AWWA WQTC62407

Of 90 lead service line or lead pig-tail specimens received from 34 different United Statespublic water systems analyzed by US Environmental Protection Agency (USEPA), at least 20 show definitive amounts of tetravalentlead compounds, of the forms α- and ß-PbO₂. These 20 specimens represent 9 systems, or 26%of the systems investigated, and includes both ground and surface waters, and a diverse array ofpHs and alkalinities. These solids have substantially different solubilities and responses to pH,carbonate concentration, disinfectant type, and disinfectant concentration than the well-knowndivalent lead carbonate, hydroxycarbonate and [hydroxyl]phosphate compounds that have beenthe basis for virtually all of the prior guidance on the control of lead release into drinking water.Stable tetravalent lead compounds are associated with very low lead release levels (Schock et al.,2001; Schock & Giani, 2004; Lytle & Schock, 2005). Therefore, understanding the waytetravalent lead occurs in the scales of lead pipe is of utmost importance in optimizing corrosioncontrol strategies, and guarding against accidental episodes of high lead concentrations thatcould result from treatment changes or from water blending in the distribution system thatdissolve those Pb(IV) phases.For this study, pipe deposits were analyzed primarily using three methodologies: powderX-ray diffraction (XRD); X-ray Absorption Near-Edge Spectroscopy (XANES); and opticalmicroscopy. Supplemental elemental analysis by multi-acid digestion with inductively-coupledplasma spectroscopy and scanning electron microscopy were available for some of the samples.Further understanding of the environment of formation of PbO₂ was achieved by laboratoryoxidation and solubility experiments for lead in water, and by the use of equilibrium speciationcomputational models. Includes 20 references, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2005

Number of Pages:

15

File Size:

1 file , 2.2 MB