U.S. Environmental Protection Agency
By Robert F. Service
ORLANDO, FLORIDA—An estimated 18 million Americans are at risk of lead leaching from old pipes in their homes and city water systems; such exposure can cause neurological problems in adults and—in children—delayed or stunted brain development. The impact of such leaching was on full display in 2015 in Flint, Michigan, when officials changed the source of city water to save money. The new water increased corrosion in the city’s lead pipes, releasing lead into the drinking water and exposing tens of thousands of children.
To prevent lead from leaching, many cities add negatively charged compounds called phosphates to their water source. When the phosphates encounter positively charged lead ions in the water, the two react to create lead phosphate, an insoluble minerallike crust that builds up on the inside of the pipe, sealing it and preventing additional lead ions from leaching into the water. But depositing that crust, a process known as scaling, can take years.
Now, researchers in California have found a way to speed this process 500-fold, by simply threading a wire down the inside of the pipe and temporarily switching on an electric current. The current actually causes more lead ions to leach into the water, but those ions then react with the phosphates to build up the mineral barrier. Once locked in place, the mineral scaling causes lead levels leaching into the pipe to drop by 99%, the researchers report today here at the semiannual meeting of the American Chemical Society. The process can create a scale in just hours, rather than months or years.
So far, the potential fix has only been tested in the lab. Later this year, the researchers plan to field test it at a school in Oakland, California, where normal scale buildup isn’t happening in the building’s lead pipes. If the new method works, it could offer cities around the world—including Flint—a fast and cheap way to seal lead in their aging pipes without having to dig them out of the ground.
Source: Science Mag