As the world's population grows and the climate continues to change, many locales are facing severe shortages of drinking water. And while the technology exists to turn sewage into drinkable water, the trick is convincing people to swallow the stuff.

Psychologist Carol J. Nemeroff, PhD, discussed this problem in a presentation entitled "Public Acceptability of Recycled Water: Getting the Cognitive Sewage Out After the Physical Sewage Is Gone" at the 2011 Annual APA Convention. Nemeroff, an expert in so-called magical thinking and contagion research, talked about the challenge of moving people beyond the image they have of "toilet to tap." She described a technology called tertiary recycling, a three-level system that starts with sewage and ends with "really excellent, good quality water."

It's great stuff, she said, but people don't want to drink it. A tertiary recycling system is in place in Los Angeles, for example, but the water is used primarily for irrigation. "Currently, nobody drinks it," she said.

The problem is what's been termed the magical law of contagion, she said, which essentially says once something has come in contact with something disgusting, it's always in contact in people's minds.

She described a five-city survey she conducted to gain better understanding of the level of purification that would move people toward drinking recycled water. When respondents were asked whether they were willing to drink recycled water (it was defined in the question), 38 percent said they were willing, 49 percent were uncertain and 13 percent said no.

"We need to break the perceived connection between water and its history of sewage," she said.

—K. Mills