Zapping Lead Pipes with Electricity Could Make Them Safer for Drinking Water
The toxic effects of lead—developmental delays, organ damage, even death—are well-known. But millions of Americans still rely on lead pipes to deliver drinking water. In an attempt to make them safer, researchers at the University of California, Berkeley, are working on a new technology that uses electrical current to rapidly build a protective layer on the insides of the pipes. In early tests they reduced the amount of the toxic metal entering water, but other scientists are skeptical of the method’s potential as a long-term solution.
Civil and environmental engineer Ashok Gadgil took on the project with his graduate student, Gabriel Lobo, after researchers found dangerous lead levels in the tap water for hundreds of homes in Flint, Mich. The crisis began shortly after the city started drawing water from the Flint River in 2014. That changed the water supply in two critical ways. “The first was that [the Flint River water] was more corrosive than the water they were getting from Detroit prior to the switch,” says Terese Olson, a civil and environmental engineer at the University of Michigan who is not part of Gadgil’s study. “The second problem is they didn’t add corrosion inhibitors, specifically phosphates, that were added to the Detroit water.”
These phosphates are often mixed with water in cities that still use lead service pipes, which connect buildings to a water main. Over several months the chemicals bind to dissolved lead and form a solid layer of lead phosphate crystal on the pipe walls. This coating, called “scale,” separates the water from the lead in the pipes themselves, and can prevent more of the metal from dissolving into the drinking supply.
Researchers think the corrosive Flint River water, without the protective influence of phosphates, may have eaten away the scale on local lead pipes—and that pieces of the broken-down scale, along with newly exposed lead metal, then polluted Flint’s drinking water. A 2016 study from the National Resource Defense Council indicates 17 million people around the United States now face a similar risk.
Protective scale can be rebuilt by adding phosphates to the water, but the buildup process can take months or years. Gadgil and Lobo, however, say they have found a way to do it in a matter of hours. Their method involves running electricity through a wire exposed to the phosphate-treated water within a pipe, and also through the pipe itself, giving the pipe a positive charge and the wire a negative one. This makes the pipe rapidly shed positively charged lead ions into the water, where they react with negatively charged phosphate ions to form lead-phosphate scale. As a result, scale accumulates on the pipe wall much more quickly than it would under normal circumstances.
Lobo says this approach causes a light but visible scale to form after about two hours. It looks like a paper-thin white lining on the inside walls of the test pipes, and is apparently enough to slash the amount of lead getting into the water. “It decreases the lead leaching rate by like 99 percent,” Lobo says. “But it won’t be enough to comply with the lead rule, if the pipe is bare to start.” Federal rules set acceptable lead levels in water at less than 15 parts per billion (though most scientists agree that no amount of lead is safe). After roughly eight hours, water inside Lobo’s treated test pipes had around 100 parts per billion.
Still, Lobo thinks he can improve the technology to lower lead levels further. “The other thing you need to consider is that actual lead pipes have pre-existing scale,” he notes. “It’s just small areas that become unprotected. The treatment will cover up those areas.” In a system like Flint’s—one that already has years of built-up scale, but recently suffered damage—Lobo’s technique might be able to bring lead back to safe levels. But first, it will require more testing. “The next part of the experiment is to try actual pipes in actual water systems,” Lobo says. He presented the research at this week’s American Chemical Society Spring 2019 National Meeting & Exposition.
Not everyone is convinced the technology holds a great deal of promise. “There are several issues I see with this,” Olson says. The biggest is that lead phosphate scale is not fully protective. “In most cases, lead particles are [still] getting into the water,” she says, adding that the only way to protect drinking water from lead contamination is replacing lead pipes, period. The new technique “is not a perfect fix at all. If you want the lead out, you’ve got to get the source out.”
Lobo agrees it is best to replace lead pipes—but says this is not always possible. “Replacing all of them is economically infeasible,” he says. “It costs something like $150 to $300 per meter of pipe, and some cities like Chicago have 80 percent of their water systems based on lead.” It will take time to replace lead pipes, and Lobo thinks the new technology might offer a temporary stopgap to reduce contamination.
But Olson remains unconvinced. Even if it is faster and cheaper than full pipe replacement, Gadgil and Lobo’s procedure still takes time and money, she points out. “Wouldn't a homeowner rather achieve immediate temporary protection with no fuss,” she asks, “by installing a tap water filter for 20 dollars?”