hyd-RO-dose: Old Standards and Sophisticated Indices

We all have favorite, or at least familiar indices which assist in the assessment of the scale potential of a water, and which provide some insight into the impact of concentrating it, heating it, or changing pH. The common indices provide an excellent starting point for evaluating a water chemistry and scale potential.

Prior to the advent of cost effective personal computers, sophisticated indices were beyond the reach of most water chemists. The indices and calculation methods practical for manual use are simplifications which include assumptions that can cause misleading interpretations, especially in high TDS brines, and limit the applicability of the indices.

Use hyd-RO-dose to Minimize

Scale Potential with Acid Feed

Though helpful, the indices and calculation methods practical for manual use are simplifications which include assumptions that can cause misleading interpretations, and limit the applicability of the indices to a single water, or similar waters.

The old standards provide insight into scale potential for single scales. They are limited to simple estimation methods, and do not take into account phenomena such as "Common Ion Effects." Sophisticated indices such as ion association model saturation levels account for these effects and can be calculated for most foulants.

Ion association model indices also provide a more realistic view of scale potential than the old standbys. They base their calculations upon free ion concentrations rather than the total analytical values used for most indices.

In natural waters, calcium (for example) is not typically found as 100% free calcium. A portion of the calcium may be bound to sulfate, another portion of the total may be tied up by bicarbonate, hydroxide or other species with which it associates. Ions in water are typically associated with other ions. Indices calculated based upon total ion present (e.g. total analytical calcium) can be misleading.

In high TDS waters, they can grossly over estimate the driving force for scale formation and growth. The ion association model indices overcome this shortcoming by estimating the concentration of free ions, and calculating indices using the free concentration rather than the total. Ion association model indices improve the realism, and the accuracy, of scale prediction in this manner.

hyd-RO-dos uses an ion association model to extend the applicable ionic strength for calculations, and to provide consistent, reproducible indices for common, and not so common, scale forming species.

Use hyd-RO-dose to Evaluate the Ability of

Scale Inhibitors to Increase Recovery

Scale Inhibitor Models Available for the hyd-RO-dose Series

Acknowledgments
Acumer is a trademark of the Rohm & Haas Company
Aquatreat is a trademark of the ALCO Chemical Division of National Starch
Bayhibit is a trademark of Bayer
Belclene, Belcor, Belsol, and Belsperse are trademarks of FMC
Dequest is a trademark of Monsanto Chemical Company
Goodrite is a trademark of the BFGoodrich Company
Versa is a trademark of the National Starch and Chemical Company
hyd-RO-sat and hyd-RO-dose are trademarks of French Creek Software

ION ASSOCIATION MODEL SATURATION LEVELS AND MOMENTARY EXCESS VALUES CALCULATED BY 

hyd-RO-dose (version 6) Pricing