Increased Lead in Water Associated with Iron Corrosion

When attempting to reduce lead solubility by lowering the finished water pH in Providence, RI, from similar to 10.3 to 9.7, consumer red water complaints and overall lead levels increased, prompting bench-scale tests and intensive field sampling into possible associations between higher particulate iron and particulate lead. At pH 10.3, iron release to water was as much as 35% lower in bench-scale tests and 99% lower in field samples compared with pH 9.7. Lower levels of particulate iron released at higher pH, translated to lower levels of particulate lead release after contacting downstream plumbing in bench testing. Although a significant decrease in distribution system iron at pH 10.3 did not immediately translate to decreased lead levels at all field sampling sites, complementary laboratory and field studies demonstrate that lead corrosion control is sometimes strongly linked to iron corrosion control.