When calculating antiscalant dosage, inhibition of all scales must be considered. Potentials scales that can form are:
metal hydroxides (iron, aluminum)
Calcium hardness alone cannot be used to determine scaling tendency, as it must combine with an anion to form a scale. In order to calculate the antiscalant dosage, a comprehensive water analysis must be performed that contains the following parameters:
Ca, Mg, Ba, Sr, Fe, Al, Mn, Na
Alkalinity, SO4, F, PO4, SiO2
Other Required Information:
Feed water pH (measured upon collection at site), Feed water Temperature (measured upon collection at site), %Recovery, Membrane Salt Rejection (available on membrane cut sheet), and system configuration (# stages, # Pressure Vessels/stage)
Once all the above information is available, the scaling potential can be calculated by your antiscalant supplier, and the appropriate antiscalant can be selected with a corresponding dosage.