COMPUTING SI AND CCPP USING SPREADSHEET PROGRAMS

Lotus 1-2-3(R) worksheets for calculating the calcite saturation index (SI) and calcium carbonate precipitation potential of a water sample are described. A simplified worksheet illustrates the principles of th e method, and a more complex worksheet suitable for modeling most pota ble water sources is briefly described. Both worksheets include ion pa iring and adjustments of equilibrium constants for temperature and ion ic strength. For several test cases with a wide range of temperature, alkalinity, pH, and calcium concentration, the worksheet SI values dif fered <1 percent from those computed by WATEQX. For water differed mod elling spreadsheets have several advantages compared with large equili brium codes: flexible input and output, ease of maintaining the thermo dynamic database, and relatively small memory and mass-storage require ments. Modeling of archived chemical data is possible through the comb ination of database management and computational capabilities of many commercially available programs. The worksheets can be obtained from t he authors.