Effects of adsorbents on membrane fouling by natural organic matter

Fouling by natural organic matter (NOM) is a major impediment to cost-effective operation of membrane processes in water treatment. This research investigated the removal of NOM by three adsorbents: heated iron or aluminum oxide particles (HIOPs and HAOPs, respectively) and powdered activated carbon (PAC). Although PAC removed a larger fraction of the DOC than did either HAOPs or HIOPs, it adsorbed non-fouling molecules preferentially over foulants, whereas the opposite was true for the metal oxide particles. In addition, when the oxide adsorbents were pre-deposited on a microfiltration membrane, foulants that were not adsorbed in batch tests were effectively removed from the solution before it reached the membrane, leading to excellent performance with respect to both NOM removal and fouling. SEM images showed that membranes under a layer of HAOPs and HIOPs were virtually as clean as a pristine membrane.