AWWA JAW10082

Indexes based on water characteristics such as pH, alkalinity, and calcium concentration have been applied in corrosion control for certain types of water. However, these indexes are not direct measures of water corrosivity, but are indicators of the tendency of water to form films of calcium carbonate (CaCO3), which may be protective. The authors of this article report on the effectiveness of some common indexes for describing controlled deposition of CaCO3. Formulas for calculating the following six indexes are derived: Langelier index; Ryznar index; driving force index; aggressiveness index; momentary excess; and calcium carbonate precipitation potential. The authors conclude that the calcium carbonate precipitation potential is best suited to describe CaCO3 precipitation and dissolution. Includes 17 references , table, figures.