First Step: Calculate Charge Balance Error
The first thing aqion does when you click on the Start button is to calculate the charge-balance error (CBE) of the input water. The screenshot below shows the CBE of the example water “ib.sol”.1
The output panel displays:
- CBE in percent
- sum of cations in meq/L
- sum of anions in meq/L
Now, the user has the possibility to re-adjust one chemical parameter in order to obtain complete charge balance. For this purpose you should select one of the following parameters from the corresponding pull-down list:2
|• pH value||(default)|
|• … etc.|
Note: The button Details opens a guidance for charge-balance adjustment. It provides a hint which parameter, cation or anion, should be selected to improve the discrepancy.
Second Step: Adjust Charge Balance
The example above has an error of -1.89%. If we select the parameter DIC and click on next the right screenshot pops up. It tells us that DIC is decreased:3
5.894 mM ⇒ 5.455 mM
The line below displays the amount added (as the difference of both values):
ΔDIC = -0.439 mM
A positive (negative) Δ-value signals addition (removal) of the element. The obtained solution is fully charge-balanced (and is referred to as Output 1).
In addition, aqion performs a second calculation (Output 2) to check whether minerals precipitate or not. In this example, the equilibrium solution is supersaturated with two minerals: Fe(OH)3 and Calcite. The precipitation causes the final pH change from 7.00 to 7.94.
The complete speciation of the example water “ib.sol” is presented as PowerPoint. ↩
The symbols in square braces represent the corresponding valence states. ↩
The concentration units can be switched between mg/L and mmol/L (by the dropdown field to the right of the Δ-value). ↩