AWWA JAW55361

With models currently available, water utilities are hard-pressed to accurately predict copper (Cu) liberation to drinking water. This study used thermodynamic models in conjunction with experimental and field data to analyze concentrations of Cu, anions, and cations. Special attention was focused on the aging process of Cu scales on the inner walls of copper pipes; precipitation and dissolution were predicted as the main causes of aging for these scales. In addition, scales usually contained more than one compound - a finding that was attributed to temperature changes, variability of water composition, long stagnation periods, and aging. As the aging process proceeds, parts of a young scale's surface area may be covered and blocked for further reaction by a precipitate. During long stagnation periods, such factors as changes in pH, oxygen, and carbon dioxide concentrations and precipitation of calcium solids may induce a different Cu compound precipitate. Data from key parameters such as pH, alkalinity, hardness, temperature, pipe age, and sulfate concentration can enable utilities to better predict Cu liberation to drinking water. This in turn may help water providers understand how treatment options and mixing of water of different composition affects the liberation of Cu to drinking water and, ultimately, the concentration of Cu in stagnant water. Includes 24 references, tables, figures.

Product Details

Edition:

Vol. 93 - No. 11

Published:

11/01/2001

Number of Pages:

10

File Size:

1 file , 380 KB