I am writing this time regarding PHREEQC rather than PHRQPITZ > 1. I have a data set for injection well disposal. Two aqueous streams are mixed together and then injected. In the attached file, CoolingTowerMixA.out, the calculated errors for solution 2 are rather large, >20%. Does a calculated error this large suggest problems? It's not great. Calcium and alkalinity errors will naturally affect the SI(calcite) more than errors in sodium and chloride. A beneficial factor, the SI's are log quantities, so 20% error in calcium translates to about .1 in SI(calcite) (log10(1.2)). However, a .2 error in pH translates to .2 error in SI(calcite). > I am particularly concerned with the high calculated pH value. Were this to be significantly in error all of the calculated saturation indices would be in question. I think the pH is probably about right if the water were to completely equilibrate with air. You can check, but I don't think the calculated pH is very sensitive to the analytical data for the initial solution. > 2. later on in the process I will be equilibrating the mixed stream with the existing groundwater, which has a TDS of 34,000 mg/L with chloride 18,000 mg/L and sodium of 11,000 mg/L. Will PHREEQC handle this groundwater? As opposed to PHRQPITZ? The ionic strength is a little high. I'd probably do a little checking with PHRQPITZ, but I think because it is a sodium chloride dominated water, PHREEQC and PHRQPITZ will be pretty similar. Also, if you are mixing the waters, the resulting water will tend to have a lower ionic strength. > Without documentation for PHRQPITZ PHREEQC is proving a lot easier to deal with. I can send the documentation for PHRQPITZ if you forward your address. David David Parkhurst (dlpark@xxxxxxxx) U.S. Geological Survey Box 25046, MS 413 Denver Federal Center Denver, CO 80225
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