Lead can be released to drinking water from corrosion and dissolution of lead-containing
pipes, fittings and solders in existing old drinking water service lines.
Resulting high lead concentrations can cause adverse health effects. Pb(II) solids and
Pb(IV) oxides, discovered as the corrosion products covering the walls of lead pipes, are
the major contributors to lead release. Among them, Pb(II) solids are presumed to have
higher solubility relative to Pb(IV) oxides. Thus, switching the residual disinfection
method from chlorine to chloramines can lower the oxidation-reduction potential (ORP),
thereby enabling the breakdown of Pb(IV) oxides and consequently higher lead
concentration. However, there is limited data on the equilibrium solubility or dissolution
and transformation rates of Pb(IV) oxides. Also, substantial research on the water
chemistry conditions in which Pb(IV) oxides form and stabilize over time is needed for a
scientific strategy of controlling lead concentration in drinking water distribution systems.
In this research, the equilibrium solubility, dissolution and transformation rates of pure
Pb(IV) oxides are investigated as a function of pH, dissolved inorganic carbon (DIC),
orthophosphate, and the presence of chloramines. New lead pipes are conditioned using
chlorine to form Pb(IV) oxides, and release rates of lead from them are investigated
under varied water chemistry, stagnation time and flow velocity. The lead corrosion
products and possible transformation of them are characterized with respect to
mineralogy, size, morphology, surface area, and molecular structure. Water chemistry
conditions, including pH, ORP in terms of chlorine concentration, lead concentration and
DIC, in which a-PbO2 and ß-PbO<sub>2</sub> form and stabilize over time are also studied. Includes 11 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 880 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 11 |
| Published : | 11/01/2008 |
