage of emotion's power over reason. And while this collaboration is in its infancy, some say that it may have contributed to one of the world's most successful reclaimed wastewater efforts--the Singapore NEWater facility.

The power of disgust

For most people, arguments typically made by water treatment officials about the chemical purity of reclaimed water hold no sway over a stomach-level sense that a substance is unclean, says Rozin. Factors besides the water's physical make-up, such as its history, lead people to feel that it has been contaminated, he says.

Research by Rozin and his colleagues in 1986 illustrates this point. In a study published in the Journal of Personality and Social Psychology (Vol. 50, No. 4), researchers placed a sterilized roach into a glass of water. All but one of the 50 participants refused to drink the water, despite being aware that the roach carried no diseases. Even after the researcher removed the roach from the glass, the thirsty participants would not drink the water. People consider human waste to be just as unclean as roaches, says Rozin. In fact, every culture social scientists have studied so far reviles excrement and everything it's associated with, he notes.

This disgust reaction applies even to things that appear similar to human waste products, he notes. In a study described in the book "Cultural Psychology" (Cambridge University Press, 1990), psychologists opened a sealed container of apple juice, poured it into a new bedpan and offered thirsty participants the opportunity to drink it. Most participants, including fans of apple juice, flatly refused. Even after avowing that they knew the bedpan had never been used, the participants still would not drink the juice.

Because these connections exist independently of scientific understanding, they cannot be combated with facts about the chemical makeup of a "contaminated" substance, such as wastewater, Rozin says.

Creating mental barriers

Instead, Rozin suggests tapping some of the processes that allow people to function in a world where almost everything, from currency to a co-worker's hands, has been in contact with something considered gross, such as a toilet seat. That is, humans create mental barriers to an object's history that allow them to ignore potential contamination.

One way for water officials to promote this useful blind-spot is by interjecting an extra step or two into the water-recycling process, perhaps by incorporating a short stretch of river in the water recycling plant, or by injecting treated water into an aquifer, some scientists suggest. A case in point: Residents of cities on the Rio Grande River in South America do not give much thought to the fact that a town directly upstream is discharging processed wastewater almost directly into their water intake, Haddad notes.

Using natural features "is more expensive than the normal system, but that extra expense might be necessary to get the public acceptance," he says.

Public officials can also counteract perceived contamination by linking reclaimed water with an environmental organization, Rozin says. The psychologist notes that a sweater formerly owned by a mass murderer may lose its stigma if it was handled by Mother Teresa. Reclaimed wastewater proponents can capitalize on this principle, suggests Rozin, by associating reclaimed wastewater with a group such as the Sierra Club through advertisements and endorsements--effectively neutralizing the liquid's perceived link to human waste, he notes.

Slovic has also shared his insights with wastewater recycling engineers, in part by speaking at a January conference on "Human reactions to water reuse" held in El Segundo, Calif. He suggests that people promoting reclaimed water emphasize its benefits. This tactic may seem obvious, but it operates through the human tendency to minimize risk when dealing with something considered to be positive, rather than to conduct a rational cost-benefit analysis, he says.

For example, says Slovic, someone who loves skydiving will tend to ignore the sport's obvious perils. And similarly, Californians who care about the environment and who appreciate that using reclaimed water can decrease pumping of natural aquifers will be prone to minimize the water's stigma.

Putting it into practice

In part by applying some of these psychologists' suggestions and directly consulting with Rozin, at least one reclaimed water project--Singapore's NEWater plant--largely avoided the public outrage that accompanied similar U.S. recycled-water efforts.

The water-reclamation facility, which supplies the island nation with 3 million gallons of drinking water daily, launched an award-winning public information campaign prior to its opening. By publicizing the importance of reclaimed water to the country's continued economic success, and also noting that a new water source could significantly decrease Singapore's dependence on nearby Malaysia's rivers, public officials put to work Slovic's principle of decreasing people's perception of risk by highlighting benefits.

A visitor's center, integrated into the plant, continues to underscore the benefits of reclaimed water, says Linda Macpherson, vice president of CH2M HILL, the company that designed the plant.

The Singapore facility also overcomes psychological barriers to reclaimed water by injecting the treated water into natural reservoirs, which, as previously noted, makes the water's origins less salient, says Haddad. And calling the water NEWater, as opposed to reclaimed wastewater, helps people frame out its origins, notes Rozin. Although, Macpherson adds, the name does accurately reflect the water's path through natural water sources.

Proponents of reclaimed water, with continued assistance from psychologists, hope to replicate Singapore's success in the United States, Haddad says.

"I think this collaboration has already started a rethinking of how this industry interacts with the public," says Haddad. "They are learning to address [the public's] affective concerns and their concerns with contamination--which could go a long way toward promoting this technology."

Further Reading

  • Finucane, M.L., Alhakami, A., Slovic, P., & Johnson, S.M. (2000). The affect heuristic in judgments of risks and benefits. Journal of Behavioral Decision Making, 13(1), 1-17.

  • Haddad, B. (2000). Rivers of gold: Designing markets to allocate water in California. Washington, DC: Island Press.

  • Rozin, P., & Nemeroff, C. (1990). The laws of sympathetic magic. In J. Stigler, R. Shweder & G. Herdt (Eds.), Cultural psychology. (pp. 205-232). Cambridge: Cambridge University Press.

  • Slovic, P., Finucane, M., Peters, E., & MacGregor, D.G. (2000). The affect heuristic. In T. Gilovich, D. Griffin & D. Kahneman (Eds.), Intuitive judgment: Heuristics and biases. (pp. 397-420). Cambridge: Cambridge University Press.