NOM fouling mechanisms in a hybrid adsorption/membrane system

This study investigated the distribution of NOM, and its foulant fraction, in hybrid adsorbent/membrane systems. The adsorbent used in the work was heated aluminum oxide particles (HAOPs). Color changes, SEM images, and analysis of the carbon content in the HAOPs layer support the view that NOM molecules can form a gel layer at the surface of the HAOPs layer, but that this gel layer does not contain the majority of the removed species or the foulant. Rather, the HAOPs layer acts as a short, packed bed, with steadily less adsorbate removed in each successive layer of particles. In constant flux systems, the amounts of NOM and foulant that can be removed are approximately proportional to the mass of HAOPs in the layer. Fouling is attributed to the small, but steadily increasing, amount of NOM that is rejected by the membrane after passing through the HAOPs layer. This NOM appears to be relatively easy to remove by disruption of the HAOPs or rinsing of the membrane surface. The system functions well when either fresh or saline water is the feed.