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