You are here:
KNOWING CHEMISTRY CAN HELP GET THE LEAD OUT
Citation:
BURLINGAME, G. A., M. R. SCHOCK, AND M. A. EDWARDS. KNOWING CHEMISTRY CAN HELP GET THE LEAD OUT. OPFLOW. American Water Works Association, Denver, CO, 32(9):24-26, (2006).
Description:
Lead in tap water comes from the materials used in plumbing such as from leaded solder, lead pipe, and lead-containing brass found in fittings and faucets. Fortunately, the surface of brass eventually becomes passivated when in contact with most waters. Oxidants in water (usually oxygen, chlorine, chloramine) react with lead-containing materials to convert lead from its metallic, solid form (Pb0) into the oxidized and soluble Pb(II) form of the metal. Lead forms passivating films with carbonates, phosphates and sulfates. A water system with a free chlorine residual that is persistent could end up with a predominantly PbO2 scale covering the surface of the pipe scale which reverts back to the more soluble phases (such as PbO) when the strong oxidant is removed or reduced. Natural organic matter (NOM) in water plays a role in the corrosion and occurrence of lead. The effects of NOM in the water on the soluble/particulate lead are significant. In relation to lead leaching, worrisome galvanic corrosion can result when a copper pipe is directly connected to a lead-bearing material (e.g., pipe, solder, brass). The lead-bearing material can become the sacrificed anode. Lead leaching is one of the most problematic issues facing water utilities today and continued vigilance is needed to protect public health and advance our understanding of how to “Get the Lead Out.”