The inside of a Flint lead service line. Image credit: Terese Olson/University of Michigan College of Engineering
A recent study of the lead service lines in Flint’s drinking water system has shown what looks like a Swiss cheese pattern in the interior crust of the pipes, with holes where the lead initially was.
Titled Forensic Estimates of Lead Release from Lead Service Lines during the Water Crisis in Flint, Michigan, the team of researchers included six undergraduate students, four graduate students, two post doctorate students, and six faculty members from the University of Michigan’s Flint and Ann Arbor campuses.
The research study, led by research scientists at the University of Michigan College of Engineering, backs the generally accepted view that the lead in the pipes contaminated the systems because the water distributed in Flint has not been treated to prevent the corrosion of the pipes. However, this is the first piece of direct evidence connected to the water crisis, as previous studies and reports had simply pointed to it, and contradicts a claim a regulator made earlier in the year that chemicals for corrosion control would not have staved off the crisis.
But now, the research findings simply highlight how vital uninterrupted anti-corrosion treatment is, especially for the aging water systems that serve millions of homes around the world.
The team, through study of the rust layer of the pipes, as well as its chemical composition, found that the average lead service line in Flint released some 18 grams of lead throughout the 17 months they carried the untreated waters from the Flint River through the system.
“This is the amount of lead that would have entered a single home,” Terese Olson, a University of Michigan associate professor of civil and environmental engineering, said. “If we average that release over the entire period the city received Flint River water, it would suggest that on average, the lead concentration would be at least twice the EPA action level of 15 parts per billion.”
Additionally, the lead is not just in the pipes.
“Some was consumed,” Olson said. “Some washed down the drain. Some might still be stored in the home’s plumbing. In other words, there is a chance that some of that lead is a potential health risk even after the lead service line is removed.”
For instance, if a lead service line is connected to a home through galvanised steel pipes, the steel pipes can act as a sponge for the lead, holding them before later releasing participles that hold the poisonous metal, study co-author Brian Ellis, an assistant professor of civil and environmental engineering at the University of Michigan.
Electron images of a cross-section of rust inside pipe samples taken from Flint’s lead service lines. The holes in what is known as the “Swiss cheese pattern” are where the lead in the pipes used to be, according to researchers. Image credit: Brian Ellis/University of Michigan College of Engineering
Additionally, the research scientists crushed the pipe linings to study what they were made of. In the pipes from Flint, they found a greater ratio of aluminium and magnesium to lead as compared to other lead service lines when contrasted with data collected from 26 other water utilities.
“We estimated how much lead was ‘missing’ in order to bring the Flint lead scale into line with the amount of aluminium and magnesium that was reported in other communities,” Olson added. “That missing lead represents what was leached from the pipes during the Flint corrosion episode.”
As lead pipes age, the atoms found on their surface will rust, reacting with oxygen as well as other chemicals in the system. While water treatment cannot prevent that process, it can keep the rust layer from breaking down.
“It’s like when you put an old penny in a glass of Coca-Cola and watch it get shiny again,” Ellis explained. “The acid in the Coca-Cola dissolves the copper corrosion product. This is similar to what happened in Flint’s lines. You can have a stable corrosion product, but when you change the water chemistry, the oxidised lead compounds on the surface may become unstable and readily dissolve.”
Water utilities who have both corrosive water and lead service pipes in their networks add orthophosphates to prevent the rust from breaking down. But when Flint moved their water source from Lake Huron to the more corrosive water from the Flint River in order to cut down on costs, the utility did not adjust their treatment by adding the aforementioned orthophosphates.
“Beyond implications for Flint, we demonstrated that small changes in water chemistry can release what was stable lead in a fairly quick pulse,” Ellis continued. “This is a known condition. So while we weren’t surprised, being able to show it underscores the importance of maintaining uninterrupted lead control.”
Source: University of Michigan