LEAD LEACHED FROM HOUSEHOLD PLUMBING AND THE EFFECT OF WATER PH LEVELS

The recent crisis in Flint, MI, has raised awareness of the hazards of lead (Pb) in public water supplies. Pb has long been known to be hazardous to humans, and consumption of Pb, particularly by children, can result in irreversible damage to the nervous system. The U.S. EPA banned the use of Pb in public water systems (1986), yet many cities have aging infrastructures with Pb pipes. Moreover, many older, privately-owned buildings still retain old Pb pipes. The purpose of this research is to gain a better understanding of the rates of Pb leaching from pipes in water of different temperatures and pH. Previous studies have shown that as the pH of water and the stagnation time increases, the concentration of dissolved Pb also increases, yet few controlled experiments that simulate actual conditions have been carried out.. This project’s controlled lab experiment consisted of Pb pipe sections immersed in water of different pH for 6 weeks. Of the 8 experiments, 4 were heated to constant temperatures of 41°C-43°C, while the other 4 were left at room temperature (25°C). Water samples were taken at one- to two-week intervals and analyzed by XRF spectroscopy. The highest Pb concentration was 518 ppm, well in excess of the EPA limit of 0.015 ppm (15μg/L). Room temperature experiments produced Pb concentrations up to 167 ppm, while heated experiments generally resulted in higher concentrations. As expected, Pb concentrations in water were inversely proportional to pH. Although previous research has shown that as the stagnation time increases, the concentration of Pb increases, the results of these experiments were not as definitive. Of the 8 experiments, only 3 showed a consistent increase in Pb concentrations over time, suggesting that some Pb may have actually precipitated out of solution, although there was no obvious evidence of this process. This study indicates a need for more thorough laboratory experiments in order to develop a better understanding of the rates Pb dissolution under different temperature and pH conditions.