TP22-10: Interpreting and Applying Scale Indices and Saturation Ratios to Identifying and Solving Water Treatment ChallengesPredictive models and tests have evolved significantly since the marble test of the early twentieth century, the simple driving force indices such as the father of all indices, the Langelier Saturation Index1 in the 1930s, through the early speciation engines of the 1970s and 1980s, 2,3,4 and onto the high ionic strength models of the twenty first century. 5,6 Other models such as the Calcium Carbonate Precipitation Potential7 and Momentary Excess,8