Combined effect of scale-forming ions and humic acid on nanofiltration membrane fouling.

In this study, a model for the progress of membrane fouling due to scale formation in nanofiltration systems is presented. The model was developed based on the surface blockage equation to estimate flux as a function of volume concentration factor (VCF). Experiments were carried out to apply the model using CaSO₄ saturated solution. Humic acid was used as a background organic matter that may interfere with the scale formation. The model could match the experimental data well with the overall R² value of 0.95 for more than 1,000 data points. The addition of the humic acid affected the changes in flux with VCF. The model parameters were different for different humic acid concentration. It is likely that the humic acid retards the scale formation rate by changing the crystallization kinetics. The rate of flux decline and VCF increase were also estimated as a function of the humic acid concentration. [ABSTRACT FROM AUTHOR]