Reconciliation Options in OLI Software
When reviewing laboratory analysis of water samples, it is quite common for the positive ions (cations) and the negatively charged ions (anions) in solution to not balance. This may be due to the precision limits of the various experimental procedures used to measure the ions - i.e. some ions may not have been analyzed. These solutions must have a neutral charge. Stream Analyzer will adjust/modify inflows in order to balance the charges and make the solution neutral. This adjusting procedure is referred to as Reconciliation. The pH and the alkalinity of the solution are frequently measured. However, since the analysis is experimental and subject to errors, the pH and alkalinity values that are calculated by the Water Analysis tool may be different from what is measured experimentally. Stream Analyzer can also reconcile this difference.
There are four options for reconciliation:
- No Reconcile: The software will run an electroneutrality reconciliation only, and then compute the water properties such as pH, density, etc., based on the entered concentration of neutral, cations, and anions species. In the No Reconcile option you may allow the program to pick the species to adjust for electroneutrality or you may manually choose the species to perform the adjustment.
- Reconcile pH: The software will run both an electroneutrality and pH reconciliation. This type of reconciliation will match your recorded pH. Additionally, the software will compute the water properties such as, density, electrical conductivity, etc. The pH of the solution is automatically adjusted by the software by adding either HCl or NaOH, or you may select your preferred acids and bases to adjust the pH.
- Measured pH and Alkalinity: The purpose of the Measured pH and Alkalinity reconciliations is to match the computed pH and alkalinity values with those you measured (TIC is unknown). The software will run an electroneutrality, pH and alkalinity reconciliation. Additionally, the software will compute the water properties such as density, electrical conductivity, etc. The pH of the solution is automatically adjusted by the software by adding either HCl or NaOH or you may select your preferred acids and bases to adjust the pH. The Alkalinity is automatically calculated by the software, using CO2 as the alkalinity titrant, H2SO4 as the alkalinity pH titrant and 4.5 as the alkalinity end point pH. You can also change a different alkalinity pH titrant if you prefer. However, you cannot change the CO2 as the alkalinity titrant for the alkalinity adjustment.
- Measured pH, Alkalinity, TIC: The purpose of this reconciliation is to match the measured pH, alkalinity and Total Inorganic Carbon (TIC). The pH of the solution is automatically adjusted by the software by adding either HCl or NaOH or you may select your preferred acids and bases to adjust the pH. The TIC is automatically calculated by the software, using CO2 as the titrant, H2SO4 as the pH titrant and 4.5 as the end point pH. The (total) Alkalinity is adjusted by the software by adjusting the acetate concentration (organic acids) to match the target Alkalinity. The Alkalinity is adjusted by adding or removing acetic acid. In this calculation, you cannot change the CO2 or Acetic Acid for the alkalinity adjustment, these are fixed by the software.
Additionally, there is the option (button) to Calculate Alkalinity. It is important to note, that this is only an alkalinity calculation based on the concentration entered, it is not an alkalinity reconciliation. This option is not enabled when doing any alkalinity reconciliation.