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pH control is one method of stabilizing lead, orthophosphate is another (which Flint didn’t bother with). > Most important, the treated Flint River water lacke

pH control is one method of stabilizing lead, orthophosphate is another (which Flint didn’t bother with). > Most important, the treated Flint River water lacked one chemical that the treated Detroit water had: phosphate. “They essentially lost something that was protecting them against high lead concentrations,” Giammar says. Cities such as Detroit add orthophosphate to their water as part of their corrosion control plans because the compound encourages the formation of lead phosphates, which are largely insoluble and can add to the pipes’ passivation layer. … > The treated Flint River water had a relatively low pH that decreased over time. According to monthly operating reports from the Flint treatment plant, the city’s water had a pH of about 8 in December 2014, but then it slowly dropped to 7.3 by August 2015. Environmental engineers say that if water pH drifts too low in the absence of orthophosphate, the water can start to leach high levels of lead from pipes. > The pH drop over time seems to indicate that plant operators in Flint didn’t even have a target pH as part of a corrosion plan, Edwards says. Water utilities usually find a pH that’s optimal for preventing corrosion in their system. For example, in Boston, another city with old lead pipes, average water pH held steady around 9.6 https://cen.acs.org/articles/94/i7/Lead-Ended-Flints-Tap-Water.html https://cen.acs.org/articles/94/i7/Lead-Ended-Flints-Tap-Wat...

HPsquared 4y ago
pH is the fundamental thing, phosphate is the chemical patch that allows low pH water to be used. Basically they switched water source to something less alkaline than what they'd used previously - and didn't do anything to mitigate this. The phosphate is kind of a "patch" to the problem of low pH. Fruit juice and cola is of course much, much more acidic than the Flint water - orange juice for example is about pH 4 (that is, 1000 times more H+ ions than pH 7)

HPsquared 4y ago

pH is the fundamental thing, phosphate is the chemical patch that allows low pH water to be used. Basically they switched water source to something less alkaline than what they'd used previously - and didn't do anything to mitigate this. The phosphate is kind of a "patch" to the problem of low pH. Fruit juice and cola is of course much, much more acidic than the Flint water - orange juice for example is about pH 4 (that is, 1000 times more H+ ions than pH 7)