Anoop Chengara

Hello, I have a high pH water (~ 12) that I am trying to neutralize to pH 8 by sparging CO2 into. I would like to calculate the pH vs CO2 added to the system. I followed the 'Gas Buffer' case https://academy.gwb.com/buffers.php#TASK3 to set up the React model. I used the CO2 with HCO3 equilibrium in the Basis pane, but didn't know how to set up the Reactant pane properly. So I used CO2(g) as the reactant and get the error as seen in the attachment. The largest residual is on the Cl- and Na+ ions. Interestingly, when I do the same calculation by replacing the CO2 with HCl as titrant (1000 mg/L) and remove the CO2 with HCO3 equilibrium constraint, the calculation is completed, despite the fact that Cl- is added in the titration (please see attachment). I am attaching both the React files for your consideration. Can you please suggest how I can overcome this error and run the case with CO2 as titrant? Thank you Anoop GSS_LF MVC BD_HCl.rea GSS_LF MVC BD_HCl CO2.rea

Hello Jia Thank you for the pointer on the alkalinity calculation. After following the example listed in the GWB Academy, I have a couple of questions: 1. Why is the 'No Precipitation' option selected in the alkalinity titration (Config --> Options)? 2. I am attaching an example file for which the water chemistry reported had an unusually high Total Alkalinity of 4687 mg/L as HCO3- which does not reconcile with the measured pH of 6.1. In practice, Sulfuric Acid is used as the titrant and can result in sulfate scale precipitation, giving erroneous results. So I compared 4 React cases with 2 titrants (HCl and H2SO4) using both options (Allow Precipitation and No Precipitation). I find that irrespective of titrant (HCl or H2SO4), the prediction of carbonate alkalinity is the same for a given option (either Allow Precipitation or No Precipitation). Further, the prediction of carbonate alkalinity is around 650 mg/kg CaCO3 when 'Allow Precipitation' is checked vs 1800 mg/kg CaCO3 when 'No Precipitation' is permitted. Why is there such a difference, despite the fact that in either case of titrant, carbonate species are not above saturation? Thank you Anoop GSS_SSAU - Average.rea SSAU Alkalinity Reconciliation.pptx

Hello, Please disregard this message. I could get it to converge after removing the Carbonate Alkalinity field entry. Thank you.

Hello, I am having trouble with convergence of charge balance in SpecE8 of the water sample labeled M66. The Mg and Na seem to have the largest residuals, but the water analysis is not expected to be so inaccurate. I have also modified the Na concentration to reflect proper charge balance as calculated by other software e.g. Scale Soft Pitzer. The convergence problem still persists. Can you please suggest corrective steps? I am attaching the GSS spreadsheet. Thank you Anoop GOM King Dumpflood.gss