Compilation of a pH adjustment algorithm

A pH adjustment algorithm for use in a proposed underground lime dosing process control system was completed for Anglo American Research Laboratories. The algorithm calculates the amount of lime required for pH adjustment in units of mg/l of Ca(OH)₂ based on a variable pH input and set temperature, sodium, magnesium, calcium, chloride, sulphate, conductivity, H₂CO₃ (total) alkalinity and desired pH.

The algorithm will provide good results for waters with similar chemical analyses as the one provided by Anglo American Research Laboratories. However, should the analysis of a particular water deviate from this, the characterisation of such a water cannot be accomplished accurately with only one input parameter (in this case pH). The pH, temperature, ionic nature of the water (total dissolved solids or conductivity) and a parameter characterising the carbonate system (for example H₂CO₃ alkalinity) are required for complete characterisation of a low salinity water. For complete characterisation of a medium salinity water (total dissolved solids above 1 000 mg/l), the concentrations of the species constituting the principal ionic matrix (sodium, magnesium, calcium, chloride and sulphate) must be incorporated as well.

© softchem 1996