AWWA ACE54341

The interactions among natural organic matter (NOM), particles, and ultrafiltration membranes in combined adsorption/membrane systems were studied in this research. Three types of particles that included heated iron oxide particles (HIOPs), powdered activated carbon (PAC), and SiO2, were studied. The key performance parameters were the total organic carbon (TOC) reduction between the influent and permeate and the rate of membrane fouling. On a mass basis, PAC removed TOC from solution more efficiently than either of the other types of particles. Although TOC removal is sometimes associated with a reduction in fouling, in these systems fouling occurred more rapidly than when no PAC was present. By contrast, when HIOPs were added at a dose sufficient to achieve the same TOC removal as in the systems with PAC, fouling was significantly less severe than when PAC was present, and in fact was less severe than when no particles were added at all. Addition of SiO2 did not remove any TOC from solution, and it increased the rate of fouling. When Milli-Q water was fed to the treatment system in conjunction with each of the particles, the fouling was much less severe than when NOM was present, suggestingthat direct fouling of the membrane by the particles themselves was unlikely to be the main reason for the different effects of the particles. On the other hand, the fact that addition of PAC removed TOC but exacerbated fouling shows that the fouling cannot be explained solely on the basis of NOM interactions with the membrane. Scanning electron microscope (SEM) images of the cake layers suggest that severe fouling is associated with the formation of a continuous layer of material across themembrane surface. Precipitated or coagulated NOM near the PAC particles binds those particles to the membrane surface in a manner that apparently allows the particles to contribute to fouling. When it contacts HIOPs in the cake layer, NOM seems to bind the particles to one another but not to the membrane, allowing the membrane to remain more permeable to water. Includes 11 references, table, figures.

Product Details

Edition:

Vol. - No.

Published:

06/01/2001

Number of Pages:

9

File Size:

1 file , 870 KB