$\mathrm{Pb}$ in Tap Water Following Simulated Partial Lead Pipe Replacements

The concentrations of total, colloidal, and truly dissolved lead $\left(\mathrm{Pb}\right)$ were investigated in tap water following laboratory simulations of partial lead pipe replacements. Old lead pipes were recovered from service in New Orleans, La and mounted horizontally in an experimental apparatus at Tulane Univ. Municipal water was diverted for two weeks at low flowrates of $0.2$ or $1.1L/\min$ ($0.05$ or $0.3\mathrm{gal}/\min$) through two pipe trains operated continuously and two pipe trains operated intermittently. Samples were collected to determine relative concentrations and time needed for each form of $\mathrm{Pb}$ (total, colloidal, and truly dissolved) to stabilize below the U.S. Environmental Protection Agency action level (AL) of $15\mu g/L$ $\mathrm{Pb}$. Results demonstrate that total $\mathrm{Pb}$ concentrations exceeded the AL immediately following simulated partial pipe replacements. In most cases, total $\mathrm{Pb}$ concentrations were reduced below the AL by flushing for $15-30\min$ but subsequent sampling revealed total $\mathrm{Pb}$ concentrations greater than the AL. Continuous flow pattern flushing was more effective at stabilizing total $\mathrm{Pb}$ concentrations below the AL than intermittent flows. Results also demonstrate that colloidal $\mathrm{Pb}$ concentrations were $38-54\%$ of total $\mathrm{Pb}$ and truly dissolved $\mathrm{Pb}$ concentrations were $41-60\%$ of total $\mathrm{Pb}$ concentrations after stabilization.