A serial filtration investigation of membrane fouling by natural organic matter

It is proposed that the NOM exists in the raw water in units with a pseudo-equilibrium size distribution. Some of these units collect on the membrane and serve as nuclei for accretion and coalescence with other units. Immediately after passage through the membrane, the permeate is depleted in larger NOM units, but if the permeate is stored, a size distribution more like that in the unfiltered water is eventually re-established. Nevertheless, at least for the samples studied here, fouling of the membrane in the second filtration step progressed much less rapidly than in the first step, indicating that the NOM units responsible for fouling were selectively removed.