Abstract
Nanofiltration is considered one of the most promising technologies for the removal of hardness as well as disinfection-by-products precursors. In this study, we set up a benchscale nanofiltration apparatus to investigate the effect of the operational parameters (e.g., applied pressure and feed water recovery) on hardness removal and inorganic fouling. Synthetic aqueous solutions prepared by calcium sulfate are used in the nanofiltration experiments. Operating pressure is accurately controlled from 20 to 100 psi using a gear pump. It is observed that the hardness rejection remains relatively constant at low feed water recovery (< 70 %). At higher recovery (>70 %), however, the rejection decreases sharply with the increase of recovery. Increased operating pressure results in greater hardness rejection due to the increased permeate flux and greater concentration factor in the feed water. A transport model based on mass balance has also been developed to simulate the hardness rejection behavior under the typical operating conditions of nanofiltration. The model results are in agreement with the experimental observations.
